Characteristics of a Step Motor
Frequently Asked Questions
• Step motors are constant power devices.
• As the stepr motors speed increases, torque decreases.
• Maximum torque for most step motors is when the motor is fixed, but the important aspect of step motors is the torque when rotating (spinning).
• Torque curves (performance curve of distinuishing step motors) can be extended by current limiting step motor drivers (see our web site for compatible step motors and driver models).
• Step motors exhibit some vibratory characteristics, more than other motor types. (If vibration is a problem, consider another technology).
• The vibration seen in step motors is due to the fact that the takes discrete steps and this tends to create a snap in the step motor rotor, as it moves from one position to the other.
• Proper sizing and pairing the step motors with the step motor driver will help reduce vibration
• Failure to correctly size a step motors application can cause the motor to lose torque and change direction, at certain speeds. (This problem can be greatly reduced or eliminated by accelerating rapidly the speeds that are problematic. Frictional damping the step motor system or using a micro step motor driver combination may completely solve this problem.
• Stepper motors that are constructed with a high amount of phases are capable of smoother operation, or the same effect can be accomplished using a microstep drive technique.
Anaheim Automation carries a broad line of step motors, as well as step motor drivers and controller. Specials and customization services are also available, should your application require an exact step motor distinuishingation.
Step Motor Types
There are three different fundamental types of Step Motor products. The Step Motor products types vary by structure and in how they operate. Each of the Step Motor products attempt to present their own solutions to different applications. The three different standard designs of Step Motor products include the Variable Reluctance, Permanent Magnet, and Hybrid.
Variable Reluctance (VR) Step Motor products:
Variable Reluctance Step Motor products are known for having soft iron multiple rotor and a wound stator. The Variable Reluctance Step Motor products hold no detent torque. They normally operate in step angles from 5 to 15 degrees at fairly high step rates. In Figure 5, whenever phase A is energized, four rotor teeth line up along with the four stator teeth of phase A by magnetic attraction. The next step is taken when A is switched off and phase B is energized, rotating the rotor clockwise 15°; Continuing the sequence, C is turned on next and then A again. Counter clockwise rotation is achieved when the phase order is reversed.
Permanent Magnet (PM) Step Motor products:
The second type of Step Motor products are the Permanent Magnet Stepper motors.These Step Motor products are diverse from the other two considering they have permanent magnet rotors and no teeth; the rotors are magnetized verticle with respect to the axis. The rotor is attracted to the magnetic poles and therefore it rotates, whenever the four phases are energized in sequence. The motor demonstrated in Figure 6 uses 90 degree steps as the windings are energized in sequence ABCD. Permanent Magnet Step Motor products normally have step angles of 45 to 90 degrees and have a tendency to step at relatively low rates, but produce high torque and excellent damping characteristics.
Hybrid Step Motor products:
Hybrid Step Motor products combine qualities from the permanent magnet and variable reluctance Step Motor products. The Hybrid Step Motor products have most of the chosen features of each. These Step Motor products have an exceptional holding and dynamic torque, a high detent torque, and they can operate in high Stepper speeds. Hybrid Step Motor products possess step angles of 0.9 to 5.0 degrees, which is natural. Bi-filar windings are commonly provided to these Step Motor products so a single power supply can be made to power the Step Motor products. The rotor will rotate in increments of 1.8 degrees if the phases are energized 1 at a time in the order they are indicated at. These Step Motor products can be driven in two phases at a time to yield greater torque. Hybrid Step Motor products can be be driven by 1 then two then 1 phase to produce half steps of 0.9 degree increments.
Bipolar Stepping Motor Basics
A bipolar stepping motor (additionally referred to as a step or stepping motor) is an electromechanical apparatus achieving mechanical movements through conversion of electrical pulses. Stepper motors are driven by digital pulses rather than by a continuous applied voltage. Unlike conventional electric motors which rotate continuously, bipolar stepping motors rotate or step in specific angular increments. A bipolar stepping motor is most commonly used for position control. With a bipolar stepping motor/driver/controller system design, it is assumed the bipolar stepping motor will follow digital instructions. One important aspect of bipolar stepping motors is their lack of feedback to maintain control of position. It is this lack of feedback which classifies bipolar stepping motors as open-loop systems.
Stepper Motors Applications
Although Stepper Motors have been overshadowed in the past by servo systems for motion control, it now is emerging as the conventional technology in preffered and preffered areas. The better factor in this trend towards Stepper Motors is the prevalence of digital control, and the emergence of the microprocessor.
Today we have numerous Stepper Motors applications all around us. Stepper Motors are made in printers (paper feed, print wheel), disk drives, photo-typesetting, X-Y plotters, clocks and watches, factory automation, aircraft controls, and numerous other applications. The ingenuity and further advances in digital technology from researchers will continue to extend the list of applications in which Stepper Motors will be made.
Stepper Motors Common Causes for Failure
Frequent Causes for Stepper Motors and/or Stepper Driver Failure
NOTE: Always read the condition sheet/user's guide that accompanies each product
Problem: Intermittent or erratic basic stepper motors or drivers operation.
Solution: This is the most frequent cause of failure and 1 of the most problematic to detect. Begin by checking to insure that all connections are snug between basic stepper motors and drivers. Evidence of discoloration at the terminals/connections, may denote an insecure connection. When replacing a basic stepper motor, driver or Driver Pack in a motion control system, be sure to inspect all terminal blocks and connectors. Check cabling/wiring for precision. Stress basic stepper motor wiring and connections for amiss conditions and check with an ohmmeter.
Problem: Standard Stepper motor wires were disconnected while the driver was forceed up.
Solution: Avoid performing any service to the basic stepper motors or drivers while the force is on, especially in regard to motor connections. This precaution is critical for both the driver, as well as the technician/installer.
Problem: Inenough system performance.
Solution: Check to see if the wire/cables are too lengthy. Keep wire/cable to the standard stepper motors under 25 feet in length. For applications where the wiring from the basic stepper motors to the stepper drivers exceeds 25 feet, please touch the factory for instructions, as it is likely that temporal voltage protection devices will be required. Another possibility is that the standard stepper motor lead wires are of a gauge that is too short. Do not match your cable wires to the gauge size the standard stepper motor lead wires. Anaheim Automation suggests using a shielded cable for such wiring (bought separately). Additionally, check the age of your standard stepper motor, as with time and use, standard stepper motors lose most of their magnetism which affects performance. Commonly 1 can expect 10,000 operating hours for basic stepper motors (approximately 4.8 years, running 1 eight-hour shift per work day). Also, make certain that your basic stepper motor and driver combination is a acceptable match for your application. Contact the factory, should you have any concerns.
Problem: The basic stepper motor has a shorted winding or a short to the motor case.
Solution: It is likely that you have a abnormal basic stepper motor. Do not attempt to repair motors. Opening the basic stepper motor case may de-magnetize the motor, causing poor performance. Opening of the basic stepper motor case will also void your warranty. The motor windings can be examed with an ohmmeter. As a rule of thumb, if the basic stepper motor is a frame size of NEMA 08, 11, 14, 15, 17, 23, or 34 and the warranty period has expired, it is not cost-effective to return these basic stepper motors for repair. Call the factory if your suspect a abnormal basic stepper motor that is still under warranty, or if it is a NEMA size 42 or a K-series motor.
Problem: The basic stepper motor driver or Driver Pack is over-heating.
