Voltage regualtor voltage shift

[Mbrooke]

So, here is the case. A large 3 phase customer is at the end of a 3 phase circuit. Midline 32 step voltage regulators are present. Because of the neutral shift phase to phase is not phase to neutral and motors are taking a huge hit.




Would changing the pad mounts from a wye-wye to a delta-wye help?

 

[waross]

You could float a wye:delta transformer bank on the downstream side of the voltage regulators. The delta voltage is unimportant. This will react to the neutral shift by developing enough neutral current to offset most of the phase shift. The bank must be large enough to safely pass enough current to cancel the existing neutral current. Search this site for some idea of the upstream problems that a wye:delta bank may introduce. You may consider reverse power detection on each line to open the delta in the event of a back feed.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[Mbrooke]

Wouldn't it be a wye grounded bank instead of floating?

 

[waross]

Sorry for the misunderstanding. My fault. By floating I meant just riding on the distribution circuit with no load.
The wye must be connected to the neutral/ground conductor.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[Mbrooke]

Thanks! I have never tried or thought of that.


So far these are the 2 options and of course yours is another that will be looked into.

1. Change the pad to a delta wye.

2. Replace the old voltage regulators from wye to open or closed delta.(plugging in the calcs this looks like the most attractive solution for now)


As for the bank, 2 questions are in my mind:

A. How would you go about computing the KVA rating?

B. What type of protection is normally used for an intentional star (zero sequence)point? Id imagine a fault would cause one of the fuses to blow.