Baldor Air Compressor Motor Issues
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  1. #1
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    Default Baldor Air Compressor Motor Issues

    Hi all,
    I have a Baldor motor (L1430T) 5hp single phase Iím planning on using to run my Champion air compressor (HR5-8). Problem is, the motor makes a loud humming noise, the same ugly sound a motor makes when the start caps go bad and the motor tries to start, but cant. The only difference is, this motor starts right up and runs, but makes that same awful sound while running. It pulls about 30 amps using a clamp-on meter running with no load on a bench top . Name plate says 20.6 amps, but with no load, I would expect something much less. I thought maybe the internal start switch was not disengaging the caps, so I took it apart, but its working fine. I then suspected a bad run cap, so I pulled the one from my other Baldor motor (L1410T) and put in the (L1430T). This made no difference what so ever. Thing is, canít read the label of the run cap in the (L1430T), but the (L1410T) has a run cap value of 50 mfd 370VAC. Not sure if it would make much difference using a run cap with a value of 10 mfd higher or lower since the two motors are virtually identical.
    Any ideas what else might cause this problem?
    Thanks in advance.

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    Bad start cap that stays in the circuit because the motor does not actually get up to speed? Measure the RPM. Fix is easy. Call Baldor for parts and data.

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    Bearings? compare run down times.
    Bill D

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    If you have a megometer, measure the windings. If not, take it to a motor shop that can measure it. It is pulling too many amps.

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    Quote Originally Posted by Joe Gwinn View Post
    Bad start cap that stays in the circuit because the motor does not actually get up to speed? Measure the RPM. Fix is easy. Call Baldor for parts and data.
    Hi Joe, Thanks for your response.
    The start caps are new and the motor starts up fine. Not sure what rpm the motor reaches, but the centrifugal switch is opening, you can also hear it close when the motor winds down after power is removed.

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    Quote Originally Posted by Bill D View Post
    Bearings? compare run down times.
    Bill D
    Hi Bill,
    The bearings are good; the shaft spins nice and easy by hand with no noise.

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    Quote Originally Posted by Bob-J-H View Post
    If you have a megometer, measure the windings. If not, take it to a motor shop that can measure it. It is pulling too many amps.
    Hi Bob,
    I only have a digital ohm meter, so I measured the resistance between the windings just for the heck of it. Donít know what they should read, or if these values reveal any problems or not, 2.4 ohms on the start winding, 1.6 on the Run. There is an infinite reading between each winding and the motor case, so at least itís not shorted to ground.
    Attached is a diagram.
    Attached Thumbnails Attached Thumbnails baldor-motor-wiring-diagram.jpg  

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    Quote Originally Posted by S.C. View Post
    Hi Joe, Thanks for your response.
    The start caps are new and the motor starts up fine. Not sure what rpm the motor reaches, but the centrifugal switch is opening, you can also hear it close when the motor winds down after power is removed.
    Hmm. Is the supply voltage correct for the motor wiring configuration?

    Can you measure the capacitor capacitance? Actually, there are two capacitors. Are they both good? Many digital multimeters can measure capacitance.

    The other possibility is a partly shorted winding.

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    Quote Originally Posted by Joe Gwinn View Post
    Hmm. Is the supply voltage correct for the motor wiring configuration?

    Can you measure the capacitor capacitance? Actually, there are two capacitors. Are they both good? Many digital multimeters can measure capacitance.

    The other possibility is a partly shorted winding.
    Joe,
    Yes, the supply voltage is correct for the motor wiring configuration
    The 2 start caps measure out at 230-235MFD each. The label says they are 216-259 MFD 250V, so they should be good. The old run cap is around 53MFD, but I can't read the label and donít know what its value should be.

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    I called Baldor today and talked with a service tech, I told him about my motor issues and he was happy to answer questions. After giving him the motor serial number and spec. number, he gave me the correct values for the caps; he also gave me the motor winding ohm values. He even told me the exact day, month and year the motor was made, I thought that was pretty cool. Another thing he mentioned was that the run cap must match the values of the original, no deviations. The bad news, he said the very same thing Joe Gwinn mentioned about a possible shorted winding.

    Later, after talking with him, I decided to recheck all my previous readings since mine were different. As I started checking the windings, I again came up with different readings, so I got my el cheapo meter out and rechecked. Ok, great, my new readings are now very close to what Baldorís specs are. Apparently, my expensive meter (Fluke) is having issues now, go figure.

    Since the winding values are close to whatís considered factory new and not shorted to the case, Iím just going to order out new caps and see what happens. Iím hoping itís just a bad run cap.

    If anyone is interested, attached is the updated wiring diagram with the Baldor specs along with my new readings.
    Attached Thumbnails Attached Thumbnails baldor-motor-wiring-diagram-corrected-.jpg  

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    I will throw my in my .02 FWIW.
    The capacitor check function on the bog standard DVM is quick dirty check. A cap can read okay using this method but if tested it with dedicated capacitor tester a lot of times you find it leaky as hell. As capacitors age they essentially turn into resistors. As we are not dealing with the front end of a radio receiver, caps are cheap just replace them.
    I would also suggest megging the motor, again your standard DVM only uses about 1.5 VDC to measure resistance. You need voltages in 1000 volt and up range to perform PI and DAR (dielectric absorption ratio)tests which will give a much better indication of the state of the insulation on the windings. But all that said a motor shop is probably your best bet cause a good megger will cost serious coin. There are low cost ones available from usual scum bags. Problem with them is they don't carry UL and other stamps of approval. I don't know about you but I want a piece of gear that can believe the readings and if I make a mistake and hook something up wrong it will not blow up in my hand.
    Apologies for going OT but I feel it is important to realize the limitations of the test gear you are using. Both from a safety stand point and acquiring data that is accurate enough for what you are attempting to do.

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    Only other thing is measure voltage at line and load side of start control whether it is a contactor or a pressure switch. Bad contacts can make all the difference.

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    Quote Originally Posted by S.C. View Post
    Yes, the supply voltage is correct for the motor wiring configuration.
    The 2 start caps measure out at 230-235MFD each. The label says they are 216-259 MFD 250V, so they should be good. The old run cap is around 53MFD, but I can't read the label and donít know what its value should be.
    Even if 53 MFD isn't what the factory ordered, it should work well enough.

    My suspicion is that one of the two windings has a shorted turn or three. This can be impossible to detect with an ohmmeter.

    So, I'm thinking that this problem requires specialized tools to figure out. As others have said, I'd talk to a motor shop.

    If it is in fact a failed winding, I'd guess that buying a new motor is cheaper than rewinding the old motor.

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    Quote Originally Posted by Joe Gwinn View Post
    . . . I'd guess that buying a new motor is cheaper than rewinding the old motor.
    Maybe not. The 5hp US made Baldors list for around $1000 these days.


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