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Stepping Motor Schedule - Bipolar Hybrid
ModelFrame SizeStep Angle
Phase Voltage
Phase Current
Phase Resistance
Phase Inductance
Holding Torque
Rotor Inertia
Detent Torque

A stepper motor uses a permanently magnetised rotor and an stator formed from two electromagnetic coils. The coils can be energized in four configurations. Switching from one configuration to another causes the rotor to "step" and align its magnets with the energized coil. Cycling through the four configurations in a certain order will cause the rotor to steadily move in one direction.

"Hybrid" stepper motor construction combines the two methods of rotor manufacture: variable reluctance and permanent magnet. This combined approach gives a great density of poles than either predecessor, increasing both resolution and torque.


The resolution of a stepper motor can be increased via microstepping. Instead of switching from one position to the next, the voltage applied to the destination coil is gradually increased. This gives smooth motion at the expense of torque. Conversely, a chopper drive will apply a spike of voltage at the start of each step, this reduces the time needed for current to start flowing in the destination coil, allowing the rotor to align in time for the next step even at a high speed under heavy load.

Pull-in torque is the maximum load under which a motor will accelerate from rest to a given speed. Pull-out is the maximum torque that the stepper motor can apply at a given speed. If torque or speed exceeds this curve the motor will lose synchronism and begin to "miss steps".