MS student Michael Stoens with Advisor K. Haran

With the rapid adoption of electrification, power density, reliability, and fault tolerance of electric drive systems are becoming increasingly important. The U.S. Department of Energy has established future targets for power density in power electronics, electric motors, and electric tractive drive systems. To meet these targets, research is focusing on higher power, lighter weight systems.

One promising approach to improving motor power density is the use of slotless permanent magnet synchronous machines (PMSMs). This architecture reduces the iron content in the machine by eliminating stator teeth. However, removing the stator teeth significantly lowers the per-phase inductance. Traditional voltage source inverters (VSIs) rely on motor inductance to filter output current, making them less suitable for low-inductance machines.

A potential alternative is the Current Source Inverter (CSI). CSIs utilize a DC link inductor to maintain constant input current, which is then sinusoidally commutated to the load. This eliminates the inverter’s dependence on motor inductance for current filtering, making CSIs a strong candidate for driving slotless PMSMs.

This work investigates the implementation of a CSI using modern semiconductor devices and advanced control techniques for driving slotless PMSMs. The goal is to evaluate its feasibility, performance, and potential advantages over conventional drive systems in high-power-density applications.

Figure 1. Whole Current Source Inverter (CSI).