120/240 with a neutral.

[mn_voyageur]

Is it possible for a panel to be sub-fed 120/240 3P with a neutral.

Service to the building is 120/208 3P. The voltage was then increased to 277/480 3P. The 277/480 was then dropped to 120/240 3P. The 120/240 panel has both a neutral and a ground bar.

 

[don_resqcapt19]

Re: 120/240 with a neutral.

If it is 120/124 three phase with a grounded conductor, then it is a "high leg" delta. If this is the case, B phase should read ~208 volts to the neutral and cannot be used for 120 volt loads.
Don

 

[mn_voyageur]

Re: 120/240 with a neutral.

No high leg.

A?-Neu. 120 VAC
B?-Neu. 120 VAC
C?-Neu. 120 VAC

A?-B? 240 VAC
B?-C? 240 VAC
A?-C? 240 VAC

 

[charlie]

Re: 120/240 with a neutral.

Get your meter tested or purchase a new one. That voltage configuration does not exist.

 

[roger]

Re: 120/240 with a neutral.

Are you sure about the phase to phase voltages, they should be reading around 208 and this would be a WYE connection.


Roger

 

[jbfan74]

Re: 120/240 with a neutral.

I think if you read his post the way I did, 120/208 incoming, then stepped up to 277/480, then stepped back down to 120/240. If that is the case then his voltage readings are correct, or am I reading it wrong?

 

[Ed MacLaren]

Re: 120/240 with a neutral.

then stepped back down to 120/240. If that is the case then his voltage readings are correct, or am I reading it wrong?

How could he get those voltages without a "high leg", in other words, from any other connection except a 4-wire delta?

Ed

 

[steve66]

Re: 120/240 with a neutral.

Would this be possible with 3 single phase 120/240V transformers, each center tapped, with all the center taps connected? Picture Ed's drawing with a center tap on every winding all connected.

Or picture the same thing with only two transformers, like an open delta?

Unusual, but possible? Ok, I grasping for straws here, but maybe it is a high impedence ground?

Steve

[ January 28, 2005, 12:45 PM: Message edited by: steve66 ]

 

[clayton]

Re: 120/240 with a neutral.

how do you get a 240v/120v to neutral system??

three phase?

say starting from a 4160 substation breaker?

 

[Ed MacLaren]

Re: 120/240 with a neutral.

how do you get a 240v/120v to neutral system?? three phase?
say starting from a 4160 substation breaker?

With the 4-wire delta secondary illustrated above.
The primary (not shown) would have to be rated 4160 delta, or 4160/2400 wye.

Ed

 

[crossman]

Re: 120/240 with a neutral.

Originally posted by steve66:
Would this be possible with 3 single phase 120/240V transformers, each center tapped, with all the center taps connected? Picture Ed's drawing with a center tap on every winding all connected.

The multiple center taps would be short circuits the way I see it.

 

[Ed MacLaren]

Re: 120/240 with a neutral.

The multiple center taps would be short circuits the way I see it.

I agree.

Ed

 

[pushpins]

Re: 120/240 with a neutral.

We wired a church that was i20/240 3ph With a HIGH leg. The new service is 277/480 3ph. We connected a bank of transformers 480v 3ph to get 120/240v with a HIGH leg for the original buildings. Strange but it can be done. I saved the handmade drawing I wired it by in 1977.

 

[roger]

Re: 120/240 with a neutral.

Pushpins, welcome to the forum.

To build a Delta configuration with two or three windings is not strange at all, it is infact quite common, although not in the field as you did.

If we center tap one of the windings we will allways have a High leg as you stated.

This would not be what the OP had, given his Phase to Grounded Conductor and Phase to Phase voltages.

Roger