jeremy.zinkofsky
Senior Member
- Location
- nj
I understand that it is not a good design practice to treat the line side wiring of a VFD as a motor circuit. Makes perfect sense as VFD input conductors will never see the inrush current on motor start-up.
My question is "Do i have a choice whether or not to ignore article 430 when sizing the OCPD feeding the VFD?"
It is clear to me that 430.120 Adjustable-Speed Drive Systems requires table 430.52 to be used when sizing the OCPD, no consideration or exception that limits the size of the OCPD to 125% of VFD rating.
So, IMO it is totally legal to choose the rating of the OCPD feeding the VFD to be greater than 125% of VFD rating as long as the values in table 430.52 are not exceeded.
Let me know if you agree or not.
My question is "Do i have a choice whether or not to ignore article 430 when sizing the OCPD feeding the VFD?"
It is clear to me that 430.120 Adjustable-Speed Drive Systems requires table 430.52 to be used when sizing the OCPD, no consideration or exception that limits the size of the OCPD to 125% of VFD rating.
So, IMO it is totally legal to choose the rating of the OCPD feeding the VFD to be greater than 125% of VFD rating as long as the values in table 430.52 are not exceeded.
Let me know if you agree or not.