TY - JOUR
T1 - Modeling of heat generated on stress grading coatings of motors fed by multilevel drives
AU - Espino-Cortés, F. P.
AU - Gómez, P.
AU - Betanzos Ramírez, J. D.
N1 - Funding Information:
The authors would like to express their appreciation to the financial support provided by the National Polytechnic Institute and CONACyT in Mexico City.
PY - 2011/8
Y1 - 2011/8
N2 - Stress grading (SG) coatings used in high voltage rotating machines are considerably affected when the machines are controlled by adjustable speed drives. In some applications the SG coatings are subjected not only to voltage components of high frequency associated with the switching devices used by the drive but also to a component of the fundamental frequency above 100 Hz. In this work, the heat generated on SG coatings under multi-level PWM waveforms is studied. The effect of the fundamental frequency, rise time, switching frequency and number of voltage levels, on the resistive heat generation is computed by using a circuit model implemented in PSCAD/EMTDC, which takes into account the nonlinear behavior of the material. According to the results, with a PWM waveform, the average heat density increases with the fundamental frequency, but this increment is considerably smaller than that expected with a pure sinusoidal waveform. Also the simulation results show how a reduction of the average resistive heat in the stress grading coating can be expected as the rise time of the pulses is increased by means of a suitable dV/dt filter. However, the effect of changes on the fundamental frequency or rise time of the pulses on the average heat is less significant compared to the changes in the switching frequency, one of the features of more influence on the heat generation. An increment in the number of levels of the PWM waveform produces a significant reduction in the average heat. With a 5 level configuration the resistive heating becomes similar in magnitude and distribution to the one produced by a pure sinusoidal voltage waveform.
AB - Stress grading (SG) coatings used in high voltage rotating machines are considerably affected when the machines are controlled by adjustable speed drives. In some applications the SG coatings are subjected not only to voltage components of high frequency associated with the switching devices used by the drive but also to a component of the fundamental frequency above 100 Hz. In this work, the heat generated on SG coatings under multi-level PWM waveforms is studied. The effect of the fundamental frequency, rise time, switching frequency and number of voltage levels, on the resistive heat generation is computed by using a circuit model implemented in PSCAD/EMTDC, which takes into account the nonlinear behavior of the material. According to the results, with a PWM waveform, the average heat density increases with the fundamental frequency, but this increment is considerably smaller than that expected with a pure sinusoidal waveform. Also the simulation results show how a reduction of the average resistive heat in the stress grading coating can be expected as the rise time of the pulses is increased by means of a suitable dV/dt filter. However, the effect of changes on the fundamental frequency or rise time of the pulses on the average heat is less significant compared to the changes in the switching frequency, one of the features of more influence on the heat generation. An increment in the number of levels of the PWM waveform produces a significant reduction in the average heat. With a 5 level configuration the resistive heating becomes similar in magnitude and distribution to the one produced by a pure sinusoidal voltage waveform.
KW - insulation
KW - motor
KW - pulse width modulation
KW - stress grading coating
KW - variable speed drives
UR - http://www.scopus.com/inward/record.url?scp=80051711558&partnerID=8YFLogxK
U2 - 10.1109/TDEI.2011.5976135
DO - 10.1109/TDEI.2011.5976135
M3 - Artículo
SN - 1070-9878
VL - 18
SP - 1328
EP - 1333
JO - IEEE Transactions on Dielectrics and Electrical Insulation
JF - IEEE Transactions on Dielectrics and Electrical Insulation
IS - 4
M1 - 5976135
ER -