I have some power tools that are 220 50/60 Hz (they are brush motors). I would like to use them on 110 (US power). I know I can just get a step up transformer (which is probably what I will do), or plug into a 220 outlet. However 220 outlets are not so common in the US. My question is what would happen if I try to power them on 110. Since they are designed for 220 I'm assuming the resistance would be double that of a 110 motor, so at 110 the current would be half. I believe that speed is proportional to voltage and torque is proportional to the square of the current so would it operate at half speed and 1/4 the torque? Or could it draw more current than designed for and burn up? If so why?

I have actually searched on this question, and mostly found info on induction motors and wiring them in series or parallel. Not my case, or that you can't do it and it will burn up the motor. But no explanation as to why it would burn up.

 

It is very unlikely to give you satisfactory results. Use a step up transformer or wire up a 220 outlet like I did for my table saw. Realize, though, that with the step up it will draw twice the current at 110.

 

The Brushed AC/DC , Universal motor is a series field motor, very high torque under load, off load, the motor will gradually increase rpm until the only current requirement is to maintain the current sufficient to keep the armature rotating.
IOW. the only result you should see on lower voltage is lower top RPM.

 

Thanks for the fast response, good to know it won't burn up as that made no sense to me. To follow up though, Is there anyway to rewire the motor to run on the lower voltage? Like an induction motor where you switch the windings from series to parallel?

 

You cannot convert it to shunt (parallel) field.
You cannot get higher RPM's, if that is what you mean.

 

Thanks, yes that was the question. Someone told me you could but again it did not make sense.

 

One cheap option is to build a voltage doubler circuit. That will give you about 320 volts no load, and about 200 volts under load. Two adequate diodes and two fair sized capacitors and because it is DC there will be plenty of torque even with a lower voltage.
BUT caution is required because now neither side of the resulting power is at "ground" voltage so both sides of the line are a shock hazard.

 

Thanks, yes that was the question. Someone told me you could but again it did not make sense.

Keep in mind that the series field motor will run up to an max rpm based on applied voltage and friction & load
IOW, a runaway condition.