Thermal Overload and Insulation Aging of Short Duty Cycle, Aerospace Motors

TLDR

Electrical machines for transportation, especially aerospace, must be highly reliable and possess high torque density due to weight constraints, yet insulation overheating can shorten lifetime and compromise reliability. The study experimentally investigates how short‑time thermal overload affects insulation lifetime in low‑voltage, randomly wound electrical machines. The authors aged round enameled magnet wire coils with accelerated thermal cycles, measured insulation degradation, and statistically processed the data with a two‑parameter Weibull distribution to build a lifetime prediction model used to estimate motor lifetime in an aerospace electromechanical actuator. The experimental data analysis yields a Weibull‑based lifetime prediction model for insulation under short‑time thermal overload.

Abstract

Electrical machines for transportation applications need to be highly reliable, particularly if they drive safety-critical systems. At the same time, another main requirement is represented by the significant torque density, especially for aerospace, where weight constraints are extremely stringent. For achieving high peak torque, an effective strategy consists in supplying the windings with a current greater than the rated value; thus, thermally overloading the machine for limited time periods. However, if the insulation is overheated, the machine lifetime is shortened and reliability issues can arise. This paper experimentally investigates the influence of short-time thermal overload on the insulation lifetime for low voltage, random wound electrical machines. The analysis is performed on round enameled magnet wire coils, which are aged by accelerated thermal cycles. The obtained results are statistically processed through a two parameter Weibull distribution. According to the findings of the experimental data postprocessing, a lifetime prediction model is built. This model is employed for predicting the lifetime consumption of a motor embedded into an electromechanical actuator for aerospace application.