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Discussion Starter · #1 ·
I do occasional work at a small mill in the next town. They dont employ electricians.

The service is 3 wire, no neutral, no ground, just the 3 hot legs. The secondary of the transformers is wye connected.

What do you call that configuration?
 

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I guess ungrounded Y. What does it feed?
 

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I’d call it dangerous if you aren’t careful. With that said, it’d be called a floating Star here. Generally speaking when you see them, and I worked at a r-mix co that had three, they are in Delta configuration. The Star configuration gets you a neutral to get a lower single phase voltage for lighting and what not.
 

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You can have a Y with no neutral it just means you can not use 277. Normally you would still have 3 phases and a ground which means you can still clear a single phase to ground fault.

So are you saying you only have 3 wires on the poles going to the transformers or 3 wires coming from the transformer?
 

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You can have a Y with no neutral it just means you can not use 277. Normally you would still have 3 phases and a ground which means you can still clear a single phase to ground fault.

So are you saying you only have 3 wires on the poles going to the transformers or 3 wires coming from the transformer?
Yeah…is the wye grounded X0? They didn’t really explain the secondary. Plus, aren’t there any convenience outlets in the entire mill, or is the entire thing ungrounded with no detection?
 

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Yeah…is the wye grounded X0? They didn’t really explain the secondary. Plus, aren’t there any convenience outlets in the entire mill, or is the entire thing ungrounded with no detection?
I’m going to guess it’s a floating system with no alarm or lights. The three plants I had before were that way and the owners were oblivious to the hazards. I told them finally the guilt, when something goes wrong was theirs alone.
Back to the OP, I wouldn’t be surprised if the original Delta bank died at some point and the poco replaced it with a Star bank made out of lot stock 277 xformers. The net effect is the same, they just didn’t have to ground the Star center.
 

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Discussion Starter · #10 ·
You can have a Y with no neutral it just means you can not use 277. Normally you would still have 3 phases and a ground which means you can still clear a single phase to ground fault.

So are you saying you only have 3 wires on the poles going to the transformers or 3 wires coming from the transformer?
3 wires leaving the 3 transformers, one wire each transformer. about a 20 foot drop to the first weatherhead/mast down to the feed to the MCC. no ground wire, no neutral wire, just 3 hots going to the mill
 

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Discussion Starter · #12 ·
I’d call it dangerous if you aren’t careful. With that said, it’d be called a floating Star here. Generally speaking when you see them, and I worked at a r-mix co that had three, they are in Delta configuration. The Star configuration gets you a neutral to get a lower single phase voltage for lighting and what not.
I agree, normally it is delta. BUT this is definitely Wye. I am looking for some one who is familiar with seeing this configuration to tell me what the common trade name is. I saw a post by someone, somewhere that talked about a floating delta but this is Y
 

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Discussion Starter · #14 ·
Yeah…is the wye grounded X0? They didn’t really explain the secondary. Plus, aren’t there any convenience outlets in the entire mill, or is the entire thing ungrounded with no detection?
there are 120V circuits in the mill, derived from 2 phase fed dry transformers
 

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Discussion Starter · #15 ·
I’m going to guess it’s a floating system with no alarm or lights. The three plants I had before were that way and the owners were oblivious to the hazards. I told them finally the guilt, when something goes wrong was theirs alone.
Back to the OP, I wouldn’t be surprised if the original Delta bank died at some point and the poco replaced it with a Star bank made out of lot stock 277 xformers. The net effect is the same, they just didn’t have to ground the Star center.
you are probably correct, i dont know. and there are no alarms or lights as you said. i have already had the call where a motor shorted to ground and the supervisor says "the supply is bad, i get 0V phase to ground." Luckily i remembered there is such an animal at a mill i used to work for : 1 phase to ground, no problem. but fix it before the 2nd phase shorts or you will trip the main
 

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Discussion Starter · #17 ·
All I am looking for is someone who is familiar with these configurations to tell me the commonly used trade name for it
 

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Discussion Starter · #18 ·
I’d call it dangerous if you aren’t careful. With that said, it’d be called a floating Star here. Generally speaking when you see them, and I worked at a r-mix co that had three, they are in Delta configuration. The Star configuration gets you a neutral to get a lower single phase voltage for lighting and what not.
so floating is probably the term that i want. I saw it somewhere else in reference to a delta system, but i am trying to verify that through common knowledge of common terminology. It is actually more forgiving than a grounded system, IF you know what it is. The immediate/last ocpd will trip with a short, but it is different to trouble shoot if you dont know what you are working on
 

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Discussion Starter · #19 ·
3 wires leaving the 3 transformers, one wire each transformer. about a 20 foot drop to the first weatherhead/mast down to the feed to the MCC. no ground wire, no neutral wire, just 3 hots going to the mill
Bye the way, believe it or not there is one 30 amp disconnect, single phase, feeding overhead liting. Dont ask me, I dont know how it is working either, other than earth path back to the service entry
 

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3 wires leaving the 3 transformers, one wire each transformer. about a 20 foot drop to the first weatherhead/mast down to the feed to the MCC. no ground wire, no neutral wire, just 3 hots going to the mill
This is the pole transformers that you are mentioning?? From the utilities??
If yes.
The Center tap does it have a bare conductor to the shell with a taped conductor/that circular runs behind the pole transformer to attach to a lower common wire, per transformer?
 
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