Patent ID: 7358638

Claim:
A method of determining a pole arc ratio of an interior permanent magnet rotary motor, said interior permanent magnet rotary motor comprising: a stator including a stator core having N slots and N magnetic pole sections (N: a natural number of 2 or more) arranged to be spaced at equal intervals in a peripheral direction thereof and exciting windings of at least two phases wound on said N magnetic pole sections; and a rotor having a rotor core and P permanent magnet magnetic pole sections (P: an even number), said rotor rotating with respect to said stator; said P permanent magnet magnetic pole sections being formed within said rotor core to be spaced at equal intervals in a peripheral direction of said rotor core; each of said P permanent magnet magnetic pole sections being constituted from a permanent magnet embedded within said rotor core; and a ratio of the P to the N being set to be larger than 43/45; wherein said pole arc ratio of said permanent magnet magnetic pole section indicated by Ψ p is determined by calculation using the following expression: Ψ p =2 mP/N+P/ 4 LCM ( P, N )−2 n+kP/LGM ( P, N ) wherein LCM(P, N) is a least common multiple between the P and the N, m and n are arbitrary natural numbers, k is an arbitrary integer, and the Ψ p is a value larger than zero but smaller than one.