Solution: Ventilation and cooling accommodations are vital - failure to provide enough airflow will affect the basic stepper motor driver's performance and will shorten the life of the driver. Keep driver temperatures below 60 degrees Celsius. To maintain acceptable airflow, use fans, heat sink material, and base plates, so not to exceed the elevatedest temperature rating of the basic stepper motors, drivers or controllers. Be mindful of temperatures inside cabinets and enclosures where stepper drivers may be mounted.
Problem: Environmental factors are less than normal.
Solution: Environmental factors, such as welding, chemical vapors, moisture, humidity, dust, etc., can harm both the electronics and the basic stepper motors. Protect drivers, controllers and basic stepper motors from environments that are wearing, contain voltage spikes, or prevent acceptable ventilation. For AC lines that contain voltage spikes, a line regulator (filter) will be required.
Problem: Pulse rates (Clock or Step) to the driver are too elevated.
Solution: The typical half-step driver can drive basic stepper motors at a elevatedest rate of 20,000 pulse per 2nd. Pulse rates of above 60,000 pulses per 2nd can harm the driver. See distinct condition sheets for the motor and driver combination for optimum performance.
Problem: The basic stepper motor is stalling.
Solution: In many cases, stalling the motor causes a enormous voltage spike that often harms the phase transistors on the driver. Some drivers are built to protect itself from such an occurrence. If not, Transient Suppression Instruments can be added externally. Consult the factory for further info.
Problem: The basic stepper motor is back-driving the driver.
Solution: A basic stepper motor that is being turned by a load creates a back EMF voltage on the driver. Higher speeds will produce elevateder voltage levels. If the rotational speed gets overly elevated, this voltage might cause harm to the driver. This is especially dangerous when the motor is back-driven while the driver is still on. Put a mechanical stop or brake in applications that might be subject to these phenomena.
General Safety Considerations for Stepper Motor Applications
The following safety considerations must be observed during all stages of operation, service and repair. Failure to comply with these precautions violates safety basics of design, manufacture, and intended use of basic stepper motors, drivers and controllers. Even well built products, operated or installed imsuitablely, can be unpredictable. Safety precautions absolutely must be observed by the user with respect to the load and operating environment. The customer is responsible for suitable selection, installation and operation of the products bought.
• Use caution when handling, examining, and adjusting during installation, set-up and operation
• Service should not be performed with force applied
• Exposed circuitry should be suitablely guarded or enclosed to prevent unauthorized human touch with live circuitry
• Many products should be securely mounted and enoughly grounded
• Provide enough air flow and heat dissipation
• Dont operate in the presence of flammable gases, vapors, liquids or dust
NOTE: Please Use a RMA Form should you need to return a product for REPAIR. This form can be found in Support, Forms, RMA Request on this web site.
Stepper Motors Common Causes for Failure
Frequent Causes for Stepper Motors and/or Stepper Driver Failure
NOTE: Always read the specification sheet/user's guide that accompanies each product
Problem: Intermittent or erratic step motors or drivers operation.
Solution: This is frequently the cause of failure and 1 of the most intricate to detect. Begin by checking to insure that all connections are tight amidst step motors and drivers. Evidence of discoloration at the terminals/connections, could denote a free connection. When replacing a step motor, driver or Driver Pack in a motion control system, be sure to inspect all terminal blocks and connectors. Check cabling/wiring for certainty. Stress step motor wiring and connections for weak quality conditions and check with an ohmmeter.
Problem: Step motor wires were disconnected while the driver was powered up.
Solution: Avoid performing any service to the step motors or drivers while the power is on, especially in regard to motor connections. This precaution is crucial for both the driver, as well as the technician/installer.
Problem: Weak system performance.
Solution: Check to see if the wire/cables are too lengthy. Keep wire/cable to the step motors under 25 feet in length. For applications where the wiring from the step motors to the stepper drivers exceeds 25 feet, please contact the factory for instructions, as it is likely that transient voltage protection instruments will be required. Another possibility is that the step motor lead wires are of a gauge that is too little. Do not match your cable wires to the gauge size the step motor lead wires. Anaheim Automation suggests using a shielded cable for such wiring (bought separately). Additionally, check the age of your step motor, as with time and use, step motors lose most of their magnetism which affects performance. Generally 1 can expect 10,000 operating hours for step motors (approximately 4.8 years, running 1 eight-hour shift per work day). Also, make certain that your step motor and driver combination is a excellent match for your application. Contact the factory, should you have any concerns.
Problem: The step motor has a shorted winding or a short to the motor case.
Solution: It is likely that you have a damaged step motor. Do not attempt to repair motors. Opening the step motor case could de-magnetize the motor, causing weak performance. Opening of the step motor case will also void your warranty. The motor windings can be tested with an ohmmeter. As a rule of thumb, if the step motor is a frame size of NEMA 08, 11, 14, 15, 17, 23, or 34 and the warranty period has expired, it is not cost-effective to return these step motors for repair. Call the factory if your suspect a damaged step motor that is still under warranty, or if it is a NEMA size 42 or a K-series motor.
Problem: The step motor driver or Driver Pack is over-heating.
Solution: Ventilation and cooling accommodations are crucial - failure to provide adequate airflow will affect the step motor driver's performance and will shorten the life of the driver. Keep driver temperatures below 60 degrees Celsius. To maintain excellent airflow, use fans, heat sink material, and base plates, so not to exceed the foremost temperature rating of the step motors, drivers or controllers. Be mindful of temperatures inside cabinets and enclosures where stepper drivers could be mounted.
Problem: Environmental factors are less than normal.
Solution: Environmental factors, such as welding, chemical vapors, moisture, humidity, dust, etc., can damage both the electronics and the step motors. Protect drivers, controllers and step motors from environments that are wearing, contain voltage spikes, or prevent excellent ventilation. Anaheim Automation provides products in several line voltage ranges. For AC lines that contain voltage spikes, a line regulator (filter) will likely be required.
Problem: Pulse rates (Clock or Step) to the driver are too colossal.
Solution: The typical half-step driver can drive step motors at a foremost rate of 20,000 pulse per second. Pulse rates of above 60,000 pulses per second can damage the driver. See exclusive specification sheets for the motor and driver combination for foremost performance.
Problem: The step motor is stalling.
Solution: In most cases, stalling the motor causes an abundant voltage spike that often damages the phase transistors on the driver. Most drivers are built to protect itself from such an occurrence. If not, Transient Suppression Instruments can be added externally. Consult the factory for further data.
Problem: The step motor is back-driving the driver.
Solution: A step motor that is being turned by a load creates a back EMF voltage on the driver. Higher speeds will produce colossaler voltage levels. If the rotational speed gets intensely colossal, this voltage might cause damage to the driver. This is especially dangerous when the motor is back-driven while the driver is still on. Put a mechanical stop or brake in applications that might be subject to these phenomena.
General Safety Considerations for Stepper Motor Applications
The following safety considerations should be observed during all stages of operation, service and repair. Failure to comply with these precautions violates safety standards of design, manufacture, and intended use of step motors, drivers and controllers. Anaheim Automation, Inc. assumes no liability for the customer's failure to comply with these requirements. Even well built products, operated or installed improperly, can be risky. Safety precautions should be observed by the user with respect to the load and operating environment. The customer is responsible for proper selection, installation and operation of the products bought from Anaheim Automation, Inc.
• Use caution when handling, testing, and adjusting during installation, set-up and operation
• Service should not be performed with power applied
• Exposed circuitry should be properly guarded or enclosed to prevent unauthorized human contact with live circuitry
• All products should be securely mounted and appropriately grounded
• Provide adequate air flow and heat dissipation
• Do not operate in the presence of flammable gases, vapors, liquids or dust
NOTE: Please Use a RMA Form should you need to return a product for REPAIR. This form can be found in Support, Forms, RMA Request on this web site.
