Partial discharge (PD) measurements under repetitive impulse voltages are critical for the qualification of inverter-fed motor insulation systems. Severe electromagnetic interference due to high frequency switching from power electronic devices can cause the traditional PD detection techniques of sinusoidal voltage unfeasible. This article presents the design of an Archimedes spiral antenna that can work effectively for PD detection under fast rise time repetitive impulse voltages. The antenna structure is optimized by a media superstrate with a high dielectric constant over the radiant surface. Through the optimized design, both the gains of the antenna in the 0.5–1.5 GHz frequency range and the signal-to-noise ratio for PD detection are increased substantially. Modeling and experimental results prove that the gain of the antenna can reach 2.5 dB in the frequency range of 500–900 MHz and become higher than 7.0 dB in the frequency range of 900–2.0 GHz, with a voltage standing–wave ratio smaller than 1.4. This seems to be a significant achievement for PD detection under fast rise time impulse voltages.

The improvements in signal-to-noise ratio (SNR) are indispensable to obtain the desired output signal of partial discharge (PD) under square wave pulsewidth modulation (PWM) voltage. In this article, the effect of complex PWM voltage parameters (rise time, fall time, frequency, duty cycle) on the SNR of PD tests is investigated. The results revealed that the sensor's high-frequency gain should be increased to improve the SNR under faster switching. PD impulses are more likely to be submerged in the residual interference under high-frequency voltage. The SNR can be improved by only detecting the PD at the rising front because the PD signal overlaps with commutation noise at the falling front of short duty cycle voltage, such as 0.03% duty cycle. The above results can reference the PWM parameters and improve the SNR in PD tests for rotating machines controlled by power electronics.

The linear-motor type flux pump is a wireless DC power source for high-temperature superconducting coils, which is compact in size, efficient in energy use, fast in output control, etc. It consists of three major parts: DC windings, phase windings and iron circuit, which generates a DC-bias AC travelling wave in its airgap. In theory, there are three controllable parameters such as DC-bias field, amplitude of the AC travelling wave, and the field frequency (travelling speed). By changing those parameters, we change the applied fields and its DC output current into superconducting coils. For studying the impact of those parameters on its DC output, this paper uses a fixed step algorithm to collect the current charging data, by automatically controlling the flux pump device, and then establishes an output database. By using this algorithm, we have searched out the maximum pumped current and analyzed the impact of the three parameters. We have also found out that, in order to get maximum current output, the value of the DC-bias field should be close to the amplitude of AC magnetic field.

The application of wide band-gap power electronic devices brings more challenges to insulating packaging technology. Knowing the influence of applied voltage parameters on insulation performance is helpful to evaluate the insulation condition of electric power equipment. In this paper, the effect of repetitive square wave voltage duty cycle on the growth characteristics of electrical trees in epoxy resin was studied. The experimental results show that the square wave voltage duty cycle has a significant influence on treeing features. The electrical tree proportion initiation has shown a decreasing trend, and the shape of the electrical tree changes from pine-like to branch-like by increasing the duty cycles. The length and damaged area of electrical tree increased with the increase in the duty cycle up to 10% and then decrease by increasing the duty cycle higher than 30%. It indicates that a low duty cycle will enhance the electron injection and accumulate space charges and thus accelerate electrical tree development. Under short duty cycles, the electric field due to the shielding effect near the needle tip suppresses the electrical tree growth, which results in treeing growth stagnation. The obtained results are helpful to keep these parameters in mind during the design of epoxy-based insulation such high-voltage rotating machines and power electronic device packaging.

Variation in air pressure severely affects the insulation of electric vehicle (EV) motors, hence weakening the reliability of EVs for safe operation. Nomex‐polyimide‐Nomex, a typical insulation material for EV motors, was used to investigate the motor insulation performance under different air pressures. The results show that the partial discharge inception voltage is significantly reduced for EV motors operated at lower air pressures, and the probability of partial discharge (PD) occurrence is increased. The macroscopic results reveal that the active area of the PD expands at low pressure, while the non‐corroded ring appears in the centre. Additionally, although the number and amplitude of the PD increase significantly with decrease in air pressure, the active area of the PD expands and electrical stress on the insulation per unit area increases slowly. Therefore, when the pressure decreased from 60 to 40 kPa, the endurance life does not show a significant downward trend. Furthermore, the dielectric constant and loss of the low‐pressure samples significantly change during the ageing process, which further indicates critical degradation of the insulation. The aforementioned investigations reveal that the air pressure at different altitudes has a significant impact on the performance of insulation materials.

The urgent need for the safer operation of inverter-fed motors is leading research to the qualification tests under high frequency rectangular wave voltages. Consequently, the generation of rectangular wave voltages with adjustable parameters has become a major concern for manufacturers and researchers. This article presents a design of high frequency and high voltage pulse generator able to provide unipolar or bipolar pulses up to 20 kV peak-to-peak with variable rise and fall time that can be tuned down to 40 ns. Such a generator is performant enough for testing a large part of motors following standards and with more stressful conditions for research of new winding technologies. Resorting to high voltage push–pull solid-state switches and dielectrics liquid and air-cooling technique, the tested capacitance load can reach up to 3000 pF. Also, the overcurrent protection circuit is carefully designed and verified by using real-time logic control hardware. The proposed generator has been successfully used for endurance tests and partial discharge inception voltage (PDIV) detection at repetitive impulsive voltages for capacitive, inductive insulation structures, and windings during the qualification evaluation of inverter-fed motors.