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I’m having a brain fart. Is this transformer delta/delta?

WVHick

Plastic
Joined
Dec 2, 2018
The new acme model number for this transformer is delta/delta but this one doesn’t specifically say. I keep having a brain fart but the windings look weird to me.

820347C8-5FF3-4196-8175-E601F0D203A1.jpg
 
It is effectively delta-delta, yes.

The actual internal wiring is like a high leg 3 phase, but the center tap is not brought out. So the only connection options are as delta-delta.

There is no option for a ground on the secondary, other than a corner ground.
 
It is effectively delta-delta, yes.

The actual internal wiring is like a high leg 3 phase, but the center tap is not brought out. So the only connection options are as delta-delta.

There is no option for a ground on the secondary, other than a corner ground.

Great thanks. So I can just come off H1, H2, H3 straight into my 480V delta motor, correct?
 
The new acme model number for this transformer is delta/delta but this one doesn’t specifically say. I keep having a brain fart but the windings look weird to me.

View attachment 325485

They only "look weird" because (s)he who drew it optimized use of "presentation space" to get readability onto a smaller label!

Re-draw it yerself - on nested triangles rather than stacked rectangles - initially leaving off the taps ... and see it as the classical Delta-Delta.

Then add the taps... and it should make perfect sense.
 
Agreed, that's a dumb drawing. Some engineer felt the need to justify their existence by taking something well-established and making it needlessly complicated.

So complicated in fact that I nearly didn't notice that what you have appears to be a "Scott - T" transformer, not a delta-delta. Used for converting two phase to three phase and vise-versa - though yours appears to lack the connections needed for that. I believe the technical term for what you have is an 'odd duck'.

Notice the vector diagram in the bottom right.

Interesting find.

As far as secondary grounding, you're looking at either a corner ground or a separate 'zig-zag' transformer (unlikely as those are usually for impedance-grounded systems).
 








 
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