How to wire up a GEC 2 pole capacitor run motor

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How to wire up a GEC 2 pole capacitor run motor

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  • #748415
    Greensands
    Participant
      @greensands

      I have acquired a vintage single phase GEC 2 pole motor running at a nominal 2880rpm with a starting capacitor rated 40-50uf. The motor has 6 leads coloured Red, Black, Yellow and Green plus 2 White. A test meter check shows that the resistance between Red and Black leads gives 26.3 ohms and 42.8 ohms between leads Yellow and Green and I assume that the 2 White leads are connected to the capacitor.

      Perhaps before making any serious mistakes someone could advise me on how the motor should be wired up to the mains.

      IMG_0850IMG_0849

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      #748464
      Emgee
      Participant
        @emgee

        I believe the wire colours are blue and yellow which denotes the start winding. (not green)

        Red and black will be the run winding.

        The 2 white wires may possibly be across the centrifugal switch, check for resistance across the ends.

         

        Emgee

        #748485
        Clive Foster
        Participant
          @clivefoster55965

          Greensands

          That motor looks vaguely familiar. Maybe 45 or so years ago I had one of similar size and wire colours with just GEC and a type number on the side and on indication of connections.

          Fortunately I contacted GEC before letting the magic smoke out.

          Turned out to be a 2 or 3 speed motor (can’t recall which) for industrial fan drive applications made as a special for an air conditioning system maker. Hence no type number. I gather special in such cases referred to mounting and shaft length configurations. Slightly whacky switching arrangement too if I recall right.

          If it is a fan motor it’s not much use for anything else.  Effectively they are a sort of two phase motor. They are designed for maximum efficiency at the rated speed but the torque characteristics are pants at driving a variable load. High current flow off load and when loaded enough to drag the slip outside the design range.

          I put a lovely looking single speed fan motor on a drill in the days before I knew about such things. Cooked it in about 3 months. It would get stupidly hot spinning off load. Would get almost too hot to touch in the time needed to shift a job on the table over to the next hole.

          Yes I knew I should have stopped the drill to reposition but what 19 year old is gonna do that. Rush headedness rules at that age. Probably hormonal.

          Wouldn’t surprise me if my cooked motor was rated for a very limited number of starts before the excess heat generated in run up caused the windings to deteriorate. If it were basically designed to run 24/7 a couple of hundred starts would be overkill.

          Clive

          #748507
          John Doe 2
          Participant
            @johndoe2

            It’s definitely a single phase motor is it ?

            I only ask because Blue, Yellow and Red remind me of the traditional three phase colours, I think ? and the Black could be the star/neutral point and the two Whites for a thermocouple or bi-metallic thermal switch perhaps ?

            Just a thought – which is probably completely wrong – and which of course would not need a start capacitor  🙂

            #748508
            Greensands
            Participant
              @greensands

              I have checked for continuity across the two white wires and the resistance is zero ohms which suggests that the two wires may be connected to a centrifugal switch in its normally closed position but short of dismantling the motor I cannot be sure that this is the case.

              #748521
              peak4
              Participant
                @peak4
                On Emgee Said:

                I believe the wire colours are blue and yellow which denotes the start winding. (not green)

                Red and black will be the run winding.

                The 2 white wires may possibly be across the centrifugal switch, check for resistance across the ends.

                 

                Emgee

                Looks about right to me, though I’m not an expert on GEC motors;
                This is from a Brook catalogue
                image_2024-08-23_113637098

                You could try spinning it up with a soft start variable speed electric hand drill and see if the contacts open twixt the two white wires.
                In reality, it should probably fire up with just the run winding connected, though it might require a spin by hand in one direction.

                Bill

                #748522
                Baron J
                Participant
                  @baronj17589

                  Small motor

                  #748554
                  Greensands
                  Participant
                    @greensands

                    The mystery deepens. I tried a test run wiring the motor according to the diagram shown above on the assumption that the 2 White wires were connected to an internal centrifugal switch but the result was some nasty blue smoke emerging from the ventilating grills and the motor getting very hot. Fortunately I was able to switch off at the mains before hopefully doing too much damage.

                    Opening up the two end plates reveals the two white wire leading to an external location in one of the end plates but for what reason I have no idea. The photos hopefully illustrate the situation.

                    IMG_0851IMG_0852

                    #748566
                    Baron J
                    Participant
                      @baronj17589

                      Hi Greensands,

                       

                      That device on the end frame is a thermal cutout, it should have a protective red plastic button over  it.

                      Normally it would have mains voltage on it. Don’t touch it when power is on !

                      Simply applying power to red and black should allow the motor to be started just by spinning the motor shaft without making any other connections. Are you sure that the capacitor is OK and not shorted. The run winding will have a slightly higher resistance than the start one.

                      It is possible that the motor was damaged before you got it.

                      HTH.

                       

                       

                      #748568
                      Greensands
                      Participant
                        @greensands

                        On giving the spindle a twist the motor will quite happily run with the mains connected across the Red and Black.  What i have seen done in the past under similar circumstances is to include a Normally-Off/Push-On hand switch to take the place of an internally fitted centrifugal switch to provide the necessary phase shift for starting and keep the two White leads out of circuit and disconnected.

                        #748591
                        Baron J
                        Participant
                          @baronj17589

                          Hi Greensands,

                           

                          If you now connect one capacitor lead to the red wire and the other capacitor lead to the blue wire and the yellow wire to black, the motor should start and run when you connect power to it.

                          If it runs the wrong way just swap the blue and yellow wires. Just keep an eye on the temperature for a while, just to check that its not overheating. Ignore the white wires.

                          I suspect that the motor is just a capacitor start and run, no centrifugal switch. If there is one you will hear it click as the motor slows down.

                           

                           

                          #748600
                          noel shelley
                          Participant
                            @noelshelley55608

                            red / black should be the run windings. Blue/ / yellow start windings. White wires thermal cut out. I don’t think this type of motor has a centrifugal switch.  capacitor across the start and run windings. Good luck. Noel.

                            #748646
                            Greensands
                            Participant
                              @greensands

                              Thanks for all the info. In the absence of a centrifugal switch arrangement perhaps a wiring diagram showing a motor circuit with a permanently wired in capacitor would be of use.

                              #748659
                              Baron J
                              Participant
                                @baronj17589

                                Hi Greensands,

                                 

                                The diagram that I posted above is quite correct, just ignore the CF switch.

                                “If you now connect one capacitor lead to the red wire and the other capacitor lead to the blue wire and the yellow wire to black, the motor should start and run when you connect power to it.”

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