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  • Tech Spotlight: The STR2 Stepper Drive

    Nov
    19

    Even though it's the smallest stepper drive in our line up, the STR2 stepper drive has some very big shoes to fill. It is the successor to the venerable 2035 drives, which was our very first standard drive offering and is still in production after 23 years! Fortunately for the STR2 it has an arsenal of performance benefits that allow it to outshine it's older brother.

  • Can I Operate a Step Motor at Full Current all the Time?

    Oct
    29

    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.

  • 0.9 Degree Step Motors

    Oct
    29

    Most popular hybrid step motors have a "step angle" of 1.8 degrees. The 1.8 refers to the angular distance between full steps and is a bit of an anachronism. Most applications now employ microstepping to electronically divide the step size to as low as 51200 steps/revolution. Nonetheless, another class of hybrid motors exists that provide a full step size of 0.9 degrees.

  • How Can You Calculate Step Motor Trajectories?

    Oct
    28

    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.

  • How Does Holding Torque Differ From Pullout Torque?

    Oct
    28

    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:

    torque_eqn

  • Why Do Step Motors Get Hot?

    Oct
    28

    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.

  • Step Motor Heating

    Oct
    28

    In our last post, we showed that you can get more torque at higher speeds if you operate a motor at a higher voltage.  In the example below, the red curve, measured at 70 VDC, provides much better high speed torque than the orange (12V) curve.   So why not always use 70 volts?  Better still, why not apply 100 volts and really flatten out that curve?

  • What is Step Motor Stack Length?

    Oct
    28

    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.

  • How Does A Step Motor Work?

    Oct
    28

    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.

  • What do NEMA sizes mean?

    Oct
    28

    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.

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