354 amps on a 70 amp 3 phs breaker

[power 4 people]

Got a call, 20 hp Vacuum motor wont stay on. Newly installed after being moved from previous location that had commercial 3 phs power. Now that panel is fed from a 40hp phase converter. client turned on the breaker and flipped the switch. motor ran for about 3 seconds and breaker tripped. I turned off breaker and began to check wiring. Found a wire on the motor contact load side that missed the lug when tightened and was possibly in contact or near but not tightened under lug. I installed that wire correctly and started up the motor again. Ramped up to 354 on my amp clamp before breaker tripped.

Could it be damaged control form improper wiring?

Motor needs a Soft Start installed?

Damaged motor from improper wiring?


Voltage is 240 phase to phase. 208v A phase to ground, B, and C, both 120v to ground.

Motor diagram shows it is wired for 208-230v

Fan is spinning in correct rotation.

 

[infinity]

Ramped up to 354 on my amp clamp before breaker tripped.

How long did it run? 54 amps*125%=67.5 amps. You could increase the breaker size (54*250%) if it's tripping only due to the starting current.

 

[hillbilly1]

Several things, how far from panel? What is the breaker size? Remember, on single phase input, the current will be much higher. 40 HP phase converter should be sufficient for a 20 HP motor.

 

[jim dungar]

I agree, you need a larger breaker.

 

[power 4 people]

How long did it run? 54 amps*125%=67.5 amps. You could increase the breaker size (54*250%) if it's tripping only due to the starting current

 

[power 4 people]

Thanks everyone. I appreciate the extra brain power!

 

[petersonra]

208v A phase to ground, B, and C, both 120v to ground.

Somehow this does not seem right to me.