Voltage rise rate‐related generalised probabilistic lifetime model of turn‐to‐turn insulation in inverter‐fed motors

Abstract

The lifetime model of turn‐to‐turn insulation in inverter‐fed motors is studied. A lifetime model has been built by considering the effect of inverter‐generated high voltage rise rate (dv/dt up to 20 V/ns). This model is followed by the generalised probabilistic model, in which the lifetime is proportional to the nth power of the voltage rise rate. Moreover, by investigating the effect of voltage rise rate on the partial discharge characteristics, it is found that the effect of voltage rise rate on the charge transport process in a voltage cycle is similar to that of the voltage amplitude. The enhanced partial discharge activity and induced charges are responsible for accelerated ageing and thus determine the final lifetime of turn‐to‐turn insulation. In this case, the generalised probabilistic electric lifetime model is applicable to the voltage rise rate as well as the voltage amplitude.

Correlation between lifetime model of BOPP film and rise rate under nanosecond pulse voltage

“…The range of the rise rate, the fitting parameters and the goodness of fit are given in table 5. As can be seen from figure 11: (1) equation ( 10) not only fits the experimental results in this paper, but also fits the relationship between the solid dielectric lifetime and the rise rate reported in the literature [8][9][10][11][12] equally well (all goodness of fits are greater than 0.93), which further confirms the correctness of the proposed lifetime model; (2) The lifetime power exponent n takes the value between 0-1, with the increase of the rise rate, the lifetime power exponent n does not show a clear pattern of change. (3) The value of parameter C 2 is taken between 1.67 and 2.78, and according to the above analysis, it can be seen that the parameter C 2 is mainly affected by the voltage endurance coefficient m and the breakdown field strength of the solid dielectric E BD .…”

“…where a 2 is constant, and b 2 is the electric field enhancement coefficient From equations ( 7) and ( 8) and figure 9, it can be seen that the relationship between the rise rate and both the electric field and the breakdown voltage can be described by the inverse power model. Combining equations ( 7) and ( 2), the relationship between the dielectric lifetime N L and the rise rate dV/dt can be obtained, as shown in equation (9):…”

“…) n (9) where the lifetime power exponent n = bm, and a is constant, and b is the electric field enhancement coefficient Making a logarithm of both sides of equation (9) gives…”

“…To further verify the correctness of the proposed lifetime model, and to further analyze the effect of the rise rate on the value of the lifetime power exponent n, the experimental data from the literature [8][9][10][11][12] are replotted in a log-log coordinate system, and linearly fitted based on equation (10), as shown in figure 11. The range of the rise rate, the fitting parameters and the goodness of fit are given in table 5.…”

“…However, in the literature that has been reported on the cumulative breakdown of solid dielectrics, the rise rate is mainly a few V ns −1 -tens of V ns −1 level. Literature [8][9][10] reported that the cumulative breakdown characteristics of turn-toturn insulation under impulse voltages with rise rate of 0.7-67.4 V ns −1 , 15-20 V ns −1 , and 39.9-83.4 V ns −1 , respectively. The electrical endurance experiments of polyurethane ware carried out under impulse voltages with rise rate of 4.7-18.8 V ns −1 [11].…”