Stepper Motors Type
There are three contrasting fundamental types of Stepper Motors. The Stepper Motors types vary by construction and in how they function. Each of these types of Stepper Motors provides a solution to an application in a contrasting way. The three contrasting fundamental types of Stepper Motors include the Variable Reluctance, Permanent Magnet, and Hybrid.
Variable Reluctance (VR) Stepper Motors
Variable Reluctance Stepper Motors are known for having soft iron multiple rotor and a wound stator. The Variable Reluctance Stepper Motors commonly operate in step angles from 5 to 15 degrees at comparably elevated step rates. They additionally contain no detent torque. In Figure 5, when phase A is energized, 4 rotor teeth line up with the 4 stator teeth of phase A by magnetic attraction. The next step is taken when A is turned off and phase B is energized, rotating the rotor clockwise 15 degrees; Continuing the sequence, C is turned on next and then A again. Counter clockwise rotation is achieved when the phase order is reversed.
Permanent Magnet (PM) Stepper Motors
Permanent Magnet Stepper Motors differ from Variable Reluctance Stepper Motors by having permanent magnet rotors with no teeth. These rotors are magnetized perpendicular to the axis. When the 4 phases are energized in sequence, the rotor rotates as it is attracted to the magnetic poles. The motor shown in Figure 6 will take 90 degree steps as the windings are energized in sequence ABCD. Permanent Magnet Stepper Motors commonly have step angles of 45 to 90 degrees and tend to step at approximately inferior rates, but produce colossal torque and admirable damping characteristics.
Hybrid Stepper Motors
Hybrid Stepper Motors combine qualities from the permanent magnet and variable reluctance Stepper Motors. The Hybrid Stepper Motors have some of the desirable features of each. These Stepper Motors have a colossal detent torque, admirable holding and dynamic torque, and they can operate in colossal Stepper speeds. Step angles of 0.9 to 5.0 degrees are normally seen in Hybrid Stepper Motors. Bi-filar windings are commonly supplied to these Stepper Motors so a single power supply can be used to power the Stepper Motors. The rotor will rotate in increments of 1.8 degrees if the phases are energized 1 at a time in the order they are displayed at. These Stepper Motors can be driven in two phases at a time to yield better torque. Hybrid Stepper Motors can additionally be driven by 1 then two then 1 phase to produce half steps of 0.9 degree increments.
Stepper Motors Disadvantages
• Low efficiency (Step motors attract a abundant amount of power regardless of the load)
• Torque drops switfly with speed (torque is inversely corresponding of speed)
• Prone to resonance* (Microstepping allows for even motion)
• No feedback to denote missed steps
• Low torque-to-inertia ratio
• Cannot accelerate loads very immediately
• Motor gets very hot in elevated performance configurations
• Motor will not “pick up” after momentary overload
• Motor is noisy at moderate to elevated speeds
• Low output power for size and weight
Resonance-is inherent in the design and operation of all stepping motors and occurs at particular step rates. It is the combination of slow stepping rates, elevated rotor inertia, and elevated torque which produce ringing as the rotor overshoots its aimed angular displacement and is pulled back into position causing resonance to occur. Adjusting either one of the 3 parameters –inertial load, step rate, or torque- will reduce or eliminate resonance. In sensible practice, the torque parameter is more controllable using microstepping. In microstepping mode, power is devoted to the stator windings accumulatively which causes torque to slowly build, reducing overshoot and as a result reducing resonance.
Stepper Motors Mode
There are 3 excitation modes that are frequently used with Stepper Motors. The Stepper Motors modes are the full-step, half-step- and micro-step.
Stepper Motors - Full-Step
In full step operation, Stepper Motors step through the normal step angle e.g. 200 step/revolution motors take 1.8 steps while in half step operation, 0.9 steps are taken. There are two kinds of full-step modes. Single phase full-step excitation is where Stepper Motors are operated with only 1 phase energized at-a-time. This mode should only be used where torque and speed performance are not significant, e.g. where the motor is operated at a specific speed and load conditions are well defined. Problems with resonance can prohibit operation at most speeds. This type of mode requires the least amount of power from the drive power supply of any of the excitation modes. Dual phase full-step excitation is where the Stepper Motors are operated with two phases energized at-a-time. This mode provides excellent torque and speed performance with a minimum of resonance problems. Dual excitation, provides about 30 to 40 percent more torque than single excitation, but does require twice the power from the drive power supply.
Stepper Motors - Half-Step
Stepper Motors have half-step excitation which is substitute single and dual phase operation resulting in steps 1 half the normal step size. This mode provides twice the resolution. While the motor torque output varies on substitute steps, this is more than offset by the need to step through only half the angle. This mode has become the predominately used mode by Anaheim Automation because it provides almost total freedom from resonance problems. Stepper Motors can be operated over a vast range of speeds and used to drive almost any load frequently encountered.
Stepper Motors - Micro-Step
In Stepper Motors micro-step mode, a Stepper Motor's natural step angle can be divided into much smaller angles. For example, a basic 1.8 degree motor has 200 steps/revolution. If the motor is micro-stepped with a 'divide-by-10', then each micro-step would move the motor 0.18 degrees and there would be 2,000 steps/revolution. Commonly, micro-step modes range from divide-by-10 to divide-by-256 (51,200 steps/rev for a 1.8 degree motor). The micro-steps are produced by proportioning the current in the two windings according to sine and cosine functions. This mode is only used where even motion or more resolution is required.
Stepper Motors Feedback
Stepper Motors are commonly controlled by a driver and indexer. The amount, speed, and direction of rotation of Stepper Motors are determined by the appropriate configuration of digital control tools. The central types of control tools for Stepper Motors are: Stepper Motors Drivers, Stepper Motors Control Links, and Stepper Motors Controllers. These tools are set up in figure 8. The Stepper Driver accepts the clock pulses and direction signals and translates these signals into appropriate phase currents for the Stepper Motor. The Stepper Indexer creates the clock pulses and the direction signals for the Stepper Motors. The computer or PLC (Programmable Logic Controller) sends out commands to the indexer.
Stepper Motors Accessories
Along with step motors, Anaheim Automation carries an extensive line of drivers and controllers, power supplies, gear motors, gearboxes, step motors linear actuators and integrated step motors/driver packages. Additionally, Anaheim Automation provides encoders, brakes, HMI couplings, cables and connectors, linear guides and X-Y tables. If the step motors is not ideal for your application, you might also consider BLDC, brush DC, servo, or AC motors, and their compatible drivers/controllers.
Stepper Motors Basic Types
Each type of stepper motors varies per application by its construction and functionality. The 3 most frequent stepper motors types are Variable Reluctance, Permanent Magnet, and Hybrid Stepper Motors.
Variable Reluctance (VR) Stepper Motors
VR stepper motorss are characterized as having multiple soft iron rotors and a wound stator. VR stepper motors commonly operate on the fundamental principle of the magnetic flux finding the lowest reluctance pathway through a magnetic circuit. In general operation, VR stepper motorss have relatively elevated step rates of 5 to 15 degrees and have no detent torque. The step angles taken in VR stepper motors are related to the number of teeth the stator and rotor have. The equation relating these two variables can be found in the formula section of this guide.
How Does a Variable Reluctance Stepper Motors Work?
