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Increasing demand of Electric and Hybrid vehicles questions more about Reliability and Lifetime of electronic circuits associated with them. It is very important for a hardware circuit designer to evaluate if module will last the expected lifetime. This paper elaborates the methods and steps to find the expected lifetime of critical components; and to decide whether Hybrid Power Electronics Unit (PEU) will meet the OEM requirements on lifetime. Accelerated thermal stress method is used to determine the required High Temperature Operational Life (HTOL) hours for given thermal profile of Hybrid vehicle passenger car in driving (8,000Hrs), charging(30,000Hrs) and total lifetime (38000Hrs ≈ 15Years). Example calculation of required HTOL hours against expected lifetime for critical component from Hybrid ECUs is explained in this paper. Also inclusions and exclusions of this method in evaluating lifetime assessment are also discussed here.

Incorporation of Personal safety design concepts in Hybrid Electric Vehicle (HEV) and Electric Vehicle (EV) application gains precedence due to the use of High Voltage Components and rechargeable energy storage systems (RESS) like Battery, DC-Link Capacitor(Bulk Capacitor to handle the motor current ripples). The Voltage levels above 60V DC/ 30 V AC rms are dangerous to human lives. Sufficient isolation resistance keeps the body currents within safe limits. International standards like SAE J2344, ISO 6469, and IEC 60664 provide guidelines to ensure personal safety in vehicles which use high voltage components. This paper proposes electric circuit concepts which are recommended to implement in a PEU to ensure personal safety. The recommendations from the standard ISO6469 with respect to high voltage wiring and marking of high voltage components are discussed in the paper.