DC Motor circuit voltage drop.

Discussion in 'General Electronics Chat' started by subman, Sep 1, 2012.

  1. subman

    Thread Starter New Member

    Sep 1, 2012
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    For a 125 VDV 1.6 W motor, is it necessary by NEC to consider inrush current in the calculation to size the conductor for the motor circuit?
     
  2. #12

    Expert

    Nov 30, 2010
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    1.6 watts will only use .0128 amps at 125 Volts DC. I can't remember the NEC saying anything about milliamp level circuits and I can't think of any reasonable size wire or circuit breaker that will not survive that load.
     
  3. subman

    Thread Starter New Member

    Sep 1, 2012
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    Sorry #12 (or #32 incognito?). I failed to type the k in front of W. The motor is 1.6 kW.
     
  4. #12

    Expert

    Nov 30, 2010
    16,320
    6,818
    Section 430 of the NEC is a very long chapter. I found 2 places that say to use the locked rotor current for ampacity and several tables calling for a percentage based on use. Then there is table 430-152 about dc motors less than 50 hp:

    non-time delay fuse = 150% of FLA
    dual element fuse = 150% of FLA
    instantaneous trip breaker = 250% of FLA
    inverse time breaker = 150% of FLA

    So much writing that you have to declare pretty much everything about what it is and how you're going to use it.
     
  5. subman

    Thread Starter New Member

    Sep 1, 2012
    3
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    Thanks fore your help. Have a good weekend.
     
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