>> Mechanical Engineering
Some industrial applications of stepper motors call for very high stepping rates under variable load (variable motor torque) conditions. Since the motor torque depends directly on the current in the phase windings (typically 5 A per phase), one method of obtaining a variable-torque drive is to use an adjustable resistor in the drive circuit. An alternative method is to use a chopper drive. Switching transistors, diodes, or thyristors are used in a chopper circuit to periodically bypass (chop) the current through a phase winding. The chopped current passes through a free-wheeling diode back to the power supply. The chopping interval and chopping frequency are adjustable. Discuss the advantages of chopper drives compared with the resistance drive method.