Load calculation of multiple VFD driven motors

[Electriman]

Greetings,

I was wondering if NEC 220.50, 430.24, 430.25, 430.26 is applicable to size a feeder that feeds a combination of direct driven motors and and VFD driven motors.

Thanks in advance

 

[Electriman]

Any recommendation?

 

[Jraef]

Are you only thinking of the conductors?

430.26 would apply to AHJ discretion, so unless you have that, ignore it. 430.25 applies to factory listed equipment, otherwise you use 430.24. So really, 430.24 is what applies. What I did was apply 430.122 (125% of the VFD INPUT current rating, not the motor) if that was the largest load, then follow the rest of the rules accordingly.

 

[Electriman]

I am also thinking about load analysis for service size.