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Thread: NEMA Code J Motor

  1. #1
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    NEMA Code J Motor

    I have motor test data from Baldor that shows LRC = 56.69A on a NEMA code letter J motor. As I understand this, the LRC is based on this identifier and for this motor the range is 7.1-7.99 kVA/hp. The motor is 5.2hp which gives me a range of 46.33-52.1A at 460v. So what does this mean? It seems to me the motor is outside its design basis. Aside from the OCD sizing issues, is this a problem? What I'm really wanting to know is, should I reject this motor based on this information?

  2. #2
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    Check this out. It appears as though your motor is within the expected starting KVA.
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    Last edited by templdl; 09-21-12 at 10:54 PM.

  3. #3
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    I must not understand this then. As I read this, my locked rotor (starting) current should be between 46.33-52.1A at 460v for a 5.2 hp code J motor. Is this right? If so, the test current of 56.69A is outside this range. Is this not correct?

    So, if my math is correct, the question is still the same, is this something I should be concerned about? Is this indicative of a problem with the motor?
    Last edited by mityeltu; 09-23-12 at 05:11 PM.

  4. #4
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    Sorry, you are correct. Personally I would question it. If you can communicate directly with the Baldor and ask them if they have Code J in the NP what would they expect LRA be for their motor. Baldor is a decent company. Is it made in the USA? They question the reason why they found it acceptable to ship the motor as they did.
    If they can justify it would be interesting to know why. Either way it is not consistent with the code J. Then, if you rejected the motor where does that lead? Are you guaranteed a motor that reflects the NP rating? Or, from a practical point of view just what are the ramifications should you accept the motor? The LRA of the motor is about .5a more that the max which I don't see it as an issue.
    The LRA would influence the thermal overload that protects the motor. You would have to consider the OLR heaters and see if you may have an issue there. With a higher LRA how fast does the motor come up to speed? If it has a lengthy acceleration time the higher LRA may be and issue making it unusable which would be a consideration should you decide to follow through with replacing the motor?
    Would you have combination starter with an MCP I don't see that as being an issue. But the thermal OLR should be considered.

    Again, it depends upon if you want to go through with replacing the motor based upon the conflict on the NP or because the motor is not usable. It is of my opinion that starting the motor and getting it through the acceleration phase without trip the OLR would be the issue.

  5. #5
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    Thank you. I had not yet considered the TOLs. That's a good point. I'll look into that first thing in the morning.

    Thanks.

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