Sensorless Control of Separately Excited Synchronous Electrostatic Machines

This article presents the analysis and demonstration of sensorless position estimation methodologies for separately excited synchronous electrostatic machines (SEMs). The torque density of the SEM comes at the cost of a high pole count (p >50) along with other enhancements. The high pole count makes the use of high-resolution position sensors necessary, driving up the cost of the system. The sensorless estimation of rotor position is seen as a solution for alleviating the need for high-resolution and high-cost position sensors. Key features of electrostatic machines that make them suitable for sensorless operation are identified. Back MMF (current) based rotor position sensing for medium to high speeds is investigated. High-frequency injection-based position estimation is investigated for zero and low-speed operating regions. The proposed methods are experimentally demonstrated using a current-source inverter-based drive platform.