Exploring the High-Power Inverter: Reviewing critical design elements for electric vehicle applications

The key components in an electric vehicle (EV) propulsion system are the dc energy source (either a battery or a fuel cell), the inverter, the motor, and the gear reduction. This article will focus on the inverter unit and highlight unique requirements, constraints, and important design considerations. The top-level function of the inverter is to convert dc bus quantities to high-fidelity ac current and voltage required to drive the traction motor. The automotive industry has largely converged on the three-phase current-controlled voltage source inverter as the topology of choice for this application. Other topologies may be considered, though their overriding design constraints are similar and hence will not be discussed here. In particular, the inverter must be powerful, efficient, and reliable and must accomplish these objectives while maintaining low cost, size, and weight. Figure 1 shows a prototype power inverter with every component designed specifically to meet the demanding requirements of today's EV.