Starter-alternator for hybrid electric vehicle: comparison of induction and variable reluctance machines and drives

This paper presents the experimental results of using induction and variable reluctance machines as the starter-alternator in a hybrid electric vehicle. The frame sizes of these machines are dictated by transient engine cranking loads. Therefore, in their design, the machines are assumed to be in deep magnetic saturation and the resultant thermally constrained electric loadings are predicted from the calculated electromagnetic air gap surface traction. This design approach results in machine performance predictions in close agreement with prototype measured results for the induction machine. Similar conditions hold for the variable reluctance machine. Experimental results show that both machines require substantial inverter kVA rating to meet magnetizing and overdrive requirements. The series configured induction motor developed 300 Nm of torque at 250 RPM with 115 A/sub RMS/ phase current from the inverter drive whereas in its parallel connection it required nearly 240 A/sub RMS/. The same held for the variable reluctance machine.