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View Full Version : Reversing an electric motor?


Doug Krebs
12-08-2003, 05:01 PM
I know koldpecker is good with this kinda stuff.

I bought a used air compressor and the motor has been replaced. I was cleaning it up and noticed it had an arrow on the pulley of the pump pointing counter clockwise. Well the motor is turning the pump clockwise. It still pumps a decent amount of air, but I imagine it would do a lot better if it pumped correctly.

So any of ya'll know anything about motors? It's a single phase, 220, 1.5 HP, century electric motor. I think you can mess with the starting solonoid some how and make it spin the opposite direction.
robertf03
12-08-2003, 05:11 PM
its been a while since i've messed with anything like that, but I think theres some diode type deal inline that makes it act like a DC power source to the motor and you can just reverse the wires.
eight
12-08-2003, 05:29 PM
That's only on a reversible motor. The motor in your drill is just a dc motor. If this compressor motor is reversible it will have diodes like flem said and you have to switch the wires after the diodes.

But I seriously doubt the compressor is spinning backwards if it is working at all. Compressors use reed valves, kind of like a one way check valve for air. The one on the intake lets air in and closes it from coming back out, and the one on the exhaust lets air out and prevents it from coming back in. If you tried to spin it backwards the exhaust reed valve would have to let air in, which don't happen. And intake one let air out, which don't happen. Now its not a bad idea to take the reed valves out and clean or replace them on an old compressor, if they're bad they just decrease efficiency.
Doug Krebs
12-08-2003, 05:41 PM
Thats what I was thinking too, but why would the pulley on the compressor be pointing the opposite direction?
eight
12-08-2003, 05:44 PM
Maybe the arrow is pointing the wrong way. Pulley might not be the origional, or maybe its the origional put on backwards. A grinder should remove the problem.
robertf03
12-08-2003, 05:44 PM
remove the pulley and turn it around so the arrows pointing the other way :D
Doug Krebs
12-08-2003, 05:50 PM
Originally posted by robertf03
remove the pulley and turn it around so the arrows pointing the other way :D

Thats what I was thinking... If they replaced the motor maybe they took the pulley off the compressor for some reason. I'll take the belt off and spin the pump backwards by hand and see what it does.

Or I could be smart and call the company and ask them which way the compressor needs to spin!
fbronco86
12-08-2003, 07:27 PM
what kind of compressor? tank size and all that good stuff? how much scfm?