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#63103 - 03/06/06 04:45 PM secondary neutral
circuit man Offline
Member

Registered: 11/05/01
Posts: 287
Loc: saluda,s.c.
ok here is one that really has me puzzled.you have a 3 phase 14400 volt primary with no neutral.you feed a single phase dual bushing 7.2/14.4 pri to 120/240 secondary transformer. where do you get the system neutral? i know that the secondary has a midpoint & is also grounded to the can & pole. but what keeps this in line so to speak? THANKS!

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#63104 - 03/06/06 05:03 PM Re: secondary neutral
e57 Offline
Member

Registered: 05/27/03
Posts: 2837
Loc: S.F.,CA USA
"i know that the secondary has a midpoint & is also grounded to the can & pole."
You answered your own question....

"but what keeps this in line so to speak?"
From floating nuetral? There could be some float due to sever phase unbalace, but not by much.
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#63105 - 03/06/06 09:48 PM Re: secondary neutral
wa2ise Offline
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Registered: 11/29/02
Posts: 773
Loc: Oradell NJ USA
It doesn't really matter what the primary side is doing. But all you really want and need is good grounding of your neutral on the secondary side. That gets done at the pole, and also all the service entrances.

If the secondary wasn't tied to ground, capacitive coupling thru the transformer to the primary would create a substantial fraction of the primary voltage to appear on the secondary. Relatively high impedance, but more than enough to electrocute someone.

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#63106 - 03/08/06 01:09 AM Re: secondary neutral
pauluk Offline
Member

Registered: 08/11/01
Posts: 7693
Loc: Norfolk, England
Different voltage levels, but that's how all our transformers are wired in England, as we never have a neutral distributed with the HV lines.

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#63107 - 03/08/06 08:36 AM Re: secondary neutral
Radar Offline
Member

Registered: 04/30/04
Posts: 349
Loc: Los Angeles, CA
Quote:
where do you get the system neutral? . . . i know that the secondary has a midpoint & is also grounded

The grounded mid-point is your neutral, by definition. No (intended) connection between the primary and the secondary electrical systems.

Radar
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