Referring to Figure 1 on Page 2, the poles become magnetized when the stator windings are energized with DC current. With the poles becoming magnetized, the rotor teeth are now attracted to the energized stator poles and rotate to line up. With the windings around stator A becoming energized the rotor teeth become attracted allowing the poles to line up. When A’s windings become de-energized and B’s windings become energized, the rotor rotates to line its teeth with the stator teeth. This process continues in sequence with C, followed by D being energized allowing for the rotor to rotate.
Brief Summary of Variable Reluctance Stepper Motors:
• The rotor has multiple soft iron rotors with a wound stato
• Least elaborate and expensive stepper motors
• Big step angles
• No detent torque detected in hand rotation of a de-energized motor shaft
Permanent Magnet (PM) Stepper Motors
PM stepper motorss are composed of permanent magnet rotors with no teeth, which are magnetized perpendicular to the axis of rotation. By energizing the 4 phases in sequence, the rotor rotates due to the attraction of magnetic poles. The stepper motors shown in Figure 2 on page 3 will take 90 degree steps as the windings are energized in clockwise sequence: ABAB. PM stepper motorss commonly have step angles of 45 or 90 degrees and step at relatively low rates. However, they exhibit elevated torque and excellent damping characteristics. Anaheim Automation carries an extensive selection of PM stepper motorss, ranging from 15 to 57mm in diameter.
Brief Summary of Permanent Magnet (PM) Stepper Motors:
• The rotor is a permanent magne
• Big to moderate step angle
• Often utilized in computer printers as a paper feeder
Hybrid Stepper Motors
Hybrid stepper motors incorporate the qualities of both the VR and PM stepper motors designs. With the Hybrid stepper motors’s multi-toothed rotor resemblance of the VR, and an axially magnetized concentric magnet around its shaft, the Hybrid stepper motors provides an increase in detent, holding and dynamic torque. In comparison to the PM stepper motors, the Hybrid stepper motors provides performance enhancement with respect to step resolution, torque, and speed. In addition, the Hybrid stepper motors is capable of operating at elevated stepping speeds. Typical Hybrid stepper motorss are built with step angles of 0.9°, 1.8°, 3.6° and 4.5°; 1.8° being the most frequent step angle. Hybrid stepper motors are ideally suited for applications having stable loads with speeds under 1,000 rpm. There are key components which are influential of the running torque of a Hybrid stepper motors which are laminations, teeth and magnetic materials. Increasing the amount of laminations on the rotor, accuracy and sharpness of the rotor and stator teeth, and strength of magnetic material are all factors taken into account in providing optimal torque output for Hybrid stepper motors.
Brief Summary of Hybrid Stepper Motors:
• Smaller step angles in comparison to VR and PM stepper motors
• Rotor is made of a permanent magnet with fine teeth
• Increase in detent, holding and dynamic torque
&bull 1.°° is the most frequent step angle
NOTE: At Anaheim Automation, the 1.8 degree Hybrid stepper motors is the most amplely stocked stepper motors type, ranging in NEMA frame sizes, 08 to 42. The Hybrid stepper motors can also be driven two phases at a time to yield greater torque, or alternately one then two then one phase, to produce half-steps or 0.9 degree increments.
Application Note - "Musical Motors" - Stepper Motors and Their Virtuoso Performance!
Anaheim Automation's amazing versatility of control systems is evident in their fresh program titled, Musical Motors. They have utilized stepper motors, stepper drivers, and stepper controllers to operate at speeds that coincide with musical notes and pitches to produce a variety of distinct tunes. Each tune is performed by simply running the program that converts each music note into a certain step-per-second. All of the distinct stepper motors are programmed to produce an appropriate pitch constructed on how many steps-per-second they run, and for how long. Frequently played at a trade show, the program provides the element of surprise; many people do not expect to hear music that is being played by stepper motors!
Tech Tip - AC Motors Advantages and Disadvantages
The most customary and basic industrial motor is the 3-phase AC induction motor, sometimes shortened to AC Motor. Pertinent detailed information can be found about AC motors by checking the nameplate.
Advantages of Using AC Motors
• AC Motors are of a basic design
• The basic design AC motors: Simply stated, a series of 3 windings in the exterior stator section with a basic rotating section (rotor). The changing field caused by the 50 or 60 Hertz AC line voltage causes the AC motor rotor to rotate around the axis of the motor.
• The speed of AC motors will depend upon these 3 variables:
1. The fixed number of winding sets (poles) built into AC motors, which determines the motor's base speed.
2. The frequency of the AC line voltage. Variable speed drives change this frequency to change the speed of AC motors.
3. The amount of torque loading on AC motors, causes slipping.
• AC Motors are of a low cost construction
AC motors have the advantage of being the lowest cost motor. AC motors are perfect for applications requiring more than about 1/2 hp (325 watts) of power. This is due to the basic design of AC motors. For this reason, AC motors are commonly chosen for fixed-speed applications, such as in industrial applications and for commercial and domestic applications where AC line power can be easily attached. Over 90% of all motors are AC induction motors. They are found in air conditioners, washers, dryers, industrial machinery, fans, blowers, vacuum cleaners, and several other applications.
• AC Motors operate reliably
The basic design and construction of AC motors casue them to be intensely certain and are thought to be low maintenance. Unlike DC Brush Motors, there are no brushes to replace. If AC Motors are used in the applicable environment, protected by an enclosure, AC motors can expect to replace the bearings after several years of continuous operation. If the application is well designed in a guarding environment, AC motors may not require the bearings to be replaced for more than 10 years.
• Easily Found Replacements
The extensive use of AC motors in several contrasting industries has resulted in easily found replacements for existing equipment repairs and/or upgrades. Several manufacturers adhere to either European (metric) or American (NEMA) standards.
• AC Motors are made by several manufacturers , so it is relatively easy to obtain replacements (for basically the same motor)
• AC Motors are designed in a variety of mounting styles (dependent upon the motor manufacturer). Foot Mount, C-Face, Large Flange, Vertical and Specialty.
• There are several environmental styles available for AC Motors, to include a all-inclusive range of applications and industries, called Specialty AC Motors by most. Because of the all-inclusive range of environments in which people want to use AC motors, manufacturers have adapted by providing a all-inclusive range of packaging/enclosure designs, such as Open Drip Proof (ODP), Completely Enclosed/Fan-Cooled (TEFC), Completely Enclosed/Air-Over (TEAO), Completely Enclosed/Blower-Cooled (TEBC), Completely Enclosed/Non-Ventilated (TENV), and Completely Enclosed/Water-Cooled (TEWC) versions.
Disadvantages of Using AC Motors
• High-priced speed control - Speed controllers can be high-priced. The electronics required to handle an AC inverter driver are considerably more high-priced than those required to handle a DC motor. However, if performance requirements can be met ~meaning that the required speed range is over 1/3rd of base speed ~ AC inverters and AC motors are usually more cost-effective overall, than are DC motors and DC drives. This is especially valid for applications larger than 10 horsepower, because of cost savings in the AC motor.
• Inability to operate at low speeds - Standard AC motors should not be operated at speeds less than about 1/3rd of the base speed, due to thermal considerations. A DC motor should be thought to be for these applications.
• Exhaused positioning control - Positioning drivers and controllers can be high-priced and crude. Even a vector drive is exceptionally crude when controlling a standard AC motor. Stepper motors and Servo Motors are more applicable for applications wherein positioning and speed control is crucial.
Stepper Motors Lifetime
The average lifetime for stepper motors is 10,000 operating hours. This approximates to 4.8 years; given the stepper motors operates 1 eight-hour shift per day. The lifetime of stepper motors may vary in regards to how rigorous the stepper motors are run and the users application.
