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Stepping Motor Schedule - Bipolar PM
ModelStep Angle
Phase Voltage
Phase Current
Phase Resistance
Phase Inductance
Holding Torque
Rotor Inertia

Permanent magnet stepper motors differ from hybrid stepper motors in the way magnetic poles are applied to their rotors. Hybrid stepper motors have physical teeth cut onto their rotors that are then magnetized. Permanent magnet stepper motors have poles applied to a featureless cylinder of magnetic material.

This is a simpler method of construction, which reduces the cost of a permanent magnet stepper motor. It also reduces the number of poles on the rotor and hence reduces torque and resolution.


Permanent magnet stepper motors are suited to applications where cost needs to be minimized and the torque of a hybrid stepper motor isn't required. A permanent magnet stepper motor fitted to a gearbox can produce more torque than a hybrid stepper motor of equal cost - albeit only at low speeds. This set-up has the added benefit of magnifying the stepper motor's detent torque, allowing it to hold position without being constantly powered.

The ratio of the gearbox will give very high resolution however it's backlash will reduce accuracy. These factors remove any benefits of micro-stepping. A chopper drive is more advantageous in permanent magnet stepper motors than in hybrid stepper motors since it makes the most of their limited power.