Breakdown resistance analysis of traction motor winding insulation under thermal ageing

Abstract

Stator inter-turn faults are among the most important electric motor failures as they progress fast and lead to catastrophic motor breakdowns. Inter-turn faults are caused due to the windings' insulation degradation. The main stress which deteriorates the insulation is the thermal one. Proper understanding of how this stress influences the electrical properties of insulation over time may lead to reliable prognosis and estimation of the motor's remaining useful life. In transport applications where reliability and safety come first it is a critical issue. In this paper, extensive experimental testing and statistical analysis of thin film insulation for traction motor windings has been performed under fixed thermal stress. The results indicate that for high thermal stress the electrical properties of the insulation material present a non-monotonic behavior thus proving the well-known and established Arrhenius law inadequate for modelling this type of problems and estimating the remaining useful life of thin film insulation materials.

The Insulation Resilience of Inverter-Fed Low Voltage Traction Machines: Review, Challenges, and Opportunities

“…As a result, this aspect is not further discussed here. In summary, it can be stated that, despite a large number of publications, there is more dissent than consent about the influencing factors and their impact on measurable aging [43], [77], [119]- [121] tan(δ) ↑ [117], [121] IR ↓ [89], [119]- [122] electrical voltage type PDIV [2], [60], [68], [108], [112], [113], [123]-[125] ↔ [43], [76] polarity [35], [76], [108], [109] ↔…”

Influence of Insulation Thermal Aging on the Temperature Assessment in Electrical Machines

“…Thermal aging is surely considered as one of the main stressing factors affecting the lifetime and reliability of EMs' insulation systems [15,[33][34][35]. When an insulating material is subject to a high temperature, a number of Arrhenius-type reactions are triggered within the material's chemical bonds [36].…”

Influence of Thermal Aging on the Winding Thermal Conductivity in Low Voltage Electrical Machines

“…In conventional EMs, the winding is generally the hottest spot, as most of the losses are concentrated within its volume [14]. On top of that, the thermal aging of the winding insulation system (mainly the interturn insulation) is one of the major initiators of stator failures [15,16]. Accordingly, a proper thermal management of the winding is essential for guaranteeing a satisfactory lifespan, characterized by low failure probability [17].…”