Permanent magnet arrangement to increase torque density of motor

What is it about?

This study proposes an improved rotor structure that can increase the torque density of a permanent magnet synchronous motor. The air-gap flux density of the improved rotor-type motor is calculated using an equivalent magnetic circuit (EMC) and compared with the calculation result that is obtained using finite element analysis (2D-FEA). In addition, the no-load fundamental air-gap flux density of the surface-mounted permanent magnet motor (SPM), interior permanent magnet motor (IPM), spoke-type motor, and improved rotor-type motor are compared using 2D-FEA. Changes in the no-load fundamental air-gap flux density according to changes in the rotor diameter and PM usage are examined for each rotor type. A comparison of the fundamental air-gap flux densities of the five rotor types, including the improved rotor-type conducted using 2D-FEA demonstrated that the air-gap flux density of the improved rotor-type was highest.

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Why is it important?

One way to reduce the material cost of PM motor is to reduce the size of the electrical machine. However, maintaining the same performance while reducing the size of the electrical machine requires using more permanent magnets (PM), which leads to increased cost. This study proposes an improved rotor structure to increase the flux per pole without increasing the PM usage of the PM motor.