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#197906 12/29/10 10:04 AM
Joined: Jul 2007
Posts: 265
W
Member
Hi fellas. I am currently installing a machine from China, it came to the US in about 30 crates, and complete with a Chinese electrician to "help" me install it. First, the chinese know nothing about conduit or wireway, he just wants to run wire across the floor to each motor. Second, the machine work sucks, I am not even sure the thing will work when we are through. Now to my question: The voltage in the plant where we are installing this beast is 480Y 277 3 phase 4 wire, and one of the cabinets for controlling a scale needs 480v and 120v inputs. My Chinese helper has said thru his interpeter that in China he could grab one leg of the 480v and the Neutral and have 120v, he then drew it out like a star configuration. Question, is it possible to get 110v out of a 480v star system? I am going pull a 120v feed from another panel, just wondering if this would work as someone said the scale panels were burnt up and had to be repaired while the machine was being run in China. Your thoughts.


Jimmy

Life is tough, Life is tougher when you are stupid
Joined: May 2005
Posts: 984
G
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A 480 Volt Wye (or Star) has 480 Volts between legs and 277 Volts from any leg to neutral.
It sounds like they tried this 'grab one leg and the neutral' stunt and ended up feeding the panel with 277V instead of 110V, thus frying it.

The math works regardless which side of the ocean you're on. The guy seems to have no clue what he's talking about.

I had a somewhat similar situation with a Japanese guy on a machine that I was installing. I could point things out and explain them until I was blue in the face, but he never wavered from his beliefs. If was funny to watch his face when the machine finally ran exactly as designed while I handed him all the 'required' stuff that he insisted was needed.


Ghost307
Joined: Jun 2004
Posts: 1,273
T
Member
Your helper was almost certainly 'sacrificed' by the factory...

That is, he was no use to them and can't possibly give any secrets away.



Tesla
Joined: Nov 2002
Posts: 791
W
Member
Originally Posted by wire_twister
Hi fellas. I am currently installing a machine from China, it came to the US in about 30 crates, and complete with a Chinese electrician to "help" me install it. First, the chinese know nothing about conduit or wireway, he just wants to run wire across the floor to each motor. ...Now to my question: The voltage in the plant where we are installing this beast is 480Y 277 3 phase 4 wire, and one of the cabinets for controlling a scale needs 480v and 120v inputs. My Chinese helper has said thru his interpreter that in China he could grab one leg of the 480v and the Neutral and have 120v, he then drew it out like a star configuration. Question, is it possible to get 110v out of a 480v star system?


The Chinese helper may be wanting to do some temporary wiring as a test lash-up, to satisfy himself and the customer that the equipment did survive shipping and will in fact work. And after that, do a clean professional install. As an EE, I've been there is a sense (delivering and setting up electronic equipment at a customer site many moons ago.

Unless he meant to say "thru a transformer" you can't get 120V from a 480V Y or delta system.

Oh, and China is a 50Hz country. Hopefully, the factory had a 60Hz source, or the equipment won't care about it not being 50Hz and being 60Hz.

Joined: Jul 2007
Posts: 265
W
Member
No, the wiring on the floor was a permanant install, as he showed me a few pictures of installs in China. The drawings of these panels showed the 120v transformer being fed from one line of the 480, and I found and removed this jumper. The motors have all been replaced with 60hz motors so there is no worry there.


Jimmy

Life is tough, Life is tougher when you are stupid

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