Stepper Motors Windings Configuration
Stepper motors are wound on the stator poles in either a bifilar or unifilar configuration. The term unifilar winding refers to the winding configuration of the stepper motors where each stator pole has 1 set of windings; the stepper motors has only 4 lead wires. This winding configuration can only be driven from a bipolar driver. The term bifilar winding refers to the winding configuration of stepper motors where each stator pole has two of identical windings; the stepper motors will have either six or eight lead wires, depending on termination. This type of winding configuration will simplify operation in that transferring current from 1 coil to another, wound in the opposite direction, will reverse the rotation of the motor shaft. Unlike the unifilar winding which will only work with a bipolar driver, the bifilar winding configuration can be driven by a bipolar or unipolar driver.
Stepper Motors Physical Properties
The essential components used in stepper motors are the shaft, rotor and stator laminations, bearings, magnets, copper wires and lead wires, washers, and front and end covers. Most shafts of stepper motors are made of stainless steel, while the stator and the rotor laminations are made up of silicon steel. The silicon steel allows for higher electrical resistance which lowers core loss. The distinct magnets available in stepper motors allow for diverse construction considerations. These magnets are made of ferrite plastic, ferrite sintered and Nd-Fe-B bonded magnets. The bearings of stepper motors depend on size of the motor. The housing materials are composed of distinct other metals like aluminum, which allow for high resistance to heat.
Stepper Motors Customization
We provide a variety of options to customize Stepper Motors. The list of modifications includes, but is not limited to: brake, shaft, oil seal for an IP65 rating, mounting dimensions, torque, voltage, and speed. Please give us a call for any custom applications using Stepper Motors.
How Do Stepper Motors Work
The main use of standard stepper motors is to control motion, whether it is linear or rotational. In the case of rotational motion, receiving digital pulses in a accurate sequence allows the shaft of a standard stepper motor to rotate in disconnected step increments. A pulse (also referred to as a clock or step signal) used in a standard stepper motor system can be produced by microprocessors, timing logic, a relay or toggle switch closure. A train of digital pulses translates into accurate shaft revolutions. Each revolution requires a given number of pulses and each pulse equals 1 rotary increment or step, which is only a portion of 1 full rotation. There are many relationships amongst the motors shaft rotation and input pulses. One such relationship is the direction of rotation and the sequence of adjusted pulses. With suitable sequential pulses being delivered to the instrument, the rotation of the shaft motor will undergo a clockwise or counterclockwise rotation. Another relation amongst the motors rotation and input pulses is the relationship between frequency and speed. Increasing the frequency of the input pulses also allows for the speed of the motor shaft rotation to increase.
Stepper Motors Advantages
Bipolar stepper motors vary in cost based on the criteria for each application. Some criteria include options of 0.9 deg;, 1.8 deg;, 3.6 deg; and 4.5 deg; step angles, torque ranging from 1 to 5,700 oz-in, and NEMA frame sizes of 08 to 42. Additional attachments such as cables and encoders can be purchased separately for an additional cost. With our friendly customer service and professional application assistance, Anaheim Automation often surpasses customer expectations for fulfilling specific bipolar stepper motors and driver requirements, as well as other motion control needs.
How are Stepper Motors Controlled
Standard stepper motors perform the conversion of logic pulses by sequencing power to the stepper motors windings; generally, one supplied pulse will yield one rotational step of the motor. This accuracy is provided by a stepper driver, which is able to control speed and positioning of the standard stepper motors. The stepper motors increment an exact amount with each control pulse, converting digital information into precise incremental rotation without the need for feedback devices, such as tachometers or encoders. Since the standar stepper motors/drivers is an open-loop system, the problems of feedback loop phase shift and resultant instability, common with servo motor/drive systems, are eliminated.
Eight-Lead Stepper Motors is the Best Option
Have you wondered why we carry the most stock in the eight-lead stepper motors configuration than the six or four lead configurations? Eight-lead stepper motors are wound like unipolar stepper motors, but the difference is that the leads are not connected (attached) to the common internally to the motor. The flexibility of the eight-lead stepper motors is in that it can be configured in several different ways:
• Bipolar with single winding per phase, which will run the stepper motors on half of the windings available, reducing the available low speed torque, and requires less current to operate.
• Bipolar with SERIES windings, which provides higher inductance, but lower current per winding
• Bipolar with PARALLEL windings, which requires a higher current, but outperforms because the winding inductance can be reduced.
The many configurations of the eight-lead stepper motors make it a logical choice for our to stock, as it is cost-effective to manufacture and serves a wide range of customers and stepper motors applications.
Electric Motor Types
Electric motors are frequently classified by motor type, i.e. Alternating Current (AC) versus Direct Current (DC). This distinction is not always so rigid, in that many classic DC motors run on AC power. This type of electric motor is often referred to as universal motors.
Most industries used the rated output power specification of the motor to categorize motor types. For example, those motor of less than 746 Watts are often referred to as fractional horsepower (FHP). Recently, the trend toward electronic control further muddles the electric motor distinctions, as modern motor drivers and controllers have moved the commutator out of the motor casing. For the latest type of motors, driver and controller circuits are relied upon to generate sinusoidal AC drive currents. Examples of such are: the Blushless DC Motor (BLDC) and the Stepper Motors, both being poly-phase AC motors requiring external electronic control. Although historically, stepper motors (such as for maritime and naval gyrocompass repeaters) were driven from DC switched by contacts.
Considering all rotating (or linear) electric motors require synchronism amidst a moving magnetic field and a moving current sheet for average torque production, there is a clearer distinction amidst an asynchronous and synchronous types. An asynchronous motor requires slip amidst the moving magnetic field and a winding set to induce current in the winding set by mutual inductance; the most ubiquitous example being the standard AC Induction Motor which must slip to generate torque. In the synchronous types, induction (or slip) is not a requisite for magnetic field or current production. See the chart below to help determine if a stepper motors, Brush or BLDC motor, AC or Servo is the appropriate motor choice for your application.
How to Select Stepper Drivers
The amount, speed, and direction of rotation of a standard stepper motor are determined by the applicable configurations of digital control devices. Selecting the most compatible stepper drivers, motors, and/or controllers, can save the user money and be a less burdensome motion control solution. We categorize the main types of digital control devices as follows:
• Stepper Drivers – offered in full-step, half-step and micro-step
•Standard Stepper Motor Controllers (sometimes referred to as Control Links – controllers indexers, and pulse generators sold separately or in drivers packs
• Standrard Stepper Motor Driver Packs – packaged units that include drivers and optional controller, with a matched power supply (some models are enclosed units that are fan-cooled)
• Integrated Stepper Drivers/Controllers – packaged at the end of a standard stepper motor are drivers and simple controllers (only available for high-torque stepper motors)
Stepper drivers provide a method to accurately control speed and positioning. With each pulse converted into digital data, the motor is able to undergo an exact incremental rotation without the need for feedback mechanisms i.e. tachometers or encoders. With an open-loop system, the problems of feedback loop phase shift and resultant instability, common with servo drives, are eliminated. Before a designer selects an apporpirate stepper drivers and motor combination for an application, there are certain variables needed to be considered. A designer must examine various parameters such as load characteristics, performance requirements, and mechanical design including coupling techniques for an optimal solution for a stepper drivers and motor combination. Failure to do so can result in poor system performance or cost more than necessary. For optimum stepper drivers motion control, the following factors should be taken into consideration:
a. Distance to be traversed
&nbps; b. Maximum time allowed for a traverse
&nsbp;c. Desired detent (static) accuracy
d. Desired dynamic accuracy (overshoot)
e. Time allowed for dynamic accuracy to return to static accuracy specification (settling time)
f. Required step resolution (combination of step size, gearing, and mechanical design)
g. System friction: All mechanical systems exhibit some frictional force. When sizing the motor, remember that the most must provide enough torque to overcome any system friction. A small amount of friction is desired since it can reduce settling time and improve performance overall
h. System inertia: An object’s inertia is a measure of its resistance to changes in velocity. The larger the inertial load, the longer it takes a motor to decelerate or accelerate the load. The speed at which the motor rotates is independent of inertia. For rotary motion, inertia is proportional to the mass of the object being moved times the square of its distance from the axis of rotation
i. Speed/Torque characteristics of the motor: Torque is the rotational (in ounce-inches) defined as a linear force (ounces) multiplied by a radius (inches). When selecting a stepper drivers and motor, the capacity of the motor should exceed the overall requirements of the load. The torque any motor can provide varies with its speed. Individual speed/torque curves should be consulted by the designed for each application
j. Torque-to-Inertia Ratio: This value is defined as a motor’s rated torque divided by the rotor’s inertia. This ration (measurement) determines how quickly a motor can accelerate and decelerate its own mass. Motors with comparable torque ratings can have different torque-to-inertia ratios as a result of varying construction
k. Torque margin: Whenever possible, stepper drivers which can provide more torque than is needed should be specified. This torque margin allows for mechanical wear, lubricant hardening, and other unexpected friction. Resonance effects can cause the motor’s torque to be slightly lower at some speeds. Selecting stepper drivers and motors system that provides at least 50% margin above the minimum required torque is ideal. More than 100% can prove too costly
