Design of a variable-flux permanent magnet synchronous motor for adjustable speed operation

This paper suggests design of variable flux motor for variable speed operation. The calculation method of electrical parameters to meet variable speed condition is suggested, and the basic motor shape is decided using the relationships between the calculated electrical parameters and motor geometry. The difference between corecivity of two types of magnet is used to control flux. To prevent irreversible demagnetization of low corecivity magnet, the approximate shape of magnet is decided by calculating the operating point of magnet using an equivalent magnetic circuit. The optimum design of magnet shape considering the non-linear characteristics is suggested using finite element method. To verify the validity of the design, magnetizing/demagnetizing and load operation tests are conducted.