Testing 3 Phase Motor Windings - Page 2
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  1. #21
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    Thatís a curious question you asking about 3 and 6 being backward. If that were the case and I hooked up only a single set of windings as you suggest, what would the result be. I wouldnít think it would matter.


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    One test is worth a 1000 opinions.

    Tom

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    Fast thought on it is if the 3-6 were backward and all the windings connected, that would set two windings bucking each other, and at the least, torque would be poor, as in very bad, with nearly missing pole(s). Probably also be much higher current, because there would be low back EMF on that leg....and the "neutral point" would be pulled off-neutral, throwing other coil voltages out as well.

    With just one set, I think pretty similar, because one pole set would be reversed.... it would be out of order, so it would be "pushing " when it should be pulling. That should kill torque, probably also mess up the phase of back EMF.

    I'd have to think about that in more depth, but it's late.

    Short story is don't do that, because it will foul up motor operation in at least one way if not more.

    BTW.... there IS a way to check for shorted turns. I have not tried it, but it ought to work. Battery, and a neon bulb/resistor like an old time cheap power tester. (see below, a meter with needle and dial is better)

    Connect the neon across the coil. Touch the coil across the battery, and check the neon flash. A good winding should give a decent flash. A shorted turn will suck the energy out of the winding, and the flash will be weak or non-existant.

    The neon is not the best test unit, but it is easy. Better would be a simpson meter, or any with a needle. Set the voltage range to whatever gives a good kick on the needle. A shorted winding will have a much weaker kick, even if it is just one turn shorted.

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    Quote Originally Posted by TravisR100 View Post
    Getting the motor out is the issue. On a lathe. Everything about it SEEMS ok except it bogs taking a .040 cut which seems light. It otherwise runs at the rated speed and makes no noise.
    I would suggest you look at the mechanical drive end, especially if it is belt driven. The belt drive could be slipping at higher loads.

    Encountered this problem before on a wood shaper spindle that was a 10 HP, with a wye/delta start. The machine had 6 spindles, but only one would stall out during the cut. We spent a lot of time troubleshooting the wye/delta starter and the motor wiring. Took the motor to a shop and had it dynomometer tested, tested good. Its still stalled. Ordered and replaced the motor, it still stalled.

    Turns out the belt drive was slipping. It had a wide flat belt running at 3600RPM. The shop maintenance guys weren't tightening it correctly. The machine was supplied with a cam wrench to hold the motor tight while tightening the mounting bolts. They were unaware of that wrench. Once the belt slipped, plastic particles from the belt would melt and embed in the pulley metal.

    Manufacturer recommended cleaning sheaves with a abrasive pad and replacing the belt, then using the cam wrench to tension the belt. Never had another problem with any of the spindles.

    It looks like your motor has been rewound already, the junction box is a 4" octagon box designed for romex house wiring cables, and those metal wire tags are the type a rewinder uses, not something most motor manufacturers use.

    SAF Ω

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    Safety pitch- I used teach industrial electrical safety. 100s of people die each year at work due to electrical related injuries. This doesnít even touch the 20-30,000 of injuries that occur nationwide, and yes this includes the morons on metal step ladders in swimming pools working on overhead lights.

    Be careful, get help if needed

    Run the machine, take currents on all the phases going to the motor. You need a clamp-on style amp-probe. NOT a Fluke or any other Volt-ohm meter(multi-meter takes in-line (in circuit) amps, usually milliamperes or max of 10)

    FYI fluke now makes a nice multimeter that meggers at up to 1000v. Check out the 1587

    1) are the amps equal within a small margin on all 3 phases?

    2) do the measures Amps match the name plate data for full load amps.

    Horsepower and Amps have a direct relationship. 5hp at 220v 3phase is 12 amps.

    Running the machine at no load obviously doesnít equal zero amps due to motor, gear train-and bearing inefficiency, as well as things like windage losses(air movement) of the motor rotor and even things like the chuck jaws.(that fan the chuck jaws makes at 2000rpm is getting energy from somewhere!)

