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  • electric motor

    would anybody know what kind of motor this might be? it sais 230vac/50hz, 940 ma, 2790 rpm. there is 60 ohms between two wires, the third apparently has no connection. so i thought a one phase motor, nothing happens however when i connect it. there is something about a vfd mentioned on the label, so maybe a three phase motor after all? it is very clean and appears not to be damadged. Click image for larger version  Name:	0 050.jpg Views:	0 Size:	2.66 MB ID:	1856165 any thoughts before i fry the thing?
    Last edited by dian; 02-18-2020, 03:49 PM.

  • #2
    It is obviously a 2pole AC induction motor.
    The Red/Blue/Green leads all appear to be winding connections?.
    I would think it a 1ph PSC motor, but this should indicate two winding of equal resistance with a centre tap.
    If there is the same resistance between any two conductors, it would be 3ph.
    What is the motor plate info?
    If you got it second hand, it may have an open thermal switch/fuse etc?
    Max.
    Last edited by MaxHeadRoom; 02-18-2020, 03:04 PM.

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    • #3
      What makes it obvious?

      -D
      DZER

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      • #4
        Originally posted by Doozer View Post
        What makes it obvious?

        -D
        2790rpm on 50hz = 2 pole.
        Squirrel cage rotor = AC induction.
        Sorry edited, 50Hz.
        Max.
        Last edited by MaxHeadRoom; 02-18-2020, 03:55 PM.

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        • #5
          Originally posted by dian View Post
          ... the third apparently has no connection. ...
          What do mean "apparently"? Do you mean because the the red & blue are connected, there's nothing left for the green to connect to? If so, you're missing it. A 3 phase motor will have connections between all wires: red & blue, red & green, and blue & green.

          A 3 phase will run on one phase, but need a kick to start. So wrap a cord a couple of times around the shaft, connect 230 between any 2 wires, & give the cord a pull.

          Edit: try all 3 possible connections. It needs to run all 3 ways if it's 3-phase.
          Last edited by Bob Engelhardt; 02-18-2020, 04:55 PM.

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          • #6
            Originally posted by Bob Engelhardt View Post

            What do mean "apparently"? Do you mean because the the red & blue are connected, there's nothing left for the green to connect to? If so, you're missing it. A 3 phase motor will have connections between all wires: red & blue, red & green, and blue & green.

            A 3 phase will run on one phase, but need a kick to start. So wrap a cord a couple of times around the shaft, connect 230 between any 2 wires, & give the cord a pull.
            How are you going to provide the needed phase shift?
            A typical RPC ran this way shifts the 3rd phase with suitable value capacitors.
            I have found that the motor is likely to drop out of run with any kind of loading placed on it.
            Max.
            Last edited by MaxHeadRoom; 02-18-2020, 04:10 PM.

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            • #7
              Originally posted by MaxHeadRoom View Post

              How are you going to provide the needed phase shift?
              A typical RPC ran this way shifts the 3rd phase with suitable value capacitors.
              I have found that the motor is likely to drop out of run with any kind of loading placed on it.
              Max.
              My suggestion was only to determine if the motor is 3-phase, not to use it that way.


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              • #8
                I see.
                But I would think a resistance check should give a very good idea.
                The info on the motor plate would normally tell all!
                Max.

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                • #9
                  The green wire is visibly connected to a winding, blue and pink/tan likewise, but the nature of that winding is unknown. Three wires could be three phase, possibly PSC, or ???

                  How about a pic of the motor tag that seems to be present on the right in the picture? Guessing games are not fun, motor tags often have useful info on them.

                  Originally posted by MaxHeadRoom View Post

                  How are you going to provide the needed phase shift?
                  A typical RPC ran this way shifts the 3rd phase with suitable value capacitors.
                  I have found that the motor is likely to drop out of run with any kind of loading placed on it.
                  Max.
                  The typical "static phase converter" does exactly that, and will run the motor at 50% or a bit more, of full power. Starts the motor with a start capacitor, then disconnects it to run on single phase just like a single phase motor.. (some include a "run capacitor", but it is questionable how much that does)
                  1601

                  Keep eye on ball.
                  Hashim Khan

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                  • #10
                    If there is no connection on one of the wires, it almost has to be an open winding, or an open connection. The windings don't look burned, so it may be a manufacturing defect, like a cold solder joint or bad splice. You may as well carefully peel back the insulation and examine the connections from the external wires to the windings, particularly the one that reads open circuit.
                    http://pauleschoen.com/pix/PM08_P76_P54.png
                    Paul , P S Technology, Inc. and MrTibbs
                    USA Maryland 21030

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                    • #11
                      There doesn't appear to be a start winding- all the wire looks to be the same gauge, and with 3 wires coming out I'd say it's 3 ph. If one has no reading, I think Paul has it right, there's probably a bad connection.

                      Having seen some videos showing how motors are made, it seems likely to me that a wire could have been weakened when the coils were installed. If this motor ever ran, it probably died because one coil went open. Could be in a visible spot, or not. On the other hand there could well be a bad connection where the leadouts connect to the magnet wire. Again, agreeing with Paul- follow that open wire into the bundling and start opening up the insulation. There's a good chance that you will find the problem.

                      I don't know if thermal breakers are included in any of the connections- if so one could be open.
                      I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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                      • #12
                        Single phase motors can have a thermal switch or fuse which opens the connection to the main windings, but that does not work for three phase, as loss of one phase would result in a single phase running condition. Instead, several thermal sensors are wired in series and connected to an external motor starter or controller.

                        https://electrical-engineering-porta...-for-beginners
                        http://pauleschoen.com/pix/PM08_P76_P54.png
                        Paul , P S Technology, Inc. and MrTibbs
                        USA Maryland 21030

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                        • #13
                          Originally posted by PStechPaul View Post
                          Single phase motors can have a thermal switch or fuse which opens the connection to the main windings, but that does not work for three phase, as loss of one phase would result in a single phase running condition. Instead, several thermal sensors are wired in series and connected to an external motor starter or controller.

                          https://electrical-engineering-porta...-for-beginners
                          Actually, in US style motors, which are often wye, it is very common to put a disc thermal sensor at the wye point. The disc normally shorts the three "neutral point" ends together as the wye connection, and when it trips, it opens all three at once.

                          The OP is in Switzerland, and that motor looks european, so it could be made quite differently.
                          1601

                          Keep eye on ball.
                          Hashim Khan

                          Comment


                          • #14
                            Originally posted by J Tiers View Post
                            The typical "static phase converter" does exactly that, and will run the motor at 50% or a bit more, of full power. Starts the motor with a start capacitor, then disconnects it to run on single phase just like a single phase motor.. (some include a "run capacitor", but it is questionable how much that does)
                            Not the ones I know of.
                            If talking RPC the ones I have built have a start capacitor and then a capacitor bank is used to create the 3rd phase,
                            WAY back Fitch Williams defined the method which has often been used.!!!


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                            • #15
                              Rotary phase converters create 2 additional phases.

                              -D
                              DZER

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