Partial discharge characteristics of interturn insulation used for inverter-fed traction motor under bipolar impulses

Inverter-fed traction motors, which are employed for electric-multiple-units (EMUs), are subjected to Pulse Width Modulated (PWM) impulse voltage. Impulse voltage has fast rise/fall time and high repetition frequency. The failure mechanism of insulation under impulses is different from that of standard 50 Hz sinusoidal condition. Partial discharge (PD) characteristics (discharge number, mean discharge quantity and phase resolved partial discharge (PRPD) pattern) with different frequencies and different rise times of impulse voltage were investigated. The results reveal that discharge number and mean discharge quantity increase, while PRPD pattern moves to the zero of impulse voltage with decrease of rise time. Discharge number and PRPD pattern follow that trend with increase of frequency, the value of mean discharge quantity is similar. Memory effect of the deposited space charges on PD was studied. PRPD pattern moves to the zero of bipolar impulse voltage due to the role of space charges, with increase of frequency and decrease of rise time. It is revealed that available discharge time is prolonged and overvoltage across the cavity increases with augment of frequency, which results in discharge number increasing. Under the condition of shortening the rise time, with the same statistical time lag tL, ∆V would increase if dV/dt is higher, which results in enhancement of discharge quantity. Discharge number increases with reduction of rise time, because the decreased multiple of td is lower than the increased multiple of dV/dt. Study of PD characteristics and role of space charges is helpful to the exploration of the destructive mechanism of insulating materials under bipolar impulse. partial discharges, bipolar impulse, interturn insulation, electric-multiple-units, memory effect, space charges

[1]  R. Bartnikas,et al.  On the character of different forms of partial discharge and their related terminologies , 1993 .

[2]  Gian Carlo Montanari,et al.  Modeling memory phenomena for partial discharge processes in insulation cavities , 2003, 2003 Annual Report Conference on Electrical Insulation and Dielectric Phenomena.

[3]  N. Fujimoto,et al.  Partial discharge. XV. Improved PD testing of solid dielectrics using X-ray induced discharge initiation , 1992, IEEE Electrical Insulation Magazine.

[4]  Massimo Lazzaroni,et al.  PD recurrence in cavities at different energizing methods , 2004, IEEE Transactions on Instrumentation and Measurement.

[5]  Qiang Gao,et al.  Position Estimation of AC Machines Over a Wide Frequency Range Based on Space Vector PWM Excitation , 2007, IEEE Transactions on Industry Applications.

[6]  K. Zhou,et al.  Microscopic view of aging mechanism of polyimide film under pulse voltage in presence of partial discharge , 2010, IEEE Transactions on Dielectrics and Electrical Insulation.

[7]  R. Bodega,et al.  The effect of voltage frequency on partial discharge activity , 2002, Annual Report Conference on Electrical Insulation and Dielectric Phenomena.

[8]  Gian Carlo Montanari.  IEC 61934: Electrical measurements of partial discharges during short risetime repetitive voltage impulses , 2006 .

[9]  Matthias Berth,et al.  Electrical stress and failure mechanism of the winding insulation in PWM-inverter-fed low-voltage induction motors , 2000, IEEE Trans. Ind. Electron..

[10]  T. Tanaka.  Partial discharge pulse distribution pattern analysis , 1995 .

[11]  Weijun Yin,et al.  Dielectric properties of an improved magnet wire for inverter-fed motors , 1997 .

[12]  Gary L. Skibinski,et al.  Effect of surge voltage risetime on the insulation of low voltage machines fed by PWM converters , 1997, IAS '97. Conference Record of the 1997 IEEE Industry Applications Conference Thirty-Second IAS Annual Meeting.

[13]  Graham Williams,et al.  Conference on Electrical Insulation and Dielectric Phenomena , 1982, IEEE Transactions on Electrical Insulation.

[14]  M. Nakaoka,et al.  Advanced control of PWM converter with variable-speed induction generator , 2006, IEEE Transactions on Industry Applications.

[15]  D. Fabiani,et al.  Relation between space charge accumulation and partial discharge activity in enameled wires under PWM-like voltage waveforms , 2004, IEEE Transactions on Dielectrics and Electrical Insulation.

[16]  G. Mazzanti,et al.  First electron availability and partial discharge generation in insulation cavities: effect of light irradiation , 2005, IEEE Transactions on Dielectrics and Electrical Insulation.

[17]  Davide Fabiani,et al.  Aging acceleration of insulating materials for electrical machine windings supplied by PWM in the presence and in the absence of partial discharges , 2001, ICSD'01. Proceedings of the 20001 IEEE 7th International Conference on Solid Dielectrics (Cat. No.01CH37117).

[19]  P. Morshuis,et al.  Partial discharges at DC voltage: their mechanism, detection and analysis , 2005, IEEE Transactions on Dielectrics and Electrical Insulation.