Looking for some insite on 430.6(C). If I have a motor control center with fifty(50) 1hp, 480V, 3 phase motors each with a variable voltage variable speed drive (VFD). What is the minimum feeder size and overcurrent protection size based on the 2005 or 2008 NEC?
If I don't know the drive or motor nameplate then I am assuming that that calculation is as follows:
49(drives) x 2.1A(Table 430.250) x 1.5 (Arcticle 430.6C) = [154.35] + [1(drive) x 2.1A(TAble 430.250) x 1.5(Arcticle 430.6C) x 1.25(Article 430.24)] = 158.29A
Use a 175A circuit breaker and #2/0 conductors
If I Know that we are using X-brand drives at 65K AIC with 3.5A input current:
[49 x 3.5A] + [1 x 3.5A x 1.25] = 175.88A
Use a 200A circuit breaker and #3/0 conductors.
Prior to 2005 the calculations look something like this:
[49 x 2.1A] + [1 x 2.1A x 1.25] = 105.53A
Use a 110A circuit beaker and #1 conductors.
Am I miss interpreting anything?
If I don't know the drive or motor nameplate then I am assuming that that calculation is as follows:
49(drives) x 2.1A(Table 430.250) x 1.5 (Arcticle 430.6C) = [154.35] + [1(drive) x 2.1A(TAble 430.250) x 1.5(Arcticle 430.6C) x 1.25(Article 430.24)] = 158.29A
Use a 175A circuit breaker and #2/0 conductors
If I Know that we are using X-brand drives at 65K AIC with 3.5A input current:
[49 x 3.5A] + [1 x 3.5A x 1.25] = 175.88A
Use a 200A circuit breaker and #3/0 conductors.
Prior to 2005 the calculations look something like this:
[49 x 2.1A] + [1 x 2.1A x 1.25] = 105.53A
Use a 110A circuit beaker and #1 conductors.
Am I miss interpreting anything?