MOTION SYSTEMS HANDBOOK
Stepper motors designed to withstand harsh washdown conditions, like the IP65-rated SureStep line from AutomationDirect, are completely protected from solids and dust ingress and from low pressure water jets from any direction. Waterproof white epoxy coating on the motor laminations and special bearings and seals help keep moisture out of the motor.
Stepper motors — an overview
Stepper motors are one of the many motor options used in motion control systems. They’re known for their accurate
positioning capabilities and delivering high torque at low speeds. A distinguishing feature is that a typical stepper motor operates on open-loop control as opposed to closed loop like many other motor types, including servomotors. One way to classify stepper motors is according to the number of steps they can be commanded to move. So a 1.8° step motor is capable of 200 steps per
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revolution (1.8 x 200 = 360° or one full revolution) in full-step mode. If operated in half-step mode, each step becomes 0.9° and the motor can then turn 400 steps/revolution. Another mode called microstepping subdivides the degrees per step even further, allowing for extremely precise movements. The two most common types of stepper motors are the permanent magnet (PM) and the variable reluctance (VR) type. Stepper motors operate in a fairly straightforward way. Traditional VR stepper motors have a large number of electromagnets arranged around a central gear-shaped piece of iron. 8 • 2019
When any individual electromagnet is energized, the geared iron tooth closest to that electromagnet will align with it. This makes them slightly offset from the next electromagnet so when it is turned on and the other switched off, the gear moves slightly to realign. This continues with the energizing and de-energizing of individual electromagnets, thus creating the individual steps of motion. Newer hybrid stepper motors combine the best features of both PM and VR types. Here, the rotor is multi-toothed like the variable reluctance motor and contains an axially magnetized concentric magnet motioncontroltips.com | designworldonline.com
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