I recently took a job as an EE at a machine shop working on panels for machinery. The previous employees did some interesting things when it came to wiring the building. Such as wiring a 225KVA XFRM with a 480V Prim and 208/120V Sec. Useing the Sec as the Prim. So they could get 480v out of 208. Now I know in theroy this will work and I was told it has been working. My question is how wrong is it to do this and what could go wrong?
Wiring a 480 Prim 208/120 Sec xfrm
- Thread starter Nsmith
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You can review this thread to see how one transformer mfg approaches the situation:
http://forums.mikeholt.com/showthread.php?t=130473&highlight=Acme
Care must be taken to address grounding on the 480v side {see 250.21(B)}
and
Welcome to the Forum
http://forums.mikeholt.com/showthread.php?t=130473&highlight=Acme
Care must be taken to address grounding on the 480v side {see 250.21(B)}
and
Welcome to the Forum
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
It is not wrong.
Very little could could wrong unless they connect the X0 bushing on the LV side of the transformer. The transformer can overheat if this connection is made, due to current imbalances.
One common misapplication is in the area of grounding/bonding of the HV side. In previous code cycles 'ungrounded' 480V systems were allowed without having GF indication.
The manufacturer of you transformer should be able to supply you with an 'application note'.
Thanks,
The 208 on the xfrm is being fused with a 100 amp disconnect. The xfrm is also feeding two CNC lathes. The ultimate goal is to have this xfrm feed some equipment around the shop the is going to be tested and put up for sale. So I am thinking of having the 480V feed a 100 amp fused disconnect with a portable equipment recepticle and use SO cord for a temp hook up to the various equipment for testing. The CNC lathes are not being used anytime soon so the can be disconnected. Any suggestions would be appreciated.
The 208 on the xfrm is being fused with a 100 amp disconnect. The xfrm is also feeding two CNC lathes. The ultimate goal is to have this xfrm feed some equipment around the shop the is going to be tested and put up for sale. So I am thinking of having the 480V feed a 100 amp fused disconnect with a portable equipment recepticle and use SO cord for a temp hook up to the various equipment for testing. The CNC lathes are not being used anytime soon so the can be disconnected. Any suggestions would be appreciated.
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