Search for: All records

Insulation in electric machines is vital in determining system reliability and lifespan, especially under extreme environmental conditions. With the rapid shift toward More Electric Aircraft (MEA), All Electric Aircraft (AEA), and advanced space missions, electric motor components must perform reliably under low pressures, wide temperature ranges, and exposure to radiation. Magnet wires are central to motor operation, and their insulation must withstand high voltage stress in these demanding conditions. While prior research has predominantly focused on insulation performance under AC or pulse width modulated (PWM) waveforms and partial discharge (PD) behavior, there is a limited understanding of dielectric strength under direct current (DC) stress, particularly at reduced atmospheric pressures. This paper presents an experimental investigation into the DC dielectric strength of three magnet wire types (15 AWG, 18 AWG, and 20 AWG) tested at three pressure levels: 101kPa,80kPa, and 40 kPa. Using a voltage to breakdown with a constant ramp method, the study evaluates the insulation's withstand capacity across wire sizes and environmental pressures. 

Emerging power electronic drives and converters, especially wide bandgap (WBG) technology-based devices, are expected to operate at high voltages and switching frequencies, potentially reaching up to several hundred kHz. These operating conditions pose significant challenges to the reliability of insulation systems in motor windings, which are critical to the longevity and safe operation of electrical machines. This study investigates the impact of high-frequency square wave voltage pulses on the lifetime of motor winding insulation by conducting lifetime tests on twisted pair magnet wire commonly used in electrical machines. The experiments were conducted in the frequency range of 100 kHz to 300 kHz, with rise times of 50 ns and 400 ns (slew rate ranging from 2.4kV/μ s to 19.2kV/μs), to simulate the conditions typical in modern power electronics and inverter-driven systems. The results show that fast rise times and high switching frequencies influence turn-to-turn insulation's aging and breakdown characteristics. The findings highlight the importance of switching frequency and rise time in determining the reliability of insulation systems, offering critical data to enhance the design and performance of electrical machines in the context of high-frequency operation. 

Electrical insulation is the limiting factor that reduces the lifetime of power components. The aging of insulation, which is heavily caused by partial discharges (PDs) and harsh environmental conditions, eventually leads to complete insulation breakdown. The advancement in developing more- and all-electric aircraft is limited by the existing apparatuses that operate at lower voltages. High applied voltage and lower ambient pressure, commonly envisaged in more and all-electric aircraft, pose significant challenges, as their effects on PD activity and space charge accumulation differ, thereby affecting the apparatus's lifetime. To improve the reliability of aircraft electric motors' performance, it is essential to accurately predict the breakdown performance of the magnet wires used as windings in the motors at low-pressure levels. In this article, we investigate the effect of low pressures on the breakdown voltage of magnet wires with insulation Type I. 

This study examines how fast rise times, which are common in modern power electronics and drive systems, affect the aging of electric machine windings. It focuses on how to ensure these windings can last longer and work reliably in electrical systems. A twisted pair magnet wire with insulation commonly used in wound machines was used to get experimental data to understand how different voltage waveforms can influence endurance testing of motor insulation systems powered by inverters. Unlike past studies that looked at comparatively slower rise times and fewer repetitions, this research specifically addresses the challenges posed by next-generation wide bandgap (WBG)-based conversion systems. These systems operate at very high speeds, up to 100 kV/μs, and switch frequencies up to 500 kHz, where both frequency and rise time are crucial factors affecting insulation aging over time. 

Emerging power electronic drives and converters are planned to operate at high voltages with high switching frequencies (up to a few hundred kHz), which will affect the reliability of insulation systems of windings of electrical machines. To evaluate the insulation quality under such high-frequency pulses, lifetime test is a prominent way. For simplification of test procedure, turn-to-turn insulation samples are approved by IEC 60034-18-42. In past studies, the impact of switching frequencies has been investigated under lower frequencies (up to 20 kHz), which cannot address the challenges of next-generation wide bandgap (WBG)-based power converters. In this study, the lifetimes of turn-to-turn insulations under high switching frequencies (50 kHz) are tested at four different rise times (50 ns, 100 ns, 150 ns, 200 ns), and the impact of switching frequency on the lifetime of the insulation is analyzed.