    If you measure 9 amps on all 3 phases , it doesnít mean something is wrong, it may mean you are using only 3.75 HP





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    Ripperj and SAF thanks.

    SAF I didnít realize manufacturers didnít use those tags. I think as a first step Iím going to at least disconnect all the leads and verify that there isnít a gross mislabeling of the lines (continuity between 1 & 4, 3 & 6, 2& 5, 7, 8, & 9). That still wonít tell me if there is a reversal on 3&6, 2&5, or 1&4.

    I also like the idea of trying to run it on each set of windings separately and checking the result.

    I do have a cheap clamp on meter here somewhere so I can test the amp draw as well.

    As for checking for belt slippage, Iím going to need a helper to visually look under the machine while I take a cut that seems to bog it down.




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    Your lathe do what you want .
    In my opinion (30 years industrial controls), you are starting troubleshooting at the wrong point.
    I spent 3 years as a kid working in an electric motor repair shop


    Did the machine ever work?

    Isnít that motor just a normal 5hp 3phase motor that can be wired for 220v or 480v? You need to show the whole name plate


    You canít configure it to run on just one set of windings without letting the smoke out.

    Donít do anything until you take run currents unless the motor sounds horrible , vibrates a lot or does not appear to come up to speed

    This is a random pic of a typical 220/480, looks like yours right?

    Note that itís single speed , you will fry it trying to run on one set of windings!





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    Sounds fine, doesn't vibrate, comes right up to speed. Full data plate below. Very hard to read. It says:


    TYPE V0-J
    Volts 220/440
    Min RPM 500
    Max RPM 3470
    PH 3
    Code H
    Design B
    HP 5
    LO volt amps 17.5
    HIGH volt amps 8.8
    Rating 55 C
    Serial 2822956




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    ripperj
    ^^^^You know that from experience? One set of windings will provide the needed magnetizing force. The machine will not have as much power but it should run fine on light loads.

    Tom

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    TravisR100 is the test you just posted one or a full set of windings? Any other modifications?

    Tom

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    Not familiar with that. Iíd guess based on limited info that the varidrive part is an adjustable sheave vee belt.
    The voltage and amps support the motor being a pretty typical dual voltage, single speed motor.
    The min/ max speeds are probably the adjustable sheave
    Wild ass guesses based on two pics. I have been wrong before and will be again


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    Quote Originally Posted by TDegenhart View Post
    TravisR100 is the test you just posted one or a full set of windings? Any other modifications?

    Tom
    The test I just posted? The resistance test in the first post?


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    Quote Originally Posted by ripperj View Post
    Not familiar with that. Iíd guess based on limited info that the varidrive part is an adjustable sheave vee belt.
    The voltage and amps support the motor being a pretty typical dual voltage, single speed motor.
    The min/ max speeds are probably the adjustable sheave
    Wild ass guesses based on two pics. I have been wrong before and will be again


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    Thereís is also an RPM rating in addition to min max but I canít read it. It is a motor controlled adjustable sheave belt. Itís on a Rivett 1020S.


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    Quote Originally Posted by TDegenhart View Post
    ripperj
    ^^^^You know that from experience? One set of windings will provide the needed magnetizing force. The machine will not have as much power but it should run fine on light loads.

    Tom
    Iím not claiming to be an engineer, without a winding book, how are you going to split the windings out, the nine wires are tied internally to their respective coils. I havenít thought about this in 30 years, but I donít see how you can do this external to the stator, and thatís complicated.
    Iíd be worried about drawing excessive currents on whatever coils you decide to power up and burning them up.

    Regardless any of the above: good troubleshooting determines what the delta is between actual and expected conditions.

    OP says machine wonít take a heavy cut.

    Could be the belt, could be a clutch, could be .......



