High-speed reluctance machines with mixed-pole windings

The mixed-pole winding produces two high-pole-number rotating fields rotating at their respective synchronous speeds. If the difference between the two component field pole numbers is chosen to be two, then the modulation wave has one pole and rotates at a speed of 6000 RPM for 50 Hz supply frequency. A reluctance-type rotor may be constructed to rotate with the modulation wave and so to produce a machine rotating at the synchronous speed corresponding to a one-pole machine. The authors describe the development of a series of experimental rotors which demonstrate this behaviour for frequencies up to 12.5 Hz with corresponding speeds up to 1500 RPM. A particular challenge is to generate worth-while torque from the interaction with the modulation wave while suppressing high-frequency torque ripple caused by interaction with the separate high-pole-number component waves. Problems of mechanical balance and unbalanced magnetic pull are discussed