Multiphase brushless AC electric machine

DETAILED DESCRIPTION According to the present invention, there is provided a multiphase brushless AC electric machine comprising: a stator frame having a surface provided with parallel slots and projections disposed alternately, each of said slots having an opening onto said surface, each of said openings being substantially as wide as the widest width of the corresponding slot; and a rotor frame having a surface provided with permanent magnet means having respective surface sections facing said slots and projections, each of said surface sections facing a number of said slots which corresponds to a number of phases upon which said machine operates, all of said surface sections of said magnet means producing a magnetic flux density having a component average amplitude B, (.
theta.
) perpendicular to the corresponding surface of the stator, which is substantially defined by the following equation: B.
sub.
r (.
theta.
)=M.
sub.
r (.
theta.
).
multidot.
L.
sub.
a (.
theta.
)/L.
sub.
v (.
theta.
) where L.
sub.
a (.
theta.
) is defined by the following equation: ##EQU2## where .
theta.
is a position angle in radians with respect to a reference position on said rotor frame; B.
sub.
r (.
theta.
) is said component average amplitude at said position angle .
theta.
; L.
sub.
v (.
theta.
) is a gap distance between said projections and said surface of said rotor frame at said position angle .
theta.
; M.
sub.
r (.
theta.
) is a component of residual induction of said magnet means at said position angle .
theta.
, M.
sub.
4 (.
nu.
) being perpendicular to the corresponding surface of the stator, M.
sub.
r (.
theta.
) being alternative with a period corresponding to 4.
pi.
/K; K is an even number representative of all of said surface sections; and C is an arbitrary constant, whereby, in operation, said rotor frame is magnetically coupled to said stator frame while reducing losses due to harmonic distortion of magnetic flux density within said stator frame, having a torque versus current curve that is linear within a larger current band and reducing cogging torque between said stator frame and said rotor frame