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Berglund, R. (2009) *Frequency Dependence of Transformer Losses*. Göteborg : Chalmers University of Technology

** BibTeX **

@mastersthesis{

Berglund2009,

author={Berglund, Ragnar},

title={Frequency Dependence of Transformer Losses},

abstract={In this thesis, theory concerning skin effect, eddy current and magnetic hysteresis in transformers has
been investigated. An electric equivalent model of a transformer based on this theory is proposed. The
validity of this theory and the usefulness of the model have been tested through laboratory
measurements. In these measurements three scenarios where studied: a no load test of a transformer
with varying frequency, a transformer loaded with a diode rectifier and last, the transformer was
loaded with a pulse generating load. The model has been used to perform a prediction of the energy
savings available through the use of amorphous transformer cores, and active filters. Finally a
comparison of the two most widespread down rating standards for transformers has been made.
Analytical calculations suggest that the core impedance of a transformer increases as the square root of
the frequency. A no load test with varying frequency supports this. The analysis also shows that at
high frequencies the resistance of a copper winding increases as the square root of the frequency. The
proposed model proved more accurate at higher frequencies compared to lower frequencies. A
comparison of the European down rating standard with the standard proposed in this report shows that
the two standards behaves similarly for lower frequencies, but that the European standard is stricter for
the higher frequencies. The model suggests that the use of amorphous steel in the transformer core
decreases the core losses by 48% using assumptions stated in the report; the model also shows that the
use of amorphous steel decreases the losses that are generated by load harmonics by 8%.},

publisher={Institutionen för energi och miljö, Elteknik, Chalmers tekniska högskola},

place={Göteborg},

year={2009},

note={80},

}

** RefWorks **

RT Generic

SR Print

ID 105374

A1 Berglund, Ragnar

T1 Frequency Dependence of Transformer Losses

YR 2009

AB In this thesis, theory concerning skin effect, eddy current and magnetic hysteresis in transformers has
been investigated. An electric equivalent model of a transformer based on this theory is proposed. The
validity of this theory and the usefulness of the model have been tested through laboratory
measurements. In these measurements three scenarios where studied: a no load test of a transformer
with varying frequency, a transformer loaded with a diode rectifier and last, the transformer was
loaded with a pulse generating load. The model has been used to perform a prediction of the energy
savings available through the use of amorphous transformer cores, and active filters. Finally a
comparison of the two most widespread down rating standards for transformers has been made.
Analytical calculations suggest that the core impedance of a transformer increases as the square root of
the frequency. A no load test with varying frequency supports this. The analysis also shows that at
high frequencies the resistance of a copper winding increases as the square root of the frequency. The
proposed model proved more accurate at higher frequencies compared to lower frequencies. A
comparison of the European down rating standard with the standard proposed in this report shows that
the two standards behaves similarly for lower frequencies, but that the European standard is stricter for
the higher frequencies. The model suggests that the use of amorphous steel in the transformer core
decreases the core losses by 48% using assumptions stated in the report; the model also shows that the
use of amorphous steel decreases the losses that are generated by load harmonics by 8%.

PB Institutionen för energi och miljö, Elteknik, Chalmers tekniska högskola,

LA eng

OL 30