Help wiring AC motor

Discussion in 'General Electronics Chat' started by darkbreeze, Oct 11, 2012.

  1. darkbreeze

    Thread Starter New Member

    Oct 11, 2012
    14
    1
    Greetings to all. I'm not sure this is the correct place to ask for this information, but I've had little to no luck finding any assistance elsewhere so I thought perhaps somebody here could guide me in the right direction. I've got an older AC motor for an air compressor that was given to me just to get it out of their way and it's wired for 220. I need to change the configuration to 110, which it's capable of, it's a 115/230 motor, however the diagram is not entirely clear to me. Currently there are four wires coming out of the motor, theoretically, per the diagram, both hot. They are wires A and D. Wires B and C are wired together. The diagram indicates this is the configuration for 220. The diagram for 110 shows all four wires parallel, but does not indicate what they should be hooked to or if all are used. Do A and B both connect to hot and then C and D both connect to neutral, or vise versa, or does it matter? Do wires B and C just get capped and not used? Can A and B be hooked to neutral and C and D be hooked to hot? Also, since A and D are currently used in the 220 configuration, I know which wires they are, but how do I determine which of the two wires that are connected together are B and which is C? I'd really appreciate anybody who is proficient with AC motors to pipe in and let me know. Thanks in advance.
     
  2. JoeJester

    AAC Fanatic!

    Apr 26, 2005
    3,373
    1,159
    The two coils are in series for 220 operation.

    When BC are disconnected, you should have an open between A, C, and D and low resistance between A and B

    Can you connfirm that? Mark your wires if they are not already marked.
     
  3. darkbreeze

    Thread Starter New Member

    Oct 11, 2012
    14
    1
    Thanks Joe for the reply. I've closed the shop down for the day but will test as you indicated and post the results tomorrow. I think you're correct in that wiring b and c together causes it to be in series I'm just not positive on whether all four wires are needed and if so, the exact connections, for the 110. Other air compressor motors I've used, in fact, the one that's on the unit right now, not the one in the picture, has a completely different setup. It has white, black and green, hot, neutral and ground, for 110 and it has to just be hooked with both white and black to hot for 220. Of course, this other motor I'm trying to use is about a billion years old too but I took it apart and cleaned the years of grime and bugs out and all the windings look good as do the brushes and the armature. I'll post after testing. Thanks.
     
  4. shortbus

    AAC Fanatic!

    Sep 30, 2009
    4,010
    1,530
    When you say brushes and armature, do you mean that it is a "universal" motor? If so watch running it with no load on it. They have been known to "run-away" (over speed) with no load.
     
  5. darkbreeze

    Thread Starter New Member

    Oct 11, 2012
    14
    1
    No, it is not a "universal" motor, at least not that I know of. Actually, after a bit more research, it turns out that it is a repulsion start induction motor. Apparently these are fairly uncommon but reputedly are strong long lasting motors.
     
  6. darkbreeze

    Thread Starter New Member

    Oct 11, 2012
    14
    1
    After testing the wiring, and doing a bit of research, it turns out this is a bit different than the specs you asked me to test. What I do have, is two sets of windings. I have continuity between two pairs. So I have two sets of in and out, so to speak. Since I know which wires are A and D, I've connected the wire out of the other two wires, B and C, to their mates. So, A and B, which do NOT have continuity, are together, to be connected to hot. C and D, which do not have continuity, are to be connected to neutral. This should give me two separate 110V circuits to supply two separate sets of windings. This brings me to my next set of questions though. First of all, should I use one set of wires to feed both circuits or do I need to bring two completely separate 110V lines in to feed each winding? Also, is the single 110V cutoff switch used by the compressor to kill power to the motor at the specified cutoff pressure going to be sufficient since two sets of windings will be drawing current through it? I just don't know if the points in the switch will be capable of handling the load or if I somehow need to use two switches which I don't want to do because I can't imagine trying to sync them. I don't want one set of windings out of sync and getting power, even for a second, when the other has already cut out. Perhaps a pressure switch for a 220V circuit, but wired 110, would have points capable of the load? Ideas, thoughts?
     
  7. BSomer

    Member

    Dec 28, 2011
    433
    106
    You will only need one 110V circuit to feed power to the motor. Your cut off switch needs to be rated for the motor current at the voltage it is being supplied with. So at 110V the motor current is 12.5A. Try to find a model # or other info on the cut off switch so you can find out what its switching current rating is. You would probably want something in the range of 15 - 20A current rating.
     
  8. darkbreeze

    Thread Starter New Member

    Oct 11, 2012
    14
    1
    Ok, thanks for that info. In the back of my mind I knew it would come down to amperage rather than voltage for the switch but I wasn't certain enough to assume anything. I realize amps and volts are two different beasts. Any thoughts on my assumptions regarding the connections I've made. Likelihood of pretty lights and smelly noise?
     
  9. BSomer

    Member

    Dec 28, 2011
    433
    106
    Your connections seem sound to me. I did notice in one of your pics that the leads coming out of the motor seem really short. Are you able to make a good and safe connection to those wire leads?
     
  10. darkbreeze

    Thread Starter New Member

    Oct 11, 2012
    14
    1
    Yeah, I soldered and double shrink tubed some extensions on there to test it and it turns silently and fast. Of course, there was no load on it so I didn't let it go for more than about ten seconds but I could tell it had power. I also had removed the back and adjusted the brush ring fully to one side as it was about three adjustment slots over from the end. I'll let you know how it goes. I have to exchange the pulley I bought for the other motor before I test it with the pump as it was a 5/8" shaft and the B-line is a 3/4".
     
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