B-H characteristic of large power transformers
B-H characteristic of large power transformers
(OP)
For electrical people and transformer experts in this forum,
In general, the complete B-H curve (based on the V-I curve) of large power transformers (above 100MVA) can not measured in manufacture laboratories. This is because of these labs has not anought short-circuit power to saturate deeply large transformers.
Normally, the V-I (B-H) curve is measured in a winding assembled on the ferromagnetic core by supplying voltage up to 120% of the transformer nominal voltage. After that, it is measured the V-I (B-H) curve in the same winding without the ferromagnetic core (air core reactance) and then these two curves are joined graphically.
My questions are:
1) At which point these two curves should be joined?
2) Could that point be considered as the "knee point" of the B-H curve?
These questions heve been posted to magnetic people as well.
Best regards,
Herivelto Bronzeado
In general, the complete B-H curve (based on the V-I curve) of large power transformers (above 100MVA) can not measured in manufacture laboratories. This is because of these labs has not anought short-circuit power to saturate deeply large transformers.
Normally, the V-I (B-H) curve is measured in a winding assembled on the ferromagnetic core by supplying voltage up to 120% of the transformer nominal voltage. After that, it is measured the V-I (B-H) curve in the same winding without the ferromagnetic core (air core reactance) and then these two curves are joined graphically.
My questions are:
1) At which point these two curves should be joined?
2) Could that point be considered as the "knee point" of the B-H curve?
These questions heve been posted to magnetic people as well.
Best regards,
Herivelto Bronzeado






RE: B-H characteristic of large power transformers
Muthu
www.edison.co.in
RE: B-H characteristic of large power transformers
RE: B-H characteristic of large power transformers
RE: B-H characteristic of large power transformers
prc, we use to ask for the B-H curve in our transformer type test as we need this curve to study transformer energizing to asses the impact of the inrush current on the power system.
As the B-H curve given by the manufacturer is obtained in a way I described in my first post, I wonder if anybody knows another method or if that method may be considered correct.
hktrial, the manufacturer lab has no sufficient power to saturate a big transformer with ac voltage. At 2 tesla the current is very high, almost a short circit current.
How can I join the two curves at 2 tesla if I do not have this point? Should I extrapolate the points in the curve measured up to 120% of the transformer nominal voltage?
Best regard,
Herivelto Bronzeado
RE: B-H characteristic of large power transformers
I agree that it is a difficult measurement, but it is not a short circuit. The best way is to use the calculated BH curve which should give values up to 2 Tesla's
Use your measured values up to 120% volts to check the calculated values.