High Torque Density Macro-scale Electrostatic Rotating Machines: Electrical Design, Generalized $d-q$ Framework, and Demonstration

The use of advanced dielectric liquids and manufacturing techniques for enhanced surface area per unit volume, along with other multiplicative gains, is enabling macro-scale electrostatic machines with competitive torque densities. This emergence prompts the need for circuit modeling-that guides machine design and drive controls-rooted in the canon of well-established electromagnetic machinery practices. In this study, prior dielectric and manufacturing innovations are combined with a newly developed unified electrostatic machine d-q-axis framework to form a machine that demonstrates industrial utility. Design, equivalent circuits, and performance are validated by an experimental prototype intended for low-speed direct-drive servo actuators. A prototype electrostatic machine was constructed entirely of aluminum and printed circuit boards, and possesses active material torque densities ≥1.4 N·m/kg and ≥2.65 N·m/L without the need for forced air or liquid cooling. Additional features include near zero loss at stall and low torque ripple.