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Dear Sir,
We have tested a 690v (3ph)/230 (1ph) 5KVA Transformer in our company. We had tested the voltage changes in the secondary winding (230V) by removing the supply of the one phase in the primary. The result is given below...
Primary Secondary
****************************************
1.Removed R Phase 195V
2.Removed Y Phase 25V
3.Removed B Phase 195V
The secondary voltage is only 25V when we are removing the Y phase... what may be the reason? Any idea?
R - Y and B - Y, so when you remove the Y phase the circut is through 2 coils in series from R - B. Are there any capacitors in the circuit?
Regards,
Roy
If you put a scope on the 3 signals you will see that the 2 phases are not truly 120 degrees apart from each other.
Check voltage to ground also as it is common to do this with a center tied to ground.
o Two single-phase transformers.
o Three single-phase transformers.
o A single 3-phase transformer, D-d or Y-d
However, success with any of the arrangements listed above is very dependent on the leakage reactances of the transformer, core-construction, the ability to reverse individual coil polarity, and access to the terminal-pairs associated with individual primary and secondary coils.
If you want additional detail, please provide:
a) The primary and secondary currents for the conditions you outlined!
b) If possible, the number of leads involved!
c) The approximate size of the enclosure!
d) Confirmation that the secondary is a sine-wave?
Regards, Phil Corso (cepsicon@aol.com)
On Apr 26, 2008 11:49 pm, Ranjith wrote:
We have tested a 690v (3ph)/230 (1ph) 5KVA Transformer in our company. We had tested the voltage changes in the secondary winding (230V) by removing the supply of the one phase in the primary. The result is given below...
Primary Secondary
****************************************
1.Removed R Phase 195V
2.Removed Y Phase 25V
3.Removed B Phase 195V
The secondary voltage is only 25V when we are removing the Y phase... what may be the reason? Any idea?
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