Operating Principle and Characterisation of a Novel Contra-Rotating Dual-Rotor Switched Reluctance Machine

This paper proposes a novel dual mechanical port machine composed of a stator with a single set of concentrated windings with two coaxially housed rotors. The machine has the unique property that the rotors are capable of rotating in opposite directions while being controlled by the same stator windings. Mechanical gears, two separate machines or dual-rotor machines with multiple sets of stator windings are usually employed to produce contra-rotation. By housing two rotors into a single stator the system complexity and component count is reduced as only a single converter is necessary. For balanced loads, the machine has lower copper losses and higher power density compared to using two separate machines. The operating principle is explained and an equivalent magnetic and electrical model of the machine is developed. The torque characteristic as a function of the phase switch-on angle is derived for each rotor from which the possible operating modes of the machine and their applications are established. The superposition of the rotor fluxes is validated and discussed for each operating mode. Additionally, the experimental results demonstrate the stability of the machine as a double motor at no-load as well as at unbalanced load conditions.