Comparative Study of DC-Link Capacitor Size for Two and Three Phase Permanent Magnet Synchronous Machines

Two-phase open winding electrical machines have been proposed in the literature for their benefits in terms of peak torque and low noise emission. For this type of open-winding motors, a 4-leg power converter is required, allowing a power increase of 15% at the cost of one additional converter leg. This paper focuses on the impact of the two-phase open winding solution on the size of the DC-link capacitors, which is not covered in the literature. With reference to a state-of-the-art concentrated-winding 12slot/10pole 3ph PMSM drive, the DC-link RMS current stress and voltage ripple are comparatively analysed for different operating conditions. The simulations show that, under the same mechanical power conditions, the DC-link capacitor in the two-phase machine experiences lower voltage stress and similar RMS current compared to its three-phase counterpart. This effect impacts the cost, volume, and weight of the DC-link capacitor, partially compensating for the additional inverter leg required by the two-phase solution.