Application Note 828 Increasing the High Speed Torque of Bipolar Stepper Motors

To successfully follow a velocity profile, a motor and drive combination must generate enough torque to: accelerate the load inertia at the desired rates, and drive the load torque at the desired speeds. While the size of a bipolar stepper motor generally dictates the low speed torque, the ability of the drive electronics to force current through the windings of the motor dictates the high speed torque. This application note shows that increasing the slew rates of the winding currents in a bipolar stepper motor pushes the motor to deliver more torque at high speeds. Simple voltage drives, L/R drives, and chopper drives are explained. L/R drives and chopper drives achieve slew rates higher than those achieved by simple voltage drives. Finally, an example chopper drive is presented.