# 480 Primary 3 phase 240/120 secondary

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#### ArnoldE

##### New member
I have a 480 primary. There are two different transformers. One takes the 480 primary to a 208/120 secondary. The other takes the 480 primary to a 240/120 secondary but the middle leg is 208. Is there a 3 phase transformer that converts the 480 primary to 240/120 with no hi leg?

#### masterinbama

##### Senior Member
Yes, it would be single phase on the secondary though.

#### GoldDigger

##### Moderator
Staff member
Yes, it would be single phase on the secondary though.
And it would work just as well with a 240 single phase input.
Just do not plan on getting three of them, one per phase, and grounding the secondary neutral of each one. That would work, but it would be incredibly confusing (and therefore dangerous) for anyone working with the wiring system later.

And where would you find six-phase panels.

#### augie47

##### Moderator
Staff member
Be cautious, unless things have changed since the last time I was involved with a similar project, a 240/120 secondary has a severe limitation on the neutral load (somewhere in the 5% to 10% of kva rating) Check your manufacturer data.

#### Jraef

##### Moderator
Staff member
Yes, it would be single phase on the secondary though.
Actually, no. If he has 120/240 on the 3 phase secondary somewhere, then there WILL be a "high" leg.

There is no such thing as a 120/240V 3 phase system. In a 3 phase system with a neutral, the line to neutral voltage is always the L-L voltage divided by the sq. rt. of 3 (1.732). So for 3 phase 4 wire where the L-N voltage is 120, then the L-L voltage will be 120 x 1.732, or 208V. You can't write your own laws of physics.

#### ActionDave

##### Chief Moderator
Staff member
Actually, no. If he has 120/240 on the 3 phase secondary somewhere, then there WILL be a "high" leg.

There is no such thing as a 120/240V 3 phase system. In a 3 phase system with a neutral, the line to neutral voltage is always the L-L voltage divided by the sq. rt. of 3 (1.732). So for 3 phase 4 wire where the L-N voltage is 120, then the L-L voltage will be 120 x 1.732, or 208V. You can't write your own laws of physics.
Your irrefutable physics run afoul of the new NEC definition of "neutral".

Neutral Point. The common point on a wye-connection in a
polyphase system or midpoint on a single-phase, 3-wire sys-
tem, or midpoint of a single-phase portion of a 3-phase delta
system, or a midpoint of a 3-wire, direct-current system.

I agree with you BTW. And I am as non-technical as one can get.

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