I want to put a quot;dimmer switchquot; (like the kind you put instead of a light switch to control how much electricity the circuit gets) before an AC motor running on 120 volts. Basically, we needed a motor for a project and it has a switch already on it for 2 different speeds of 600rpm or 1200 rpm (It was from a rather large industrial fan). I need it to spin slower and i was wondering if it will damage the motor to give it less voltage with the variable switch, or if the motor will run at all.Thanks in advance
An industrial fan will be ok on the dimmer switch, as long as the dimmer is rated for that power. Check carefully to be sure that it is. This won't hurt the motor.
I don't know about this specific motor, but in general AC motor speed is a function of the number of poles and the frequency. Thus lowering the voltage, by itself will not reduce the speed although you may see it moving slower because of the load. In these circumstances you are effectively slowing it down by overloading it and it will heat up accordingly. DC motors are a different beast and you can control their speed by voltage. Further, a dimmer switch does not reduce the peak voltage. What it does is chops off part of the AC waveform. Fundamentally, although this approach may do what you want, it is not a proper solution and I would not let it run unattended for any length of time. Also, keep a fire extinguisher handy.
