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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?

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.

In the posts What Do NEMA Sizes Mean? and What is Step Motor Stack Length? we discussed factors affecting holding torque in step motors, such as frame size and stack length.  Holding torque is a measure of how much rotating force is required to force a stationary step motor shaft out of position.

In our last post, we explored the possibility of connecting a step motor to a small gas engine for use in recharging a 12 volt battery. The effort resulted in a computer model which we hoped to use to optimize the design without having to expend excessive time and effort on trial and error. Our first concern was whether the step motor had the optimal number of winding turns on the stator. Changing the winding of a step motor is a difficult experiment because of the complexity of reprogramming a winding machine and loading it with a different size wire.