Hello all:I was wondering if there was a way to take an electric motor using alternating current ( AC ) and hook it up to a sort of speed controller. Some one told me speed controllers burn out AC motors; is that true?Also, is there a way to hook up a speed controller to an electric motor using direct current ( DC )?Examples:I want to put a speed controller to an windshield wiper motor.I want to put a speed controller on a ceiling fan (not a dimmer switch).Any help would be greatly appreciated. Thank you all in advance.Have a beautiful day.
Both of the motors you mentioned can be speed-controlled. The ceiling fan motor is a capacitor-run motor. This type of AC motor, as well as shaded pole motors, can be controlled by reducing the voltage to the motor with a stepped or variable transformer (variac) or by adding series capacitance (3 or 4 speed wall mount fan controls) or a phase-control (dimmer) circuit. These devices actually reduce the TORQUE of the motor, which will cause the attached fan to drag the speed down. If you run the motor with no load, the speed will not vary properly. The 'brush-type' DC motor speed can be controlled by varying the voltage to it also. This could be done with a simple variable resistor (rheostat) which is terribly inefficient, or by means of Pulse Width Modulation (PWM). PWM switches the full power supply voltage to the motor on and off rapidly, and as you increase the On time in relation to the Off time, the average power applied to the motor increases, along with the motor speed. Most battery powered variable-speed tools use this method. It is a bit complicated, but quite efficient.
To control single phase AC motor, use a variable voltage transformer ( auto-transformer ). To control DC motor, use a variable DC voltage power supply.
You need to get a light dimmer switch that is capable of controlling inductive lighting loads. Just connect this in series with the motor and it should give a reasonable level of control. Ensure that the dimmer switch has a large enough current rating for the motor.
