Fault analysis of automotive claw pole alternator rectifier diodes

In today's vehicles with combustion engine claw pole alternators are used as main energy sources. The rectification of the produced alternating voltage is performed by diodes or MOSFETs. Due to the significantly higher costs of MOSFETs, usually diodes are used as rectifiers in vehicles up to the upper class. For self-driving vehicles with a combustion engine the energy distribution system must be redundant and must work in case of a fault. A frequent fault of alternators is a broken or damaged rectifier. The paper provides first an overview about possible faults and fault mechanisms of automotive claw pole alternators. A full fault analysis of 27 claw pole alternators and an extensive investigation of 55,390 alternators and 332,028 rectifier diodes was performed. On this data basis, it could be found that rectifier diodes of an claw pole alternator most often fail in a combination of faults parameter shift and short. The fault open could not be observed in the data.