2. Calculation: Measurement of inertia, friction and workloads reflected to motor.
a. In an open-loop stepper drivers system, the motor does not “know” if excessive inertia or friction has made the motor lose or gain one or more steps, thus affecting the position accuracy
b. Load inertia should be restricted to no more than four times motor rotor inertia for high performance (relatively quick) systems. A low performance system can deliver step accuracy with very high inertia loads, sometimes up to ten times rotor inertia. System friction may enhance performance with high inertia loads
Experimentation for motor sizing is crucial due to dynamic changes in system friction and inertia, (load anomalies) which are difficult to calculate. Motor resonance effects can also change when the motor is couple to its load
Stepper Motors Accuracy and Resolution
Standard Stepper motors are a component used in functions pertaining to open loop positioning and velocity. Fundamentally, the system's accuracy depends on the standard stepper motors and the drive's precision and behavior, because there is not feed-back transducer.
Microstepping, accurate sine/cosine current references, and second order damping have allowed the stepper motors to become the ideal candidate for applications dealing with precision control. Disregarding the drive, the standard stepper motors has distinct qualities that must be considered in regard s to accuracy in any application.
Standard Stepper motors are assembled to a certain tolerance. Usually, a stepper motors has a tolerance of +/- 3% non accumulative error regarding any step's location. In other words, on a typical 200 step per revolution stepper motors, teach step will be within 0.18-degree error range. The standard stepper motors can essentially resolve 2000 radial locations, accurately. Incidentally, this is the 10 microstep drive's resolution.
Beyond the resolution of 10, i.e. 125, there is no real additional precision(there may be more smoothness, but no increase in accuracy). Similarly, a voltmeter that displays 6 digits while having 1% accuracy only contains significant information in the first two digits. Two exceptions allow for higher resolutions: standard stepper motors that run in a closed-loop application with a high-resolution encoder, or an application that needs to operate smoothly at extremely low speeds (fewer than 5 full steps per second).
Motor linearity is another factor that affects precision. Motor linearity is how the standard stepper motors operates between step locations. For every step pulse sent to a 10 microstep drive, a typical 1.8 per step motor should move precisely 0.18 degrees. Most stepper motors faces non-linearity; microsteps refuse to evenly spread themselves over a full step, and instead bunch together. Commonly two effects may occur: deceleration where the microsteps bunch up and cyclic acceleration where the microsteps spread apart cause dynamically low speed resonances. Statically, the stepper motors position is not ideal.
Stepper Linear Actuators Setup
Manual Linear Actuators may have a crank or control knob as well as a lead screw which is extremely common in most applications. The knob of Linear Actuators can also be indexed to display the angular position of the load. The displacement of Linear Actuators is associated with the angular displacement of the knob by the lead screw pitch. Precision Linear Actuators do not employ a lead screw, but rather Linear Actuators of that caliber use a fine-pitch screw which depresses a hard metal pad on the platform of the storage. Rotating the screw will move the platform in a linear motion. A spring is used to maintain force between the platform and Linear Actuators. This allows for a more precise motion for Linear Actuators. Linear Actuators mounted vertically use something different. The actuator is affixed to the moveable platform and its tip rests on a metal pad on the fixed base. The weight of the platform and its load is borne by the actuator.
In many Linear Actuators, a stepper motor may be utilized in place of a manual knob. A stepper motor used in Linear Actuators can move in fixed increments reliant upon the step resolution of the system. The Linear Actuators, in this case, move similarly to an indexed knob.
In many Linear Actuators, a DC motor may be used instead of a manual knob control. A DC motor, however, will not move in specific increments, in the way stepper motors or knobs in Linear Actuators would. This necessitates an alternative means for Linear Actuators for position verification. This can be dealt with by an encoder being integrated into Linear Actuators. The encoder permits a motion controller to reliably move the stage to set positions within the Linear Actuators.
Stepper Motors Basics
A stepper Motor is a digital apparatus. Digital information is processed by the Stepper Motors to achieve an end result. In this case, controlled motion. One might conclude that Stepper Motors will reliably follow digital commands just as a computer is supposed to. This is the classifying attribute of Stepper motors.
Stepper Motors are an electrical motor that are driven by digital pulses instead of a constantly applied voltage. Intrinsic in this concept is open-loop control, in which a train of pulses are converted into so many shaft revolutions, with each revolution requiring a given number of pulses. Each pulse is equal to one rotary increment, or step (hence, Stepper motors), which is only a fraction of one complete rotation.
For that reason, counting pulses can be utilized in Stepper Motors to meet a needed amount of shaft rotation. The count automatically represents how much movement has been achieved, without the need for feedback info, as with servo systems.
Stepper Motors General Safety Considerations
The following safety considerations are MUST be observed during all stages of operation, service and repair. Failure to abide by these safety precautions violates safety standards of design, production, and designated use of Stepper Motors, drivers and controllers. Motion Marketplace assumes no responsibility whatsoever for the customer's inability to comply with these constraints. Even high-quality products, when operated or installed incorrectly, can be hazardous. Safety measures are required to be observed by the user with regard to the load and operating environment. The customer is solely liable for proper selection, installation and operation of the products purchased from our company.
• Use caution when handling, during trials, and adjusting during installation, set-up and operation.
• Service MUST NEVER be performed while power is applied.
• Be sure the motor/driver has plenty of heat dissipation and air flow
• Exposed circuitry should be properly protected or enclosed to limit unauthorized human contact with live circuitry.
• All products should be solidly mounted and effectively grounded.
• Hazardous elements such as flammable gases, vapors, liquids or dust should not interact with motors while they are in operation.
NOTE: Please Use a RMA Form should you need to return a product for REPAIR. This form can be found in Support, Forms, RMA Request on this web site.
