Is it possible for circuit breakers to fail due to high harmonic distortion caused by SMPS?

Our systems are 380VAC, 3 phase, 200Amp FLA and do produce harmonics. The harmonic levels we have measured are as high as 60%/FND.

I have read about nuisance tripping (heating bi-metal) caused by harmonic distortion due to increased RMS, but never read anything about heating of contacts.

Thank you for your input.

Bruce

 

It is to be noted that a contact in a circuit breaker has resistance, and so is subject to heating when there is current. Thus the same reasoning, that RMS current being higher that fundamental current when harmonics are present causing more heat, applies to contacts of circuit breakers also.

So check whether your actual RMS current is within the rated fundamental current of your circuit breaker.

 

Short answer is yes

Harmonic distortion of that level looks a lot more like DC to all components of the circuit and the subsequent heating will eventually take it's toll

Question being why would the end customer want to pay the increased electrical cost of a significantly reduced .pf for every piece of equipment on the distribution system servicing that piece of equipment ?

From a Forensic Engineer's perspective only after bench testing the breaker, plotting the curve, and recording IR readings will you know the full extent

 

Thanks for the feedback.

Wouldn’t the IR loss cause the Bi-Metal to open and trip the Breaker before the contacts heat up to the point that would cause the Breaker to Fail (melt internal structure)?

Thanks