Author Options:

Need help Answered

I have a small 1/4 HP electric motor that runs @1750 rpms  I tried to put a basic dimmer switch on it to help regulate the speed but it it still runs wide open. Should this work or what can I do?


You should need repairing and replacement service .It can be cause of fire accident .I think you should not take risk.
Do you have good knowledge of electric motor?

If it did not slow down with the dimmer then you most likely have an induction motor. You cannot control the speed of an induction motor with a dimmer circuit. At best the motor and dimmer will both overheat. At worst one or the other will fail and may catch fire. You can control the speed of induction motors electronically with a variable frequency drive, however even the cheapest of these is going to cost many hundreds of dollars. You need to either use belts or gears to get the rpm you need or get a motor of the right speed.

Yep I agree with biochemtronics you would need a 200 watt pure sine wave veritable frequency power inverter to vary the speed of a ¼ horse induction motor.

AC motors run at a speed that is tied to frequency, so you might use a silicon-sine-wave generator or otherwise a gearbox.


It depends on the type of motor to a large extent. A brushed AC motor will work with a dimmer type control - an induction motor won't, because it needs to see a different FREQUENCY to drive it, not a different voltage.

See if there is some sort of printing or identification plate on the motor to go look up the specs or datasheet. That size motor might be industrial/commercial sized and there are multi-phased motors. They are controlled differently by PWM and can be wired up differently for power.