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Mike G.
Mike G., Master Electrician
Category: Electrical
Satisfied Customers: 7487
Experience:  Proven Professional 48 years Experience
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if a 3 phase delta to wye transformer with 600V primary and

Resolved Question:

if a 3 phase delta to wye transformer with 600V primary and 208V secondary is used to supply power to a resistance seam welder with a delta transformer does that set up a short cct condition. there is a fused disconnect switch between secondary side and the welder.should a distribution panel be required and welder be fed by a breaker instead.welder is 50 kva . transformer is 75 kva
transformer is fed from 600v panel with 70 amp molded case breaker
Submitted: 5 years ago.
Category: Electrical
Expert:  Mike G. replied 5 years ago.
Hi, I'm Mike and I'll be glad to assist you.
1) What are you loosing the breaker or the fuses?
2) What is the load for the welder?
3) What sizes are the fuses?
4) What type are the fuses?
5) What size is the wire feed to the welder?
Customer: replied 5 years ago.
1) I would keep fused disconnect and add a panel with molded case breaker or just use fused disconnect switch.
2)full load on welder 208V is 139 amps.
3)fuses 150 amp.
4)one time fuses. should hrc fuses be used?
5)#1 copper.
Expert:  Mike G. replied 5 years ago.
You should be using an "R" fuse (time delay). one time will blow not allowing for inrush. A circuit breaker may be installed but a fuse will work if the right type.

Specifying the Right Fuse for Circuit Protection
Customer: replied 5 years ago.
need confirmation that fused disconnect switch is enough without adding panel and breaker and also that there will be no short cct condition.
Expert:  Mike G. replied 5 years ago.
I don't understand what you're asking for. The fuse or circuit breaker is the short circuit protection. Fuses or breaker are acceptable for use to protect the circuit and equipment. The only difference between them is that a circuit breaker will not allow the circuit to single phase. That would be when you lose one leg, A circuit breaker will open all 3 legs. With the right type fuse, you'll not have the problem caused by a one time fuse.
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