VFD input ocpd sizing

[Rhazel]

Hi all,
I am putting together a cabinet with (8) 20HP VFD's
Each pump will have a 20hp schneider VFD #ATV320D15N4C with max input current of 45.73A.
Schneiders documentation says Minimum breaker to be 50A but 45.73 * 1.15 = 52.58A which does not meet 430.128.
I want to protect the input of each drive and have a disconnecting means with a circuit breaker. Am i missing something simple here?

 

[petersonra]

Hi all,
I am putting together a cabinet with (8) 20HP VFD's
Each pump will have a 20hp schneider VFD #ATV320D15N4C with max input current of 45.73A.
Schneiders documentation says Minimum breaker to be 50A but 45.73 * 1.15 = 52.58A which does not meet 430.128.
I want to protect the input of each drive and have a disconnecting means with a circuit breaker. Am i missing something simple here?

The disconnecting means has to be 115%. the OCPD is sized according to 430.130 (A)(2).

if you want one device to serve as both the OCPD and the disconnecting means, it has to meet both requirements.

 

[infinity]

It says that it "shall be permitted to be in the incoming line" but does that include the branch circuit breaker? The incoming line originates at the circuit breaker so it sounds like an external disconnect to me.

430.128 Disconnecting Means.
The disconnecting means shall be permitted to be in the incoming line to the conversion equipment and shall have a rating not less than 115 percent of the rated input current of the conversion unit.

 

[Rhazel]

My cabinet will have (1) 300A MCB to a distribution block then i would like to break down the ocpd to the individual VFD's on the line side. the best analogy i can think of would be a large a/c with multiple compressors and other associated loads.