Power Conversion Equipment as per 430.122(A)?

[dohiviyu]

The exact text of the code is:

(A) Branch/Feeder Circuit Conductors: Circuit conductors supplying power conversion equipment included as part of an adjustable-speed drive system shall have an ampacity not less than 125 percent of the rated input current to the power conversion equipment.

The part that gives me pause is, "as part of an adjustable-speed drive system."

Just curious how the code instructs us to calculate the ampacity of the mains power.

 

[roger]

Since this not a "how to do" as in DIYer type question we will allow it.

Roger

 

[paulengr]

The exact text of the code is:

(A) Branch/Feeder Circuit Conductors: Circuit conductors supplying power conversion equipment included as part of an adjustable-speed drive system shall have an ampacity not less than 125 percent of the rated input current to the power conversion equipment.

The part that gives me pause is, "as part of an adjustable-speed drive system."

Just curious how the code instructs us to calculate the ampacity of the mains power.

You’ve got it backwards in the section you’re in. It is going to be a branch circuit or a feeder. We start with the drive name plate load, size the wiring to feed it, and size the breaker/fuses to protect the wiring. There is a drive design issue where if the transformer is too big you add a line reactor, isolation transformer, or fuses specified by the manufacturer but that’s a UL thing (install as per manufacturers instructions).

The service wiring is similar. The only big difference with feeders and service conductors as far as ampacity is that you take diversity into account where at branch circuits that would undersize them.

Protection until you get into distribution systems is almost always viewed from the power source to the loads. So we size s breaker to disconnect a load if for instance current exceeds a limit. It also protects the source from faults on the load side.