Design concepts for a 3-phase axial peg style electrostatic rotating machine utilizing variable elastance

Rotating electric machinery is usually constructed of iron/steel laminations, copper windings, and permanent magnets. This paper investigates fluid-filled, electrostatic rotating machines for the ultimate ambition of transitioning fundamental magnetic materials to dielectrics in order to reduce production costs. The study of the axial-peg-style electrostatic rotating machine focuses on basic geometric and material knowledge and the creation of design tools. An axial peg machine possesses interdigitated pegs (cylinders) that come into, and out of, radial alignment as the machine rotates causing variable capacitance between the stator and rotor. A prototype with peak torque of 0.7N-m and gap field strength of 15kV/mm was constructed. The specific torque density of the machine is 0.101N-m/kg, comparable to fractional horsepower NEMA class induction machines. This was achieved by filling the machine with a dielectric fluid, whose relative permittivity is 7.1, rather than the ultra-high vacuum typically employed in canonical electrostatics. Experimental measurements presented include angular capacitance, peak torque and torque-per-volt under stall conditions. Construction techniques are discussed in detail.