Current on each phase of a T-T transformer

[gar]

190527-1246 EDT

mbrooke:

Open delta refers to the source, not the load. The T-T transformer is a load. The source to the T-T transformer can be any of wye (neutral not used, essentially a delta), an open delta, or a closed delta.

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[mbrooke]

190527-1246 EDT

mbrooke:

Open delta refers to the source, not the load. The T-T transformer is a load. The source to the T-T transformer can be any of wye (neutral not used, essentially a delta), an open delta, or a closed delta.

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I know, but I am referring to the transformer itself. It looks like an open delta- even though it doesn't function that way.

 

[gar]

190527-1334 EDT

mbrooke:

An open delta has one secondary between A and C and generally with a center tap. While the other secondary is A and B, xor C and B.

Both an open delta and closed delta to a large extent retain the input phase angles of the source to the output. There are only small variations in phase angle that result from the internal impedances and loads.

Whereas the Scott T starts with a 3 phase source and generates two output single phases sources related by 90 degrees rather than three single phase sources related bt 120 degrees.

When you feed a reversed Scott T from a forward Scott T with appropriate connections you can get the equivalent of a three phase transformer.

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[iceworm]

I know, but I am referring to the transformer itself. It looks like an open delta- even though it doesn't function that way.

190527-1334 EDT

mbrooke:

An open delta has one secondary between A and C and generally with a center tap. While the other secondary is A and B, xor C and B.

Both an open delta and closed delta to a large extent retain the input phase angles of the source to the output. There are only small variations in phase angle that result from the internal impedances and loads.

Whereas the Scott T starts with a 3 phase source and generates two output single phases sources related by 90 degrees rather than three single phase sources related bt 120 degrees.

When you feed a reversed Scott T from a forward Scott T with appropriate connections you can get the equivalent of a three phase transformer.

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gar -
I think he got it. Really, I do

 

[mbrooke]

gar -
I think he got it. Really, I do

I like having more detail :happyyes: :thumbsup:

 

[Tony S]

190527-0959 EDT

Tony S:

You have drawn a standard Scott T for 3 phase to 2 phase. That which is the first Wiki drawing. The Wiki drawing is better than yours because it provides a somewhat intuitive impression of the phase angle relationships.

I believe that mbooke's original question relates to the second Wiki circuit, 3 phase to 3 phase. It is probably referred to as a T-T because it is really two Scott Ts in series. A different layout of the schematic might make this clearer.

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I find that statement rather offensive.

 

[mbrooke]

I find that statement rather offensive.

As do I. I've always been taught by prominent people to NEVER trust wikipedia.


I've always found it to be a mix of cited material and conjecture to nit it all together.

 

[gar]

190528-0730 EDT

If you take the Wiki 3 phase to 3 phase schematic, and redraw T2 rotated 90 degrees and placed above T1 now the lamination lines portray the direction of the respective phasor lines. This makes it easier to visualize how the primary voltages replicate to the secondary, and their phase angles.

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[kwired]

I know, but I am referring to the transformer itself. It looks like an open delta- even though it doesn't function that way.

At first glance the fact there is what looks like two coils maybe doing this for you? Might even make you think it is two phase. They way it is connected it functions like three coils.

 

[gar]

190528-1324 EDT

kwired:

There are two separate transformers. These transform 3 phase 120 degree input to 2 phase 90 degree output. By the way the secondaries are wound and connected the 2 phase output is converted to a 3 phase delta output. By adding another tap on one secondary a 3 phase wye output can be produced.

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[kwired]

190528-1324 EDT

kwired:

There are two separate transformers. These transform 3 phase 120 degree input to 2 phase 90 degree output. By the way the secondaries are wound and connected the 2 phase output is converted to a 3 phase delta output. By adding another tap on one secondary a 3 phase wye output can be produced.

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My reply was to a comment about it looking like open delta at first glance, with two transformers one kind of may think that at first was all I was saying. But they are connected in a manner that the end result is pretty much same as delta-wye.