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220/120 motor question, can't tell which one to use!

1454 Views 6 Replies 5 Participants Last post by  qbert
I got a air compressor at an estate sale that has a 3/4 hp motor. The tag on the motor is pretty much worn off, but it indicates it's a 115/230V. I can't tell which wires are the lead for the 115. Is there a way to determine which leads to use for 120? I've googled model number and frame number of the GE motor but I couldn't find anything.
Any help would be appreciated!
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How many wires are there, and what are their numbers? Pay particular attention to whether it's a P or a T lead.

If it's a terminal board, what are the terminals labeled, as well as the wires that attach to the terminals.

Terminal boards are tricky to connect without diagrams, there are a vast number of different types.

If this motor has the two power feed wires going into it, and no other internal wires connected to the terminal board, then it is not reversible rotation. This makes it somewhat simpler.

Usually, the internal connection between is a link that can be moved by loosening the screws. Most of the time, the link is 2-3 for 115 volts, and 3-4 for 230 volts.

If the motor is connected for 230 volts, and is supplied by 115 volts, it will try to turn, maybe it actually will, maybe not. In any case, no damage will result as long as the power is applied for less than 20 seconds or so.

If the motor is connected for 115, and 230 is applied, it'll usually trip the breaker before any damage is done. If the breaker doesn't trip, it'll make a lot of noise, and burn up in about 10 seconds. If it has a built-in overload, usually this will trip before any damage, but not always.

It sounds like it is already connected for 115, but with so many different types of terminal boards out there, the only sure test is to energize it with 120 volts and see what happens.

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