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  • electric motor problem

    not a wizard with motors, advice please. 1 hp baldor motor powering a simplex hydraulic pump for press. have not used it a lot,but no problems until today. started bending a piece of mild steel, when suddenly breaker trips, motor stops. reset breaker (20 amp) does it again. tried outlet on different breaker, same thing. motor plate says 7-8 amps (115) motor was HOT to the touch. (can't hold hand on it )

    http://www.tksimplex.com/html/produc...ump%20Platform

    if link works, it is similar to the pump shown,but with solenoid valve. thoughts?

    thanks,bmw

  • #2
    Is your start switch sticking closed. You should hear a click as the motor slows to a stop. If not pull the end bell and look for burnt welded contacts on the switch.

    Bob

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    • #3
      Sounds like the pump got blocked, or otherwise won't turn, and motor stalled.

      Or maybe the motor failed.

      Stuck start switch could do that too, but is hard to find without disassembly or having the motor actually start.

      You need to see if the motor will work when driving the pump free flow, or when not driving the pump at all (disconnected manually). That should indicate if the motor is any good.

      be aware that the motor windings could have shorted to ground and so the case could be live if you take it off the pump assembly.

      It is likely to be a positive displacement pump, and so if flow is blocked, the pump will be blocked, and that will stall the motor. Was it a bigger piece than usually bent?

      I notice it is a cap start motor, which makes it a little easier to find a bad start switch.
      Last edited by J Tiers; 06-29-2015, 11:51 PM.
      1601

      Keep eye on ball.
      Hashim Khan

      Comment


      • #4
        I didn't look at it after work tonight -- too tired - actually a smaller piece than what I usually work with. I will have to pull the pressure hose off, try that, proceed from there I guess.
        thanks for the advice, I will post what I find in a day or so. bmw

        Comment


        • #5
          +1 on stuck start switch or a blocked pump dragging rpm
          down into start mode.

          -D
          DZER

          Comment


          • #6
            haven't disconnected the pump from motor yet,but did pull the assembly off of the reservoir. motor seems to be running at normal speed, no funny noise, ran approx. 15 seconds,tripped breaker. later today I will start dis-assembly of motor, I guess.
            bmw

            Comment


            • #7
              Look for a stuck relief valve on the pump.

              As for "normal speed"... even a few % slip of the rated speed (load in excess of the rating) will cause an over-current situation.

              Comment


              • #8
                I am leaning towards switch-- it has tripped while running pump,(pressurizing cylinder) , while not pressurizing cylinder, and with pump out of reservoir (no oil in pump) there is a small switch/relay ? in line from the on/off toggle has 4 wires some go into the motor housing. wonder what it is/does?
                bmw

                Comment


                • #9
                  Originally posted by bmw625 View Post
                  I am leaning towards switch-- it has tripped while running pump,(pressurizing cylinder) , while not pressurizing cylinder, and with pump out of reservoir (no oil in pump) there is a small switch/relay ? in line from the on/off toggle has 4 wires some go into the motor housing. wonder what it is/does?
                  bmw
                  Which switch?

                  When the start cycle is over the switch should open. EASY way to find out......

                  Get your clamp-on meter, any kind so long as it will show the current you have, although an analog meter with a needle is best. Clamp it on a mains wire. Start motor.

                  If the start switch is working, motor will start, and the current will spike up, come down, and then suddenly drop to maybe 1/3 of what it was. If switch is not working , the current will stabilize at a higher level, and you will not see a sudden drop.
                  1601

                  Keep eye on ball.
                  Hashim Khan

                  Comment


                  • #10
                    Originally posted by bmw625 View Post
                    I am leaning towards switch-- it has tripped while running pump,(pressurizing cylinder) , while not pressurizing cylinder, and with pump out of reservoir (no oil in pump) there is a small switch/relay ? in line from the on/off toggle has 4 wires some go into the motor housing. wonder what it is/does?
                    bmw
                    Your motor may be fitted with a external Potential relay instead of internal centrifugal sw.
                    It senses voltage across the start winding and cuts out the capacitor.
                    Max.

                    Comment


                    • #11
                      Originally posted by MaxHeadRoom View Post
                      Your motor may be fitted with a external Potential relay instead of internal centrifugal sw.
                      It senses voltage across the start winding and cuts out the capacitor.
                      Max.
                      could this relay fail and cause breaker to trip?

                      Comment


                      • #12
                        Two causes, if the motor is overloaded and the relay does not drop out due to not coming up to speed, or the contacts are welded/remain closed.
                        Max.

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                        • #13
                          if what I think is the "relay" is actually a relay (4 wires ,spade connected , one from power) it got hot in the short time it took to trip breaker.
                          bmw

                          Comment


                          • #14
                            That sounds like a motor overload relay which has a thermal current element which gets hot and causes it to trip after a delay. If properly sized, it should trip before the breaker, but if the motor is close to the rating of the breaker, it may trip first, because it has a shorter delay.

                            http://electrical-engineering-portal...lay-protection
                            http://electrical-engineering-portal...otection-relay



                            The relay itself is usually part of a motor starter, which also includes a contactor that actually opens and closes the power to the motor.
                            Last edited by PStechPaul; 07-04-2015, 10:35 PM.
                            http://pauleschoen.com/pix/PM08_P76_P54.png
                            Paul , P S Technology, Inc. and MrTibbs
                            USA Maryland 21030

                            Comment


                            • #15
                              this is the motor http://www.baldor.com/catalog/JL3509A at least most of the numbers match my motor. the small box on mine has a smaller box attached,holding the "relay"
                              bmw

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