Neutral Compensator: Learn More About It

[Sidharrth.N]

I have learned from some source that there is a device called neutral compensator .Iwould like to know about it in detail.

 

[negitron]

It's special type of polyphase transformer (usually three-phase) which is wound in such a way as to balance the line phases as much as possible, thereby reducing the neutral current. It's connected on parallel across the load. Its phase-balancing capability also means that if you lose a phase entirely, it will regenerate the missing phase, albeit at a lower voltage than normal.

 

[Bob S]

It's special type of polyphase transformer (usually three-phase) which is wound in such a way as to balance the line phases as much as possible, thereby reducing the neutral current. It's connected on parallel across the load. Its phase-balancing capability also means that if you lose a phase entirely, it will regenerate the missing phase, albeit at a lower voltage than normal.

A while back, I was a postdoc at MIT, and my techician and I accidentally discovered that the grounded 120 V ac outlets in our lab was actually 3 phase 120 V power, ground being the third phase. In discussing this with the utility people, the big transformer powering the building was a 3-phase delta output, and not a wye output, so they chose one of the 3 [STRIKE]wye[/STRIKE] delta legs as ground. In order to balance the load, about 1/3 of the building got each pair of outputs from the transformer [STRIKE]wye[/STRIKE] delta. We were in the 1/3 of the building that got the pair where ground was the third [STRIKE]wye[/STRIKE] delta leg. How could a polyphase transformer correct this problem?

[Edit] three strikes [STRIKE]wye[/STRIKE] delta

 

[negitron]

Good question; that's an...odd setup, to say the least. I'll have to mull it over a bit. What they should have done is use a delta-wye transformer. Any idea why they didn't?

 

[Bob S]

Good question; that's an...odd setup, to say the least. I'll have to mull it over a bit. What they should have done is use a delta-wye transformer. Any idea why they didn't?

Cost too much to replace.

 

[negitron]

Apparently, this is an uncommon, but not unheard-of setup (rare enough that I'm only just finding out about it) known as a http://ecatalog.squared.com/pubs/Electrical%20Distribution/Pressure%20Switches,%20Bolt-Loc/BP/2700DB0202.pdf . As long as everything is balanced and it's wired properly, no corrective action is needed.