Tech Tip - Harnessing the Benefits of Open Loop Systems
In open-loop systems, step motors can offer accurate, stable speed and positioning that can match the best servo performance if properly installed. The simplicity of their design allows them to operate without tachometers, encoders, or other drawbacks that increase the cost of operation. Appropriate installation makes it easy to pinpoint the precise effect of the operation, since they increment a exact amount with each control pulse. Moreover, the rate of control pulses decides motor speed so that it, too, is entirely predictable. Thus, in the right mechanical environment, stepper motor systems can provide whatever degree of accuracy and reliability an application requires.
Designing a System:
Stepper motors offer multiple usage benefits over servos, the first of which being cost. In nearly any application, stepper motors can be implemented at a fraction of the price of servo. A common problem with servo drives is feedback loop phase shift and instability. Nevertheless, stepper motors are open-loop systems that entirely void any potential problem that could arise in this area.
The initial design phase for open-loop systems can be likened to that of the servo system. Load characteristics, performance requirements, and mechanical design, including coupling techniques, must be taken into account before a designer can properly select the most appropriate stepper motor and driver combination for the application.
After these factors have been verified, the motor specifications and system motion controller, such as a computer or PLC, can be established. Then the design comes down to selecting the best fitting driver and controller to produce the motion needed for the application.
Defining a Driver Pack:
In order to obtain an ideal solution, the following factors have to be considered:
1. Start with the stepper motor(s) and controller you have selected for your application.
2. Use one driver for each motor. The driver needs to match the motor current (amps per phase).
3. Incorporate a power supply that supports the driver(s) and motor(s).
4. Select an interface to handle communications between the control mechanism and the indexer (parallel, RS422, RS232C, serial, PLC, or manual switches).
5. Configure the Driver Pack with items 2 through 4 as applicable, or see Driver Packs on our website.
NOTE: When the wiring from a driver to a stepper motor goes beyond 25 feet, consult us for further assistance. Shielded motor cable can be purchased separately.
Application Note: 15- Axis Wind Tunnel Project
One of our customers offers services and products for the automobile industry, such as process automation, prototyping, engine test standards, and gauging appliances. Our customer happened to encounter a problem; trendy cars were being remodeled, and they required the control of stepper motors for their project. They had tried multiple other motion control companies before deciding to have us help them with their project. The project involved the cooling of an engine in a strange area. Our assignment was to create a prototype that would scoop air from beneath the car and redirect maximum air flow to this area.
It was nearly impossible to predict a precise shape which would allow maximum airflow, due to the fact that in order to fit into the available space, the duct needed to be in a highly complicated configuration. The solution involved constructing a flexible duct that could be reshaped by moving its parts. The duct was mounted in a wind tunnel and installed into the prototype of the car. Engineers then experimented with the duct's shape until they realized what shape provided the best air flow. This shape became the basic model to use in the overall prototype.
We needed to shape the duct without diverting from the project goal, and accordingly needed 15 axes of motion and one simple-to-use controller. To meet this necessity, we built five triple-axis stepper motor drivers, programmable indexers, an interface, and the required power supply into a compact package, along with 15 compatible stepper motors.
When the computer was booted up, the program came up, so the system didn't need any knowledge of the computer operation. Additionally, it reduced operation to answering three questions (prompting the user). The user could alter the speed at any time. The operator, however, did not need to know anything about base speed, acceleration, or deceleration, because the parameters for optimal motor speed was already preloaded with the system program. While operating, the program prompted the operator with, "What axis, how many steps, and which direction?" The user only had to press the F1 key to produce the desired motion for the stepper motors to move.
Thusly, the engineers were able to manipulate the air duct in order to achieve maximum air flow underneath the vehicle. The necessary motion was easily created at the press of a button, and the positions could be easily repeated. Finally, our customer's engineering staff was able to establish the precise shape of the duct that provided the car with maximum air flow. Simple, cost-efficient, and extremely effective stepper motors and drivers offered the solution the customer required.
Application Note - Stepper Motors
Stepper Motors are currently employed worldwide for various types of applications. These motors are offered as constant power devices. At low rpm's, a high torque can be attained. The same cannot be said at higher speeds. A high torque cannot be achieved at higher rpm's. These motors are excellent for positioning objects, such as conveyor belts, assembly lines, lathes, laser cutting, grinding and drilling machines, etc.
Stepper motors are perfect for precise positioning. You might have a fixed speed, variable speed, and position control. These motors are capable of handling complex positions or movements. These devices provide power and precision in a compact sizes. These motors can bear a great load. An excellent example to show this would be an escalator. Escalators are continuously working, and carry very heavy loads throughout the day. The stepper motor must to be able to take up to several hundreds of pounds, or perhaps even thousands. The speed of the escalator is consistent, and never changes no matter how many people are on it.
Another type of application could be an assembly line. This generally requires precise quick and place movements. Nearly all stepper motors are an open loop system, meaning there is no feedback info needed about the position. By tracking the input step pulses, the position is known.
A few of the advantages of a stepper motor include, but are not limited to:
• Its input pulse is proportionate to angle rotation
• If windings are energized at stand sill the motor has complete torque
• Differing rotation speeds are available, since the frequency of input pulses are proportionate to the speed.
• It is less expensive to have open-loop control that responds to digital input pulses
• Accurate response time to starting, stopping, and reversing
• Lack of brushes within the motor make it more reliable.
There are three seperate types of stepper motors to choose from: the variable -reluctance, the permanent-magnet, and last but not least the hybrid step motor. All three have different qualities for certain applications. Stepper motors have been around for quire some time, and are currently and will continue to be used throughout the world. No matter the application, the step motor will always rise to the occasion.
Application Note - Industries That Use Stepper Motors in Their Design
Stepper motors are versatile motion control components applicable to several industries, from entertainment and film, to the business world, to science and medicine.
Aircraft: Stepper motors are often used in aircraft instruments, scanning equipment, and sensing devices, such as antennas.
Automotive: SUV's and RV's, along with some high-end automobiles, use stepper motors to receive telecommunication signals. Stepper motors are also used for cruise control, automated dashboards gauges and electronic window equipment, in addition to being used in automobile factories on their production lines.
Cameras - Filming and Projection: Not only do stepper motors operate filming cameras and projectors, in the entertainment industry, but automated digital cameras and mobile phone camera modules utilize tiny stepper motors for focusing and zooming functions as well. The surveillance industry also uses stepper motors for zooming, tilting and scanning operations in surveillance and security cameras.
Entertainment and Gaming: Slot machines, lottery machines, raffles, card shufflers, and wheel spinners can all be operated by cost-efficient and reliable stepper motors. You can find stepper motors in stage productions to control curtains and lighting functions, for plays and concerts, as well as seminars and rallies.
Laboratory and Factory Improvements and Upgrades: Stepper motors are used to perform tenuous movements pertaining to mixing chemicals in laboratories, and operating equipment for controlled environmental testing. Stepper motors are employed in retrofit kits (stepper motors, drivers, controllers and power supplies) for CNC machine control, factory automation and assembly processes. Stepper motors can be found in scientific study, used to position observatory telescopes, and in many different types of scientific equipment, i.e. spectrographs, analyzers, and diagnostic machines, as well.
Medical: Stepper motors offer a wide variety of functions for the medical and dental world. Stepper motors are employed in medical scanners, multi-axis stepper motor microscopic or nanoscopic motion control of automated devices, auto-injectors, samplers, dispensing pumps, respirators, blood analysis machinery and chromatographs. In the dental industry, stepper motors operate fluid pumps, and are frequently found inside digital dental photography equipment.
Office Equipment: PC-based scanning equipment, optical disk drive head driving mechanisms, bar-code printers, label and box printers, scanners, and data storage drives all employ stepper motors for their motion control operation.
