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Discussion Starter · #1 ·
I am working in industrial workshop. I am feeding 3 phase 480V to PDBs which feed into two 20A, 3ph breakers, as well as a 20a 2ph breaker. 3ph breakers feed power controllers and later 3ph heater systems down the line, while the 2ph feeds 24v motors/control system.

I had an incident occur where ONE of the 3ph breakers as well as the 2ph breaker tripped. One 3ph breaker (as well as most other 3ph equipment in this facility) held power.

What should I be looking for as root cause? Breakers were reset and machine runs fine now. This issue happened about 6 months ago with no root cause found then.

Thank you
 

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you didn't provide any information on the equipment that was attached to the two breakers that tripped, nor did you give information as to what diagnostic or even visual inspections of the breakers, conductors, equipment, or panel busses was performed or results thereof, yet you want someone to guess as to the cause.

good luck with that.

hire an electrician.
 
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Discussion Starter · #3 ·
Thanks for quick response!

The issue was out-of-scope of provided details. Next time I'll put something further together with more detail. :biggrin:

Solution: 120v control circuit firing SCRs within Power Controller connecting to 480V. Intermittent due to temperature changes within cabinet is guess or maybe faulty unit.

-E
 

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Fill in your profile please

Thanks for quick response!

The issue was out-of-scope of provided details. Next time I'll put something further together with more detail. :biggrin:

Solution: 120v control circuit firing SCRs within Power Controller connecting to 480V. Intermittent due to temperature changes within cabinet is guess or maybe faulty unit.

-E
Can you please complete your profile it helps us respond at the correct level
 

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I see several voltages mentioned, 480v, 120v, 24v (ac or dc?).. and are the breakers rated for the correct voltages and amperages?, any CPT's? Wire sizes also plays a huge role... motor load inrushes? ALOT of unknowns....
And to echo wildleg.... If you're not sure, and dont feel like dying from 480v electro-therapy, might be best to hire a licensed control guy
 

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2ph? Where are you getting 2 phase power? Do you mean 2 pole?

At first you say 24v control, then it's 120v control. Which one is it?

120v control SCR's, connecting 480v..........what? Motor?

Normally SCR's don't go "intermittent" due to temp variations.
If it was a faulty unit, and it works now, is it "fixed"?
 
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