PARALLEL TRANSFORMERS - LOAD/IMPEDANCE CALCULATIONS
PARALLEL TRANSFORMERS - LOAD/IMPEDANCE CALCULATIONS
(OP)
I want to parallel two transformers with the same voltage ratios, kva rating, and vector group.
Can anyone tell me how to calculate the load carried by parallel transformers with difference impedances. In this case 5.97 and 6.1 %
What aout transformers with different kva ratings ?
Can anyone tell me how to calculate the load carried by parallel transformers with difference impedances. In this case 5.97 and 6.1 %
What aout transformers with different kva ratings ?






RE: PARALLEL TRANSFORMERS - LOAD/IMPEDANCE CALCULATIONS
Current in A (Ia), in Amps:
Ia = (Il x Na)/(Na + Nb)
Current in B (Ib), in Amps:
Ib = (Il x Nb)/(Na + Nb
Na = kVAa/Vza
Nb = kVAb/Vzb
Il = total load current (in Amps)
kVAa = Transformer A kVA rating (in kVA)
Vza = Transformer A impedance voltage at full load (%)
kVAb = Transformer B kVA rating (in kVA)
Vzb = Transformer B impedance voltage at full load (%)
There is a more complicated formula (with drawings) for transformers with different X/R ratios but it is a bit of a pig to write!
Regards
RE: PARALLEL TRANSFORMERS - LOAD/IMPEDANCE CALCULATIONS
RE: PARALLEL TRANSFORMERS - LOAD/IMPEDANCE CALCULATIONS
For transformers of different kVA, you'll need to convert them to the same kVA
Znew p.u. = (Zold p.u.) x (kVA newbase/ kVA oldbase)
Keep in mind that in paralleling transformers with different impedances that you will need to be aware of circulating currents.
RE: PARALLEL TRANSFORMERS - LOAD/IMPEDANCE CALCULATIONS
The above method is simple and provide sufficient accuracy, particularly if X/R are the same with small deviation otherwise.
See the enclose site for additional info.
http://www.usbr.gov/power/data/fist/fist1~8/1~8_1.htm