closed wye delta to wye wye keeping rotation

[T-Man]

OLD, they use 138.5 secondary tubs to get the 240 volts when they are hooked up wye. the secondary connections in the tub can be connected series or parallel. ours are marked (a, b, c and d.) if you connect (b to c) the result is a series connection and the secondary winding is longer to make 480 wye. if you connect (a to c and b to d) you have a parallel connection which will result in a 240 volt wye connection. I believe Poot is right about deltas on higher voltages causing Ferroresonance. I also think there was concern at the bottom line to have package three phase tubs on some voltages that had to be replaced, when you could store cheaper single phase tubs and just replace the defective one and not store a bunch of high dollar special units in case something happened. which cut down on outage time and costs.

[Old Line Dog]

OLD, they use 138.5 secondary tubs to get the 240 volts when they are hooked up wye. the secondary connections in the tub can be connected series or parallel. ours are marked (a, b, c and d.) if you connect (b to c) the result is a series connection and the secondary winding is longer to make 480 wye. if you connect (a to c and b to d) you have a parallel connection which will result in a 240 volt wye connection. I believe Poot is right about deltas on higher voltages causing Ferroresonance. I also think there was concern at the bottom line to have package three phase tubs on some voltages that had to be replaced, when you could store cheaper single phase tubs and just replace the defective one and not store a bunch of high dollar special units in case something happened. which cut down on outage time and costs.

I guess I just really don't follow ya Ray. "138.5 secondary tubs to get the 240 volts when they are hooked up wye.????" Ya hook up a Wye/Delta Bank...ya get 120/240. And the wing pots can both be a smaller size than the main pot. Ya hook up a Wye/Wye Bank, splt the 3 pots AC/BD...all of the pots are the same size...ya got a 3 phase bank of 120/208, and that siht is inefficient as he$$ with a 240 volt motor. So....I guess I don't understand this....not building wye/delta banks anymore.

[T-Man]

A way to diagram it would be cool. . . .the windings on the secondary of these tubs are 138.5 volts, (not standard 120/240 tubs). you can look at voltage as length. if you connect three of them in a wye, lets say all the H1 bushings are tied and grounded and the H2's are to a phase, the secondary windings are also tied in a wye X1's connected together at a common point and the X3's are the phase legs. when you measure from one secondary X3 winding to another X3, due to Pythagorean theory, (the windings are vectored at 120 degrees), the distance between the secondary windings becomes 240volts. if you series connect the secondary windings in each tub, the length of the secondary winding doubles from X1 to X3, which increases the length to 277 (138.5 +138.5 = 277) and the distance from those X3's become 480.

[Old Line Dog]

A way to diagram it would be cool. . . .the windings on the secondary of these tubs are 138.5 volts, (not standard 120/240 tubs). you can look at voltage as length. if you connect three of them in a wye, lets say all the H1 bushings are tied and grounded and the H2's are to a phase, the secondary windings are also tied in a wye X1's connected together at a common point and the X3's are the phase legs. when you measure from one secondary X3 winding to another X3, due to Pythagorean thermo, (the windings are vectored at 120 degrees), the distance between the secondary windings becomes 240volts. if you series connect the secondary windings in each tub, the length of the secondary winding doubles from X1 to X3, which increases the length to 277 (138.5 +138.5 = 277) and the distance from those X3's become 480.

What EVER you just said...is a "Mystery to me" Fleetwood Mac... https://www.youtube.com/watch?v=Bt-2g9qf0Ds A business that ran on a 3 phase, 120/240 closed delta bank....is LESS Efficient to the customer, when they are put on a 208 Wye/Wye bank. It will cost the customer MORE money on their electric service.

[T-Man]

What EVER you just said...is a "Mystery to me" Fleetwood Mac... https://www.youtube.com/watch?v=Bt-2g9qf0Ds A business that ran on a 3 phase, 120/240 closed delta bank....is LESS Efficient to the customer, when they are put on a 208 Wye/Wye bank. It will cost the customer MORE money on their electric service.

Your 100% right DOG. . . .But these are two different style transformers. 120/240 wound tubs can make 240 delta or 120/208 wye. What I'm talking about is a 138.5 wound secondary tub, and you can make 240 wye out of those.

[Trouble1]

How many times does it need to be explained? If you put one of these online by itself it would get 138.5/240, not 120/240. You get 138.5 volts to from any high side to neutral in the bank when they are connected.

If it's a 240 volt bank made of 3 120/240's, you will get the same reading(138.5 to ground, but this means nothing) except there is not real reference to ground/neutral.

Exact same service 240v, except one has a real ground reference, and one is just a reading on the meter that means nothing really.

With three 120/240's the 240 bank can run with one accidental ground, with three 138/240's, the service will fault when the first accidental ground is introduced since it is already grounded being a wye bank.

It will stay 240v as far as the customer is concerned so it does not really matter to the customer unless they were running with an accidental ground, which they will have to find after the new wye 240v bank is put online because it will fault.

[rob8210]

That would be the reason why they decided to build nothing but wye banks up here, to reduce the possibility of an accidental ground.

[Old Line Dog]

What do ya do for a customer that wants an Open delta bank? I still don't understand the 138.5 volts. Seems a voltage like that would fry light bulbs, daily. I got a 50 KV URD tub, feedin my house and about 6 others. Just 120/240. "KISS" Keep it Simple Stupid.

[climbsomemore]

What do ya do for a customer that wants an Open delta bank? I still don't understand the 138.5 volts. Seems a voltage like that would fry light bulbs, daily. I got a 50 KV URD tub, feedin my house and about 6 others. Just 120/240. "KISS" Keep it Simple Stupid.

The "customer" doesn't ask for Two transformers vs Three.

A utility or somebody who's PAYING for the pot, Extra Switch and Arrestor and 3rd phase if it's not already there is the only person who cares.

[Old Line Dog]

The "customer" doesn't ask for Two transformers vs Three.

A utility or somebody who's PAYING for the pot, Extra Switch and Arrestor and 3rd phase if it's not already there is the only person who cares.

Mr. Clumsum, I been retired since...2001 bud. I got called back to do Storm work in Ike for 3 weeks, 7 days a week, 16 hrs a day. After that....I really retired!! Sorry bud...maby I was just too simple for ya. There are just SO many different situations that require 3 phase power....I sure didn't mean to imply ANYBODY but the power Company...could make that decision.