A Little help please

[YZERMAN2010]

Ok, I have been trying to figure this job, the more I look at it the more confused and frustrated I get. I am licensed and SHOULD know how to do this. I am hoping you guys would please help, Im about to tell the customer I cant do it. I can do the work, just need some confidents in my numbers...

Feed: 480v 3phase bus, using 100a ITS switch fused at???Info says primary is 56a.

Trans: 45kva 480 Delta Primary, 400Y/231 secondary. says 68a max. This is a German press, they want me to adjust taps after we energize to get seconday voltage to 400v

Total Load: 47kVA


This press will operate 24/7, so I need to size my primary and secondary feeders 125% for continuous duty. Press has motors, heating elements....

Primary: 56a*1.25=70a= 3#4 and#6 ground in 1" emt
Seconday: 68a*1.25=85a=4#4 and #6 ground in 1 1/4 emt

Am I way off? What should Primary fuses be sized to? Am I correct in sizing to 125%?

Thanks....Frustrated

 

[bob]

Your basic calculations are correct. Did not check wire size. I would assume you would use a 90 amp breaker for the secondary. Depending on the motor size along with the heat, the 90 amp may not be large enough. Is there a name plate that gives the MAX OCP and the MIN conductor size? Is this transformer part of a package that came with the press? We knowingly do not install transformers overloaded.

 

[YZERMAN2010]

Bob, seriously, thanks for your reply. The xformer did arrive before the press. It is part of the "package" . It will be dedicated to this press. I will have primary as well as secondary protection so I think I can fuse up 250%. Trying to rifle through code book to make sure it is necessary to size conductors to 125%.

Thanks Bob!!

 

[K8MHZ]

Ok, I have been trying to figure this job, the more I look at it the more confused and frustrated I get. I am licensed and SHOULD know how to do this. I am hoping you guys would please help, Im about to tell the customer I cant do it. I can do the work, just need some confidents in my numbers...

Feed: 480v 3phase bus, using 100a ITS switch fused at???Info says primary is 56a.

Trans: 45kva 480 Delta Primary, 400Y/231 secondary. says 68a max. This is a German press, they want me to adjust taps after we energize to get seconday voltage to 400v

Total Load: 47kVA


This press will operate 24/7, so I need to size my primary and secondary feeders 125% for continuous duty. Press has motors, heating elements....

Primary: 56a*1.25=70a= 3#4 and#6 ground in 1" emt
Seconday: 68a*1.25=85a=4#4 and #6 ground in 1 1/4 emt

Am I way off? What should Primary fuses be sized to? Am I correct in sizing to 125%?

Thanks....Frustrated

Does the label on the press allow for 60 Hz? If the press is 400 volts from EU, it may be designed for 50 Hz. Inductive reactance increases with frequency.

 

[YZERMAN2010]

Does the label on the press allow for 60 Hz? If the press is 400 volts from EU, it may be designed for 50 Hz. Inductive reactance increases with frequency.

Talked with manufacturer and said it was all set up for 60hz, press and xtransfor. Thanks!