'blowing out' phases on motor protection breaker? 2

[robbm]

Just wondering if anyone has come across this. We have a basic motor control panel for a 7.5HP motor (460VAC, 3phase). The protection is a motor protection circuit breaker, rated/sized according to the motor. We tested it without issue and the customer is now claiming that they are 'blowing out 1phase of it' about once a week, and need to replace the breaker each time (and that's all they can provide for info). Still trying to get more info from them, but if anyone has any suggestions, by all means...My guess would be that motor may be the culprit if a single phase is causing the breaker to trip or even be damaged beyond just tripping, but thoughts/comments are welcome...

thanks in advance.

 

[jraef]

I see people using these things a lot lately because they are cheap and small and technically, the Interrupt Ratings are surprisingly high (some are rated 65kAIC all by themselves). But almost nobody stops to think what the term "self protected" means, and they find out the first time there is an issue. They are cheap enough to replace, but they should NEVER be re-used after a major fault.


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[robbm]

thanks guys, i wasn't aware that they were more or less 'oneshot' type devices. i havent heard from the end user since i told them to check their incoming power and the contactor also, so i think they may have found what they were looking for.
thanks again for all the comments.