TruCount™ multi-turn, absolute encoders are available on select StepSERVO™ Integrated Motors. There are numerous benefits of using multi-turn, absolute encoders in motion control, but you need not spend a fortune to get them. Simplified pricing on TruCount™ encoders makes the decision to purchase easy because there is no premium cost adder for them compared to the same integrated motors with incremental encoders.
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We offer different incremental encoder options for our stepper motors. Encoders are used to provide feedback to the motor drive or controller and improve overall performance of the step motor system. The following provides a summary of those encoder options.
If you read our article Why Do Step Motors Get Hot? you may have wondered "What does this mean to me?” Step motor losses are important because the energy lost in the motor results in heat. Any motor has a thermal constant that can be used to compute how hot the motor will get for a given level of energy dissipation. Once the windings exceed 130°C, the insulation on the motor windings will melt and it’s game over.
Step motor motion is conceptually simple: Just rotate the stator field and the rotor will follow, so long as you don’t expect it to violate the laws of physics. An easy but unpleasant way to violate said laws is to ask for more acceleration than the motor can achieve. So how does one perform step motor trajectory calculations? As we learned in the post Dynamic Torque & Step Motor Sizing, maximum acceleration is determined by torque divided by inertia.
The first thing many new users ask about step motors is: "what's the difference between holding torque and pullout torque?". Which one matters to me (as Herb Tarlek might say)? If you apply a constant current to one winding of a step motor, torque is produced according to this formula:
In our post Step Motor Heating we looked at step motor losses over a wide range of speeds and power supply voltages. Now, we deepen our examination. Step motors waste power in two ways: copper losses that result from the electrical resistance of the stator coils and iron losses from magnetic hysteresis and eddy currents. In both cases, this lost power results in the motor heating.
In our post What Do NEMA Sizes Mean?, we examined the NEMA frame sizes in which step motors are made. Larger frame sizes produce more torque. But this is not a one dimensional process: within a given frame size, the motor length can vary and that also affects torque. Because step motors require expensive tooling in order to be produced economically, a fixed rotor length is chosen, as is the stator that surrounds it.
Though it's long been rumored that step motors are driven by tiny hamsters on wheels contained inside, I can assure you that this is not only untrue, but also promulgated by unscrupulous pneumatic actuator salesmen. So how does a step motor work? In reality, step motors operate by electromagnetism. Specifically, a permanent magnet rotor such as the one shown below is attracted to electromagnets that reside in the stator.
Step motors are categorized by frame size, such as "size 11" or "size 23". Ever wonder how that came to be or what it means? The National Electrical Manufacturers Association sets standards for many electrical products, including step motors. Generally speaking, "size 11" mean the mounting face of the motor is 1.1 inches square.
If you are new to step motors, you may be wondering how to mount one in your application. You’ll need to be concerned with three things: piloting the motor, fastening it to the mounting surface, and coupling the shaft to your load.