480 volt Circuit Breaker Testing

[bean9677]

When performing an instantaneous trip test on a 480 V circuit breaker. What is the max amperage difference I would want to see between each phase of the breaker?

 

[big john]

You're not comparing phases to each other, you're comparing each phase to the published trip curve for that breaker plus the error tolerance for that curve.

I don't test many MCCBs so I wouldn't be the person to ask there, but for power circuit breakers the tolerances I often see are 10%, though it does vary.