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11-16-2010, 07:15 AM #1
Help me wire single phase motor for reverse?
I did search. I still am unclear after reading a few posts on this.
I've got two motors that are now running CCW (facing the shaft). They are both capacitor start, single phase, one hp, motors. Both have a single capacitor attached and audible click on/off centrifugal switch. Both are wired for 120v. However both of them only have four terminals.
The first one has four marked, clockwise from the bottom, L2, 4, 2, and COM. LO appears between 4 and 2. Otherwise the motor is lacking any other placards or markings.
The second has terminals marked, from bottom, simply 1, 2 ,3, nd 4. AC in was connected to 1 and 4. I tried swapping the leads on 2 and 4 to no avail. Motor did not even run.
There is a placard on this one.
I cannot find any information on these motors online. Can anyone suggest how to reverse direction on them? I think the first motor was actually reversed at some time in the past, but I did not write down how to do it. This time I'll scratch in somewhere.
The second one may be another case. I wonder if it's possible to get inside and measure for the starter winding and reverse the leads on the one with highest resistance. I've read about this, but am not clear what is meant exactly by "reversing" them. If I can follow the leads off of the start capacitor into the frame won't this indicate the starter winding? Easier yet, could I simply locate that centrifugal switch and reverse the leads at this point?
Thanks for any suggestions.
11-17-2010, 08:57 AM #2
Single phase motors will run in either direction, so a "starting" winding is put on the stator which is fed via the " start" capacitor and a switch. When the motor is stopped the switch is closed and at some speed the switch opens. So the thing to do is to work out the circuit, of where the capacitor is connected to via the switch and where the other end of that winding goes to. When you have done this switch over the connections to that start winding. Often the start winding is actually just a tap on the main winding, which rather complicates things.
11-17-2010, 11:34 AM #3
Thank you. Since I posted I took the rear face off and looked into the wiring. I'm afraid that your description of a tap off of the main winding might apply. I tried tracing the wire that fed the centrifugal switch but it appeared to be the same wire that led to the primary winding, which suggests that there is, as you pointed out, a tap within instead of a separate wire coming from the starter winding.
Now I have to mount the motor backwards which requires modifying the belt guard and extending the length of the lathe by about a foot.