Machine Design and Precision Current Regulation for the Parallel DPNV Bearingless Motor Winding

Abstract

The parallel dual-purpose no-voltage (DPNV) winding topology offers appreciable advantages for high speed and significant power bearingless motor designs. Precision current regulation is required to realize the high-performance potential of bearingless motors using parallel DPNV windings. The performance of the machine hinges on the ability to decouple the voltage disturbance between the torque and suspension systems at all operating conditions, including high electrical frequencies. Two pathways are investigated to achieve precision actuation: 1) machine design and/or feedforward control to systematically reduce the voltage disturbance, and 2) direct digital design of the current regulator for high-speed operation. Analytical models are constructed, which gives insight into the root cause of the cross-coupling as a function of the physical winding design. It is shown that all practical machine designs produce some level of voltage disturbance which can be directly eliminated via a feedforward voltage added to the torque winding current regulator. The state-of-the-art current regulation methods for the parallel DPNV winding are progressed to enable extended operating ranges for the targeted high speed and bandwidth conditions. By codesigning the machine and controls, more optimized designs are possible by trading off torque ripple and force density.