Combination of resistor and PWM electronic device to control speed of a permanent magnet DC motor

摘要

A motor speed control system 10 includes a permanent magnet direct current electric motor 12. A first switch 14 is in series with the motor. A circuit 15 is in series with the first switch 14. The circuit 15 includes a resistor 16 and a second, pulse width modulated controlled, switch 18 in parallel with the resistor 16. An electronic controller 20 is operatively associated with the first and second switches for electronically controlling the first and second switches independently and in combination to control current to the motor to operate the motor at various speeds.