Tripping Breaker on Wye Delta start

[recman55]

I have a two motor Baler with two 75hp 460v 3 ph motors with wye delta start. The motors run two piston hydraulic pumps. One motor is tripping the breaker on start. The breakers are a 125 amp breakers, one for each motor. The loaded amps on both of the breakers are 120 amps. Amps to the six delta legs are 63 amps.
There have been only two of these balers made. I have found other engineering errors in the equipment. Is the breaker to small for the motor? What is typical breaker sizing for wye delta start curcuits?

 

[itsmoked]

Have you read this thread?

http://www.eng-tips.com/viewthread.cfm?qid=321490

Keith Cress
kcress -

http://www.flaminsystems.com

 

[recman55]

I read the thread you referred to, after further investigation it appears the motor is tripping after it has started in the bale compression cycle.
( full motor load) One moter pulls 120 amps the other 190 amps. I turned down te pump pressure, Set it by amps to the same as the other motor amps. Let's see what happens!

 

[jraef]

Read article 430 of the NEC, a 125A breaker is too small for a 120A load!

"Dear future generations: Please accept our apologies. We were rolling drunk on petroleum."
— Kilgore Trout (via Kurt Vonnegut)
For the best use of Eng-Tips, please click here -> faq731-376

 

[recman55]

Thanks for you feed back. It has not tripped today since I matched the two motor loads.

 

[jraef]

It does not change the fact that your breaker size is illegal.

"Dear future generations: Please accept our apologies. We were rolling drunk on petroleum."
— Kilgore Trout (via Kurt Vonnegut)
For the best use of Eng-Tips, please click here -> faq731-376

 

[automatic2]

I don't think that 'not greater than' make it illegal, not practical for sure.