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  • New motor not working? Confused.

    Seriously, I think I need to find a good electronics forum. I post more electrical questions here... it is getting embarrassing This is a brand new motor. No joke. I bought it months ago, but for any number of reasons I have only now hooked it up. This is meant to be driven by a VFD. Hook it up; it makes strange noises, and the VFD faults "Overcurrent" every time. Figure it is the drive, so I connect to my standard 3-phase, RPC power to make sure. Blows the 20A fuse every time. Got real discouraged. This was yesterday.

    Today I decide to re-wire the motor per the connection diagram for "high voltage" (it is 230/460V). The darn thing runs fine! Trying to discern if this is a mis-labeled connection diagram, I search around and pretty much determine it isn't. Now I'm totally lost.

    On motor:




    The question is -- there IS something wrong, right? I don't want to drive out to my motor shop and get the "dumkoff!!" response Like I said, this is a brand new motor, so I am liable to lay the fault on myself first in this instance. There is nothing wrong with the standard power line it is connected to. It runs every other 230V three phase motor in my shop---even one of equal horsepower---with no issues whatsoever.
    Last edited by Arthur.Marks; 12-18-2011, 10:50 PM.

  • #2
    Video of motor wired for "low voltage" connected to 230V, 3-phase, RPC power: (p.s. it stops because it blows the fuse, not because I turned it off.)


    Video of motor wired for "high voltage" connected to 230V, 3-phase, RPC power:

    Comment


    • #3
      The label shows the 'standard' wire number assignments, so providing it is hooked up as shown it SHOULD run?
      Max.

      Comment


      • #4
        When you had it connected to the vfd, what type of ramp times were you using?

        When you had it connected to the rpc, the 20 amp fuse that you melted, was it a time delay fuse or fast acting?

        Dave

        Comment


        • #5
          The diagram is fine. At least it is internally consistent, as far as I can see.

          Clearly has a big issue in low volts..... does not appear to get up to speed, growls and complains

          WIRES might be mis-labeled..... like a backwards phase (reversed numbers) on one winding.

          In high voltage, is the current identical on each wire?



          if one winding is reversed, it would be messed up badly when in parallel, but not so messed up when in series but connected to low voltage.... although I would expect to see SOME change.

          Run on high voltage connection , and check motor currents.
          1601

          Keep eye on ball.
          Hashim Khan

          Comment


          • #6
            It may run on 240 when wired or 460, but that doesn't mean it's running fine. You would get very low power.

            Try a long ramp - say 20 seconds, when running on the vfd when wired for 240 - just as a test. Check the motor current on each leg - some vfd's allow you to see this, others just give you an average.


            Where are the fuses on the rpc. - input only, or on the output (you'd have three fuses on the output)?


            Oh... a quick trip to the motor shop may be your best option. They will tell you in minutes if there is anything wrong
            Last edited by lakeside53; 12-19-2011, 03:16 AM.

            Comment


            • #7
              Another question..... are you certain that it was wired correctly to begin with?

              Sometimes the wire numbers can resemble each other as you work.

              Try disconnecting ALL wires, and re-wiring it for low voltage relying only on the table and wire numbers as-labeled, with NO reliance on "memory", etc. Sometimes that allows one to see the numbers correctly and do it right. DAMHIKT

              Originally posted by lakeside53
              It may run on 240 when wired or 460, but that doesn't mean it's running fine. You would get very low power.
              That is obvious....

              The test is just that, a test to identify if there is a problem, and try to localize it. Nobody is suggesting to run the motor like that "because that's how it works best".... it is just a test to get at the issues.

              A motor shop may be an option, but it can be an expensive option, particularly when one has just laid out substantial cash on a NEW UNUSED motor which SHOULD be trouble-free and perfect.
              Last edited by J Tiers; 12-19-2011, 09:46 AM.
              1601

              Keep eye on ball.
              Hashim Khan

              Comment


              • #8
                Trying to get to all the questions posed...

                When you had it connected to the vfd, what type of ramp times were you using?
                Didn't matter. Started with 10 seconds, upped it drastically to no effect.

                When you had it connected to the rpc, the 20 amp fuse that you melted, was it a time delay fuse or fast acting?
                Strangely -- the time-delay, 15A, RK5 fuses on the RPC output don't blow. It is the 20A breaker on the main single phase panel.

                In high voltage, is the current identical on each wire?
                High voltage connections on the motor legs produce the following:
                T1, 1.5A
                T2, 1.3A
                T3, .8A
                And just for the heck of it, I checked the rpm while it was running with a contact tachometer: 1798 RPM.

                Check the motor current on each leg
                Low voltage connections on the motor legs produce the following when connected to RPC output and then the RPC turned on:
                T1-7, 2A
                T2-8, 26A
                T3-9, 26A

                NOW -- here is the strange, ah-ha part… I forgot to connect the motor to the RPC just now when I turned it on. What I find is that if the RPC is up and running already and then the motor connected:
                T1-7, 4.5A
                T2-8, 6.2A
                T3-9, 3.3A
                …and it runs fine! That still doesn't help me with the VFD, of course. Maybe it diagnoses an issue, though?

                Where are the fuses on the rpc. - input only, or on the output (you'd have three fuses on the output)?
                Output. One 15A, RK5 Bussmann for each leg. A total of three.

                are you certain that it was wired correctly to begin with?
                I've checked this numerous times and completely separated all the wires to go from low to high connection more than once. I am 100% confident in the wiring accuracy to the diagram.