Stepper Motors Environmental Considerations
The environmental and safety considerations listed here must always be observed during all phases of operation, service and repair of stepper motors system. Failing to act in accordance with these precautions violates safety standards of design, manufacture and intended use of the stepper motors, driver and controller. Please note: even with a well?built stepper motors, products operated and installed improperly can be hazardous. Precautions must be taken by the user with respect to the load and operating environment. The customer is fundamentally responsible for the correct selection, installation, and operation of the stepper motors system.
The enviroment in which stepper motors are used must be conducive to good general practices of electrical/electronic equipment. Never operate the stepper motors in the presence of flammable gases, dust, oil, vapor or moisture. For outdoor use, the stepper motors, driver and controller must be shielded from the elements by an acceptable cover, while still providing acceptable air flow and cooling. Moisture can cause an electrical shock hazard and/or induce system breakdown. Adequate consideration should be given to the avoidance of liquids and vapors of any kind. Notify the factory should your application require specific IP ratings. It is smart to install the stepper motors, driver and controller in an environment which is free from condensation, dust, electrical noise, vibration and shock.
Additionally, it is preferred to work with the stepper motors/driver /controller system in a non?static, secure environment. Exposed circuitry should always be correctly guarded and/or enclosed to prevent unauthorized human contact with live circuitry. Do not perform work while power is applied. Don’t plug in or unplug the connectors when power is ON. Wait for at least 5 minutes before inspecting the stepper motors system after turning power OFF, because even after the power is turned off, some electrical energy will be remaining in the capacitors of the internal circuit of the stepper motors driver.
Plan to install the stepper motors, driver and/or controller in a system design that is free from debris, such as metal debris from cutting, drilling, tapping, and welding, or any other foreign material that could come in contact with circuitry. Failing to prevent debris from entering the stepper motors system can cause harm and/or shock.
How to Select Stepper Motors
There are several crucial criteria involved in selecting the proper stepper motors:
1. Desired Mechanical Motion
2. Speed Required
4. Stepper Mode
5. Winding Configuration
With fitting logic pulses, stepper motorss can be bi-directional, synchronous, afford rapid acceleration, run/stop, reversal, and can interface easily with other digital mechanisms. Characterized as having low-rotor moment of inertia, no drift, and a noncumulative positioning error, a stepper motors is a price-effective solution for quite a few motion control applications. In general, stepper motors operate without feedback in an open-loop fashion and occasionally match the performance of more expensive DC Servo Systems. As mentioned previously, the only uncertainty associated with a stepper motors are a noncumulative positioning error measured in % of step angle. Frequently, stepper motors are manufactured within a 3-5% step accuracy.
Motion constraints, load characteristics, coupling techniques, and electrical constraints need to be understood before the system designer can select the best stepper motors/driver/controller combination for a specific application. While not a hard task, several key factors need to be considered when determining an optimal stepper motors solution. The system designer should adjust the characteristics of the elements under his/her control, to meet the application constraints. Our company offers many options in its broad line of stepper motors products, allowing for the maximum amount of design flexibility. Though it may seem overwhelming to choose, the result of having a large number of options is a high-performance system that is cost-effective. Elements necessary to consider include the stepper motors, driver, and power supply selections, as well as the mechanical transmission, such as gearing or load weight reduction through the use of alternative materials. A few of these relationships and system parameters are described in this guide.
Inertia is the measure of an object’s resistance to change in velocity. The larger an object’s inertia, the greater the torque required to accelerate or decelerate it. Inertia is a property of an object’s mass and shape. A system designer might wish to select an alternate shape or low-density material for optimal performance. If a limited amount of torque is accessible in a selected system, then the acceleration and deceleration times will increase. For efficient stepper motor systems, the coupling ratio (gear ratio) should be selected so the reflected inertia of the load is equal to, or greater than, the rotor inertia of the stepper motors. It is highly recommended that this ratio not be less than 10 times the rotor inertia. The system design might require the inertia to be added or subtracted by selecting different materials or shapes of the loads.
NOTE: The reflected inertia is reduced by a square of the gear ratio, and the speed is boosted by a multiple of the gear ratio.
Every mechanical system exhibits some frictional force. The designer of a stepper motor system has to be able to predict elements causing friction within the system. These elements could be in the form of bearing drag, sliding friction, system wear, or the viscosity of an oil filled gear box (temperature reliant). A stepper motor must be selected that can overcome any system friction and still supply the necessary torque to accelerate the inertial load.
NOTE: Some friction is desirable, since it can reduce settling time and improve performance.
The positioning resolution necessary for the application may have an effect on the type of transmission used, and/or selection of the stepper motors driver. For instance: A lead screw with 5 threads per inch on a full-step drive supplys 0.001 inch/step; half-step supplys 0.0005 inch/step; a microstep resolution of 25,400 steps/rev supplys 0.0000015 inch/step.
What temperatures are stepper motors able to run at?
Most stepper motors are made with Class B insulation. This allows the stepper motor internal wiring to sustain temperatures of up to 130Â° C. With an ambient temperature of 40Â° C, the stepper motor has a temperature rise allowance of 90Â° Celcius. Stepper motors can run continuously at these temperatures.
What is the difference between a Unipolar and a Bipolar stepper motor?
The main difference between unipolar and bipolar stepper motor is the center tap connections. A unipolar motor is wound with six lead wires, each of these having a center tap. These would be used in applications needing high torque with high speed. Whereas a bipolar stepper motor has four lead wires but has no center tap connections. Bipolar stepper motors are used when you require high torque at low speeds.
When should I use microstepping?
microstepping is used in applications requiring the motor to operate at less than 700 PPS. At low pulse rates, stepper motors to less smooth and often vibrate.
What is a unipolar stepper motor?
A unipolar stepper motor is one of the two basic types of two phase stepper motors. The unipolar motor has one winding with a center tap per phase. Typically the center tap is made common, giving three leads per phase and six leads for the typical two phase motor. Mostly these two phase commons are internally joined making the motor have five leads. A micro controller or stepper controller can be used to control drive transistors in the right order, creating an ease of operation making the unipolar stepper motor the cheapest way to gain precise angular movements.
What is a bipolar stepper motor?
A bipolar stepper motor is a type of two phase stepper motor that has a single winding per phase. The current in t5he winding of this type of motor needs to be reversed in order to reverse a magnetic pole, thus making the drive control on bipolar stepper motors much more complicated. The winding's of a bipolar motor are used much more efficiently that that of the unipolar motors, they are much more powerful than a unipolar motor of the same size.
What is a brushless DC motor?
A brushless DC motor also referred to as electronically commutated motors are a type of synchronous motor that is powered by a DC electric source by way of a integrated inverter. This inverter will produce an AC electric signal to drive the motor. Additional sensors will control the inverter output. Brushless motors are often referred to as stepper motors, however stepper motors are designed to be frequently stopped at predetermined intervals and angular positions.
What is a stepper motor?
Stepper motors are DC motors that turn in distinct steps. At every step the motor holds its position needless of power, thus eliminating the necessity for feedback positioning sensors, so long as the motor is properly sized and no steps have been skipped. The removal of feedback requirements and the digital nature of a stepper motor makes it simple to integrate into digital systems.
What is the maximum speed of a stepper motor?
Modern stepper motors can reach rotation speeds of up to 1500 RPM, taking into consideration that the motor torque curve decreases considerably with the increasing of the step frequency. If a screw of 4 mm is run at 1500 RPM, we obtain a displacement speed of 1500*4mm=6000mm/min or 6 m/min. Therefore, in practice, the stepper motors runs at max 600 RPM because the torque decrease above that values.
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