Thread: How do you slow down an electric motor?

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5 hp motors that run on 120 vac are pretty rare since they draw so much current.

First thing to check: has the motor been changed? 120 VAC single phase motors normally come in two flavors; 1725 rpm and 3450 rpm. Obviously, if some nimrod changed motors and put a 3450 in place of a 1725, things get awfully fast! You should be able to find at tag....if not, borrow a mechanical tachometer that you hold against the end of the motor shaft. If you cant find one, take the motor to an electric motor repair guy....they are normally really cheap to deal with and can probably either fix your motor or suggest what to do. Clamp the leads and determine the draw:

AMP DRAW
Motor Size 120 volts 240 volts

1/4 hp. 6 amp. 3 amp.
1/3 hp. 7 amp. 3½ amp.
1/2 hp. 10 amp. 5 amp.
3/4 hp. 14 amp. 7 amp.
1 hp. 16 amp. 8 amp.
1½ hp. 20 amp. 10 amp.
2 hp. 24 amp. 12 amp.
3 hp. 34 amp. 17 amp.
5 hp. 56 amp. 28 amp.


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