    Diving into the motor when the OP indicated that it seems to be running fine seems silly to me .
    Damaging the motor with a less than a 4.0 plan seems like potential destructive testing to me

    Iím out,
    Good luck



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    Quote Originally Posted by TravisR100 View Post
    Sounds fine, doesn't vibrate, comes right up to speed. Full data plate below. Very hard to read. It says:


    TYPE V0-J
    Volts 220/440
    Min RPM 500
    Max RPM 3470
    PH 3
    Code H
    Design B
    HP 5
    LO volt amps 17.5
    HIGH volt amps 8.8
    Rating 55 C
    Serial 2822956




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    Is this with one set of windings or a full set or what?

    Tom

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    Quote Originally Posted by TDegenhart View Post
    Is this with one set of windings or a full set or what?

    Tom
    Never seen a data plate have specs for anything other than both sets of windings either in serial for high voltage or parallel for low voltage.


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    Default Testing 3 Phase Motor Windings

    Quote Originally Posted by ripperj View Post
    Iím not claiming to be an engineer, without a winding book, how are you going to split the windings out, the nine wires are tied internally to their respective coils. I havenít thought about this in 30 years, but I donít see how you can do this external to the stator, and thatís complicated.
    Iíd be worried about drawing excessive currents on whatever coils you decide to power up and burning them up.

    Regardless any of the above: good troubleshooting determines what the delta is between actual and expected conditions.

    OP says machine wonít take a heavy cut.

    Could be the belt, could be a clutch, could be .......



    Diving into the motor when the OP indicated that it seems to be running fine seems silly to me .
    Damaging the motor with a less than a 4.0 plan seems like potential destructive testing to me

    Iím out,
    Good luck



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    You just energize one set at a time. Theyíre already split out since itís a dual voltage motor.

    Iíll take current readings this evening and post that first.


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    Quote Originally Posted by TDegenhart View Post
    ripperj
    ^^^^You know that from experience? One set of windings will provide the needed magnetizing force. The machine will not have as much power but it should run fine on light loads.

    Tom
    Doing some Googling it seems what TDegenhart is describing is commonly done and is called a "part winding start." In typical applications one set of windings is energized first and then after a time delay (2 to 5 seconts) the other set of windings is energized. I couldn't find anything about running a motor continuously with only one set of windings energized. Some articles also mentioned that the shaft may not even turn until the second set of windings was energized.

    One of the articles:

    Part Winding Motor Starters

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    " I couldn't find anything about running a motor continuously with only one set of windings energized."

    This is how most idler motors are run when making a rotary converter. One just needs to have the rotor at near
    nameplate speed so it does not stall to a stop when the winding is energized.

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    As much as I hate to come back here and admit this, whoever had ďbelt slippingĒ as the cause of the problem wins the prize.

    I remembered I had built a multi output tachometer for the lathe. I just went and hooked it back up. It simultaneously displays spindle rpm, motor shaft/pulley rpm, and the reeves pulley output rpm. This way I can monitor all three without having to look under the machine while I instruct someone else to take a heavy cut.

    When I start the lathe all the RPM readouts are as they should be. Motor spinning at 1800 RPM, reeves output spinning at 900 RPM, and spindle spinning at 900 RPM. As soon as I take a heavy cut both the reeves output and the spindle slowdown equally. This tells me the belt on the varidrive is slipping and not the belts further down in the drive train. I can also visibly observe this if I look down at the reeves output pulley while taking the cut.

    The crazy thing is it SOUNDS like the motor slowing down. But the tach shows it at a rock steady 1800 RPM. Itís obviously all the other rotating parts in the gear train that Iím hearing slow down.

    Unfortunately this will probably be one of the more difficult problems to correct and donít yet have a clue how Iím going to tackle it. But to keep this thread to its title Iíll make another post elsewhere for advice on that.

    Thank you to everyone who responded to this thread however. Even though it turns out it wasnít the motor I learned quite a bit about how everything is wired during my troubleshooting.


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