Reversing an AC Motor

[Richard Wagner]

What do I need to know before I attempt to reverse direction of an AC motor that is NOT identified as being reversible?

Because the motor is designed for a specific vendor application (Shopsmith), the motor manufacturer will not provide technical data on the motor.

[Anthony Whitesell]

Switching the leads (H->N and N->H) on a 110VAC motor will not reverse the direction. The thread Motor Wiring Gurus, could you have a look? at http://www.sawmillcreek.org/showthread.php?t=73609 is discussing a reversable motor.

[Rod Sheridan]

Hi Richard, the issue of reversing a single phase induction motor is whether or not the starting winding connections are available to you.

If the start winding connections are available, reversing them will reverse the motor rotation.

I have no experience with a Shopsmith at all, however if you reverse the motor rotation, you have to be careful that there aren't any fasteners in the powertrain that could come loose on reverse rotation.

Regards, Rod.

[John-Paul Murphy]

contact shop smith. I had one of those machines many years ago and it seems like it may have had a reverse switch. If so you should be able to find it in the wiring diagram for the shop smith. You did not say this was for an actual shop smith machine and if you wanted to leave the motor reversed or if you were looking for the ability to forward and reverse. ?
Rod makes a good point on the possibility of powertrain issues

[Richard Wagner]

Thank you folks for the replies and especially for the safety warnings. Cautions/Warnings are always applicable and welcome!

Shopsmith has not made this info readily available.

The intended application requires that I be able to easily switch back and forth. The application is not in a Shopsmith configuration. I just have a motor that came from a Shopsmith Mark V. It was unnecessarily replaced as a result of advise that I should have better verified.

[John-Paul Murphy]

did you try their customer service
1/800/762-7555

[Randall Frey]

Out of curiosity, how many leads are coming out of this motor and how are they labeled X1 X2, 1,2 etc? Some motors have a wiring diagram on the inside of the motor lead cover plate or on the motor nameplate.

[Richard Wagner]

There is a ground wire (green) and a black and a white wire coming out of the motor. These are the standard 110 VAC connections.

If you dig into the motor you discover a nest of wires not intended to be accessed by the uninformed. Within that nest there are two black and two red wires along with a white and maybe gray wire.

I expected to find a green wire but did not. I cannot ascertain which wires go to the capacitor. Even an ohmmeter check leaves me in doubt.

I suspect the black wires are the start winding and the red wires are the run winding (maybe vice versa).

Theory says - reversing either the black wires or the red wires will reverse the motor direction. Without a wiring diagram - I am hesitant to try.

[Mike Henderson]

There is a ground wire (green) and a black and a white wire coming out of the motor. These are the standard 110 VAC connections.

If you dig into the motor you discover a nest of wires not intended to be accessed by the uninformed. Within that nest there are two black and two red wires along with a white and maybe gray wire.

I expected to find a green wire but did not. I cannot ascertain which wires go to the capacitor. Even an ohmmeter check leaves me in doubt.

I suspect the black wires are the start winding and the red wires are the run winding (maybe vice versa).

Theory says - reversing either the black wires or the red wires will reverse the motor direction. Without a wiring diagram - I am hesitant to try.

As long as you don't create a dead short across the input lines, you probably won't do any serious damage to the motor. Try switching (reversing) what you think is the starting coil (actually you can reverse either coil) and check across the line to see that you're not a dead short. Then just touch the plug to the outlet and see what happens.

Create a diagram of the original connections (or take a picture) so you can restore it if it doesn't work.

Mike

[Richard Wagner]

My thanks to everyone. The motor that I was using cannot be reversed (no start winding leads exposed). I acquired a different used motor and was able to locate the start windings (buried inside the motor). I got some technical assist and the the motor is now functional and is switchable.

[Charles Lent]

You have received some good information so far. Reversing the connections of the start or the run winding will reverse the motor, but you should also know that the motor will not reverse while it's running. You must shut off the motor and after it stops reverse the connections and then turn it back on. If you try this while the motor is running it will just continue running in the same direction.

Charley

[Larry Fox]

What do I need to know before I attempt to reverse direction of an AC motor that is NOT identified as being reversible?

The phone number, location and business hours of the local motor shop. I had a 3-hp motor from a Unisaw that I needed reversed and the leads to do so were NOT accessible, it was clear this motor was not intended to be reversed. I took it to my local motor shop and the guy did a little head scratching about whether or not he could do it. He told me to go and get a cup of coffee and that he would call me if he could do it. 30 minutes later I had a motor that was reveresed and it ended up costing me about $25 + the cost of the cup of coffee (which I was going to get anyway).