IEC TS 61857-42:2025

Electrical insulation systems - Procedures for thermal evaluation - Part 42: Specific requirements for evaluation of an electrical insulation system (EIS) used for road transportation applications

IEC TS 61857-42:2025 provides a procedure to evaluate the lifetime of an electrical insulation system (EIS) in a drivetrain unit within road transportation (automotive) applications. Typical applications include motors and generators in hybrid and full electric passenger vehicles, light-duty and heavy-duty commercial vehicles, as well as buses.
In general, the IEC 61857 series is applicable to EIS used in electrotechnical products with an input voltage of up to 1 000 V where the predominant ageing factor is thermal. In the context of this document the limit of 1 000 V is understood to be the application-specific battery DC voltage.
The EIS evaluated by this procedure will operate free from partial discharges over its whole lifetime.
Evaluation of EIS in the following applications is outside the scope:
- motors and generators within the scope of IEC TC 2, Rotating machinery;
- rail traction machines in the scope of IEC TC 9, Electrical equipment and systems for railways;
- motors and generators for road vehicles that are not intended for the traction of them.

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