Three phase transformer vector groups
Three phase transformer vector groups
(OP)
I wanted to demonstrate the voltage phase shift between primary and secondary on a three phase transformer so I had one built by a local company. All the winding ends are accessible so I can configure it any way I please.
When connected up as star-star I expected there to be no phase shift but using an oscilloscope I observed a difference of around 1mS between primary and secondary voltages on the same phase. (I say 1mS but it is difficult to be exact and it could be anything between 0.5 to 1mS)
To double check I configured the transformer as delta-delta but still observed the same 1mS difference.
Am I missing something here? surely there should be no phase difference between primary and secondary voltages when configured in this way. Or will there always be a small difference due to the limitations of this transformer.
Thanks
When connected up as star-star I expected there to be no phase shift but using an oscilloscope I observed a difference of around 1mS between primary and secondary voltages on the same phase. (I say 1mS but it is difficult to be exact and it could be anything between 0.5 to 1mS)
To double check I configured the transformer as delta-delta but still observed the same 1mS difference.
Am I missing something here? surely there should be no phase difference between primary and secondary voltages when configured in this way. Or will there always be a small difference due to the limitations of this transformer.
Thanks






RE: Three phase transformer vector groups
The 'T' network is a fairly good representation although there are equivalent Π networks and slightly simpler 'L' networks also in common use. The small phase shift is due to the series leakage reactance of the transformer.
RE: Three phase transformer vector groups
Test unloaded. It doesn't take much load to swamp out this effect.
(The d'Arsonval movement responded to average values of voltage which were scaled to RMS values. The readings from line to line and from line to neutral would no longer be in the ratio of 1.73:1)
Bill
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"Why not the best?"
Jimmy Carter
RE: Three phase transformer vector groups