A switched elastance electrostatic machine constructed from sustainable elements for rotational actuators

A rotating electric machine built entirely of sustainable lightweight materials is presented for rotary actuator applications. The machine uses electrostatic forces instead of magnetic, enabling different materials. Here, aluminum, plastic, and printed circuit boards are used as they are low cost and easily recycled at end of life. The electrostatic machine developed is of the axial flux variety, utilizing the switched elastance mode of operation, i.e. a dual of a switched reluctance machine. Cascaded disks whose conducting vanes/poles (surfaces) align and misalign during rotation are immersed in a dielectric liquid of sufficient energy density to enable higher torque output. The liquid drag torque limits efficiency at higher speeds as a motor, but is ideal for low speed rotary actuation. A prototype electrostatic machine was built in a NEMA 42 frame form factor for general comparison. While operating at 9 kV, the machine provides 1.9 N-m average torque constituting torque densities of 0.5 N-m/kg (specific) and 1.2 N-m/L (volumetric). The machine's low conduction loss and large internal surface area eliminates virtually all cooling needs and stall torque can be held indefinitely.