Improved rotor structures for increasing flux per pole of permanent magnet synchronous motor

This study proposes an improved rotor structure that can increase the flux per pole of apermanent magnet synchronous motor. The air‐gap flux density of the improvedrotor‐type motor is calculated using an equivalent magnetic circuit and comparedwith the calculation result that is obtained using finite element analysis(FEA). In addition, the no‐load fundamental air‐gap flux density of thesurface‐mounted permanent magnet motor, interior permanent magnet motor,spoke‐type motor, and improved rotor‐type motor are compared using FEA. Changesin the no‐load fundamental air‐gap flux density according to changes in therotor diameter and permanent magnet usage are examined for each rotor type. Acomparison of the fundamental air‐gap flux densities of the five rotor types,including the improved rotor‐type conducted using FEA demonstrated that theair‐gap flux density of the improved rotor‐type was highest. A comparison of theno‐load phase back EMF of the five types was conducted after designing them inthe four‐pole six‐slot structure. Each rotor type is applied to 80 W‐grade fanmotors, and the torque ripple and iron loss are compared. A prototype of theimproved rotor‐type motor is developed, and the no‐load phase back EMF and loadtest result are verified through experiments.