                Does the VFD have torque boost ?
                Probably? I figure it does, but I didn't turn that "on". It is the second TECO N3 drive I've wired. There's been no issue with the other one---or the motor (also a Marathon Black Max), for that matter. Seems unlikely to be the real issue here.
                Last edited by Arthur.Marks; 12-19-2011, 10:45 AM.

                Comment


                • #9
                  Does the VFD have torque boost ? If that is set too high it will cause the motor not to start.

                  Comment


                  • #10
                    OK, your motor "runs", but... You are supposed to have your RPC ON before applying the load. If not you have two stalled motors it's trying to start, which is why you got the currents you recorded. You can get way with it on some RPC, but usually when the RPC is a lot larger than the target motor.


                    BTW... Your current settings - Often an unloaded motor will show different "idle" currents, especially on an "unbalanced" RPC You'd need to load it up to get better results. You do have a wide range though and 6.3A is way too high for one leg, especially unloaded .... what are your RPC voltages? And... based on your motor plate, I would have expected numbers in the 2.5 amp range (40-50% of max at idle). What are you measuring current with? As Jerry points out, numbers can be easy to confuse -6 and 9 are a problem unless they put the bar beneath to show. Undo all winding connections and take ohm readings.

                    VFD : if your rpc currents are valid, that's why it's tripping.
                    Last edited by lakeside53; 12-19-2011, 10:48 PM.

                    Comment


                    • #11
                      Originally posted by J Tiers

                      That is obvious....

                      The test is just that, a test to identify if there is a problem, and try to localize it. Nobody is suggesting to run the motor like that "because that's how it works best".... it is just a test to get at the issues.

                      .
                      Hey Jerry - have some more coffee - I was responding to the OP not to you. He already said he ran it on the high V settings.

                      Comment


                      • #12
                        Originally posted by lakeside53
                        Undo all winding connections and take ohm readings
                        This is one thing I have never done before and do not know how to connect to take a reading. I know how to set the meter to read resistance, but which two specific leads do I touch to take the reading? All current measurements were done with an Ideal AC/DC clamp adapter connected to an Ideal Test Pro 360 series multimeter. All other readings are done with the latter.

                        Voltage readings for the RPC are as follows. Standard single phase line from the main breaker box records 250VAC. Voltage between one of those incoming lines and the generated RPC leg reads 277VAC. Voltage between the other incoming line and the generated RPC leg reads 288VAC. RPC is a Phase-A-Matic model number R3 (3HP rated). That said, remember that the RPC has nothing to do with my VFD input. The VFD is a TECO N3, 2HP, 230V single phase input, 230V three phase output.

                        I have never understood how you "load up" a line to take voltage or amp readings. How can I take a heavy cut on a machine and be monitoring the multimeter? I don't have that many hands! I took the above readings with a small bench lathe turned "ON" and the back-gear engaged. I figure at least that is something.

                        Comment


                        • #13
                          When reading ohms, the color of the leads doesn't matter (unless you are checking diodes.) One lead on one side and the other lead on the other side.

                          http://www.idealindustries.com/media...uctions_v5.pdf

                          As for taking a reading under load, I would put my camera on remote, tripod it near the meter, focus and set the shutter and aperture, then go back to the lathe and start the heavy cut. When the cut is well established, I would trip the remote shutter. Then again, I might set up one of the video cams and have it connected to my computer, set where I could see it, but not spatter it with chips and coolant. Then again, I might set up my lathe for auto feed, slow speed and jump around a bit.

                          However, you might not have the equipment to allow for that. That is where a friend, wife, offspring or kidnapped mailman might come in handy.

                          Pops

                          Comment


                          • #14
                            Results

                            Thank you, armedandsafe. Here is what I found for resistance:
                            T1-T4 = 0.0
                            T2-T5 = 0.0
                            T3-T6 = 0.0
                            T7-T8 = 0.0
                            T7-T9 = 0.0
                            T8-T9 = 0.0
                            All other readings were "OL", or infinite Ohms. I guess this is supposed to tell me two things... There isn't a short in the motor (if there was, the reading wouldn't be 0.0?) and the actual order of the windings inside the motor. Those conclusions are just a guess, but looking at the results it would seem to make the most logical sense.

                            So I'm looking at one of two things (I guess): incoming single phase line voltage is too high (250V) ...or... a VFD issue. I'm trying my hardest to make sense of all this. Thanks for the help so far, everyone. I really appreciate it. I know I'm a slow, independent learner so bear with me
                            Last edited by Arthur.Marks; 12-19-2011, 06:27 PM.

                            Comment


                            • #15
                              If you want a load just wire a 3 "heaters" or 300/500 watt halogen light bulbs across each phase, or.... a lathe in the highest gear. I use a 3 phase heater. On an rpc, you really only need 2 heaters/loads - T1-T3, T2-T3.

                              Your rpc appears unbalanced. For now, and some load, put the lathe in the highest gear - not the lowest (back gear)... it's not a high load, but usually sufficient. 280/250 is 12% high. It will still work so move on to the motor problems.


                              Your resistive measurements.. if those are correct, You need another meter! Zero is a short, but your measurements are likely because your meter range can't resolve low ohms readings. Try it on the 200 ohm range and publish the results.

                              This is your likely motor connections: NOTE that "the other end" of 7,8 and 9 are joined in side the motor. Verify this by metering 7-8, 8-9, 9-7.





                              My prior point about the VFD - IF you are drawing 6.2 amps on one leg on the rpc (and your measurement is valid) then you try it on your vfd - your VFD can't provide that current and will trip. And... 6.2a is not correct for that motor loaded or unloaded, and more so looking at the other measured legs - you have a problem. Stay off the vfd until your resolve it on the rpc.
                              Last edited by lakeside53; 12-20-2011, 12:26 PM.

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