Stator and rotor structures, arrangement of permanent magnets (PMs), and type of coils of PM Vernier machines are reviewed and classified. Then, electromagnetic performance and the energy conversion process in the machine are described. Determination of magnetic field distribution and air-gap permeance of the machine is very complicated than that of other PM machines. Impacts of variations of dimensions in the machine such as the number of modulators on the modulus width and the rotor PMs thickness on the load characteristics (cogging torque, back-EMF, and power factor) are investigated. In addition, principles of flux modulation machines operation are presented and the shape and dimensions of the modulators are optimized. The two-phase and four-phase winding types are used to improve the output power of the machine. Finally, a 150 W PM Vernier generator is designed and prototyped to feed the road speed camera.electric machines and drives, power quality
| INTRODUCTIONDirect-drive systems are widely used in various applications, such as wind generators and electric vehicle (EV) propulsion. 1,2 To regulate speed in low-speed applications, different structures of direct-driven machines have been so far proposed in which the gearbox is removed from the machine, which is considered as the main advantage. [3][4][5] In recent years, many types of direct-driven machines have been introduced, such as transverse flux permanent magnets (PM), flux switching, and flux reversal machines whose performances are based on the properties of flux