Insulation Aging Mechanisms in Inverter-Fed Electrical Machines

In modern electrical drives, inverter-fed machines are subject to rapidly switching voltages with high dv/dt and overvoltage reflections. This arises from pulse width modulation techniques employing wide-bandgap semiconductors such as SiC or GaN. The resulting steep voltage transitions impose non-uniform electric field distributions across the stator winding insulation, promoting localised stress intensification and initiating partial discharges within microscopic voids or material defects. Repetitive PD activity leads to cumulative erosion of polymeric materials, treeing phenomena and progressive loss of dielectric strength. Concurrently, space charge accumulation under pulsed fields can distort the internal field profile, accelerating chemical degradation and thermal ageing. Environmental factors including temperature, humidity and operating pressure further influence PD inception and propagation, while dielectric heating from high-frequency losses exacerbates thermal breakdown. Over prolonged operation, these mechanisms collectively reduce the residual lifespan of motor insulation, potentially resulting in turn-to-turn or turn-to-ground faults. To mitigate these effects, novel insulation systems and monitoring techniques have been developed that integrate advanced materials, tailored impregnation processes and diagnostic criteria based on PD pattern recognition, enabling early detection of incipient ageing and informed maintenance scheduling.

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Insulation Aging Mechanisms in Inverter-Fed Electrical Machines publication trend

The graph below shows the total number of articles in insulation aging mechanisms in inverter-fed electrical machines across all publications each year (not limited to Nature Index journals).

Technical terms

Partial Discharge (PD): Localised, partial breakdown of insulation in voids or defects without full electrical conduction.

Dielectric Breakdown: Irreversible transition of an insulating material to a conductive state under excessive electric stress.

Space Charge: Net accumulation of electric charges within an insulating medium that distorts internal field distribution.

Pulse Width Modulation (PWM): Technique for controlling inverter output voltage by varying the duration of successive voltage pulses.

Wide-Bandgap Semiconductor: Material such as silicon carbide or gallium nitride offering high switching speed and voltage capability.

References

1. A review on insulation challenges towards electrification of aircraft. High Voltage (2023).
2. The Insulation Resilience of Inverter-Fed Low Voltage Traction Machines: Review, Challenges, and Opportunities. IEEE Access (2022).
3. The Challenges of Reliable Dielectrics in Modern Aerospace Applications: The Hazard of Corona Resistant Materials. IEEE Transactions on Transportation Electrification (2022).
4. Impact of PWM Voltage Waveforms on Magnet Wire Insulation Partial Discharge in SiC-Based Motor Drives. IEEE Access (2021).
5. Effects of Environmental Factors on Partial Discharge Activity and Estimation of Insulation Lifetime in Electrical Machines. IEEE Access (2020).