Connecting 3 phase Transformers
Connecting 3 phase Transformers
(OP)
what happens if a the H1 and H3 phases are connected backwards in a 3 phase delta - wye transformer.
When was the last time you drove down the highway without seeing a commercial truck hauling goods?
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Connecting 3 phase Transformers
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RE: Connecting 3 phase Transformers
RE: Connecting 3 phase Transformers
RE: Connecting 3 phase Transformers
What you describe as 'telescoped' windings usually indicates an internal fault.
Can you explain what was done a little better?
RE: Connecting 3 phase Transformers
RE: Connecting 3 phase Transformers
RE: Connecting 3 phase Transformers
RE: Connecting 3 phase Transformers
The nameplate of a delta-wye transformer will show the vector diagram for the H1, H2, H3, and X0, X1, X2, & X3 connections.
I don't know what the unit stickers are.
Again, just swapping the H cables around on the H terminals will not cause a fault. (Swapping any H to X leads will!)
When you say it immediately shut down, I'm assuming a C/B or a fuse opened, and there was some noise/arcing in the transformer, etc?
Can you explain "the taps in the other two windings seem to have hardwired themselves in its maximum setting" better? Usually, a transformer will have five taps (one for nominal voltage, two above and two below nominal)which are adjustable for each coil by means of a jumper wire. What size transformer and what voltages are we dealing with?
RE: Connecting 3 phase Transformers
RE: Connecting 3 phase Transformers
1. Phase sequence will be opposite. (Motors will run opposite direction)
2. Phase shift between primary and secondary will be reversed. So if you have a standard ANSI transformer, where the low side lags the high by 30 deg, swapping inputs to H1 and H3 will result in low side leading the high side by 30 deg.
The phasor diagram on the nameplate is based on a normal positive phase sequence being connected to H1-H2-H3. If you reverse the input, the phase shift will be in the opposite direction from what is shown on the nameplate.
So if you attempted to parallel this transformer with another transformer connected differently, things would be very exciting for a few cycles.
There may have been a phase sequence relay that tripped when H1 and H3 were swapped.
RE: Connecting 3 phase Transformers
I ad a transformer with a rising level of combustible gases. We pulled it and sent it ou for rework. When it came back, we did the standard battery of tests, including turns ratio test.
Running the turns ratio test, we found things NOT working right. Investigation revealed that the nameplate showed X0-X1-X2-X3, and that's the way the hard bus on the secondary was connected. However, the rebuild came back with x1-x2-x3-x0. The transformer went back on the truck and back to the service center for a fix.
old field guy
RE: Connecting 3 phase Transformers