Author Options:

can you control an AC motor's speed? Answered

i have a <1hp motor that i'm currently trying to turn into a homemade chopsaw. one of the problems i'm running into is that the motor is spinning too fast for the blade to handle.

The idea is that i would use a triac with the gate connected inline with a capacitor that was connected off of one of the ac mains line. the hope was that i could control how much of the waveform the triac chopped off by setting the capacitance of the capacitor to some level where about 3/4 of the way through the cycle it would stop triggering the triac cutting off the end of the wave.

is this a possible method of managing the speed of an ac motor or am i setting myself up for heartache and pain in the form of a dead motor?

UPDATE: i underestimated the max speed that the chop saw blades are capable of, there's a large enough margin of safety that i'm not worried about overspeeding at all, i will leave this question up because it was answered so concisely and maybe it will help someone else out on their journey. look forward to the chopsaw instructable!


If this motor is BRUSHED, you can phase control it, otherwise, no,

thankyou, i've been searching the web for a clear answer and the only thing i've found have been adds for devices that do it for you and a bunch of forums where people asked questions similar but didn't get any kind of reply.

whether it has brushes or not you wil be able to controlle the speed. perhaps you know that stuff that controles the dim and bright of lights in your home you can use that just tjek the current ratting

Good luck

Gear the motor output down until it is slow enough. pullies and belts should do this OK for a saw.

You can change an induction motors speed by changing the cycles of the AC current.

Cycles up RPM up Cycles down RPM down.