Another transformer question

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So I have been trying to find a 208 Y \ 480 Y step up transformer. My suppliers are telling me they can only find 208 D \ 480 Y. It seems to me that application can't be rare enough to not even make one. Could it be as simple as feeding the 208 D primary with 208 Y without the neutral?
 
Brand New said:
So I have been trying to find a 208 Y \ 480 Y step up transformer. My suppliers are telling me they can only find 208 D \ 480 Y. It seems to me that application can't be rare enough to not even make one. Could it be as simple as feeding the 208 D primary with 208 Y without the neutral?
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Yes, it really is that simple.
 
As the "end user" of electricity, it is rare for someone to want a Y-Y transformer. They are often limited to voltages above 15 kv and used in applications where there is significant distribution downstream of the transformer.

The Y system on your 208 side doesn't dictate that a Y connection must be used. Smart $ is correct, it's as simple as that.

Jim T
 
The Delta/Wye transformer configurations are refering to how the individual coils (either high side or low side) are interconnected.

A Delta connected high side would have one coil each connected:

A-phase and B-phase
B-phase and C-phase
C-phase and A-phase

If it was Wye connected, each coil would be connected as follows:

A-phase and Neutral
B-phase and Neutral
C-phase and Neutral
 
Many of the 3-phase transformer banks I see around here use single-ended primaries, so the Y primary is not as rare as you might think. I fused cutout per transformer.

(Yeah, I look.)
 
LarryFine said:
Many of the 3-phase transformer banks I see around here use single-ended primaries, so the Y primary is not as rare as you might think. I fused cutout per transformer.

(Yeah, I look.)
Click to expand...

Delta banks also use 1 cutout per phase. Y primaries are common in utility applications, but not in end user installations.

Jim T
 
Why do utilities use a Y primary? Seems like it would be an extra wire to run, though I have seen some systems that run 4 wire everywhere, I often wonder why they do that. I have asked a few linemen, and none of them can ever give me a good reason.

Mike
 
Like Smart said, I think you really want a 208V delta to 480V wye. Just don't use the neutral wire on the 208V side.

If you have some special reason that you really want a wye-wye transformer, you might try to find 3 single phase 208V - 480V transformers. Then just connect the primary's and secondaries in wye configurations.

Steve
 
mhulbert said:
Why do utilities use a Y primary? Seems like it would be an extra wire to run, though I have seen some systems that run 4 wire everywhere, I often wonder why they do that. I have asked a few linemen, and none of them can ever give me a good reason.

Mike
Click to expand...

Wye primaries are safer because of grounding, more reliable because the loss of 1 phase causes outages to only 1/3 of the single phase customers, not 2/3, and often the natural step when utilities first needed to increase capacity.

A 2400 volt delta system was converted to a 2400/4160 wye, with a 173% incrrease in capacity. Similarly 7200 deltas were converted to 7200/12,470 wyes.

There are many other reasons as well.

Jim T
 
Brand New said:
So I have been trying to find a 208 Y \ 480 Y step up transformer. My suppliers are telling me they can only find 208 D \ 480 Y. It seems to me that application can't be rare enough to not even make one. Could it be as simple as feeding the 208 D primary with 208 Y without the neutral?
Click to expand...

It is very typical in a step-up transformer to have the primary side (low voltage in this case) be delta, with the high voltage side connected in wye, with the neutral ground through a resistor, or reactor. Solidly grounded is OK but not prefferred.

There is no need to use a Y/Y.
 
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