Patent ID: 7405505

Claim:
A rotary electric machine comprising: a frame; a stator whose stator-slot number Ns is 12; a rotor whose rotor-pole number Np is 8, the rotor and being disposed inside the stator wherein, the frame has a frame thickness T(θ) at mechanical angle θ, with respect to a reference line that connects an inner circumferential center of the frame with an arbitrary point, other than the center, and the frame thickness around the center is circularly expanded in a Fourier series as expressed by equation (1), T ⁡ ( θ ) = ∑ n = 0 ∞ ⁢ T n ⁢ cos ⁡ ( n ⁢ ⁢ θ + ϕ n ) ( 1 ) (where n is 0, 1, 2, 3, . . ., T n is the magnitude of the n-th component of the frame thickness when T(θ) is expanded in the Fourier series as in equation (1), and φ n is phase), the difference between the stator-slot number Ns and the rotor-pole number Np is k (k=|Ns−Np|), and stress-relieving spaces are located in portions of the frame in an arrangement that does not have 90-degree mechanical angle rotational symmetry, in such a way that the sum P of inclusion ratios for the k-th component T k and the Np-th component T Np , which are the Fourier series expansion coefficients for the frame thickness T(θ) expressed by equation (2) P = ( T k + T N ⁢ ⁢ p ) / ∑ n = 0 ∞ ⁢ T n × 100 ⁡ [ % ] , ( 2 ) is less than 12%.