Patent ID: 7126309

Claim:
An electric machine comprising: a first coil group containing a plurality of coils arranged along a specified direction; and a magnet group facing the first coil group and capable of moving relative to the first coil group along the specified direction; wherein the first coil group is classified into M phase sub coil groups each constituted by n coils where M is an integer of 2 or more and n is an integer of 1 or more, and the coils of the sub coil groups are aligned in sequence one at a time with a specified sub coil group interval Dc from the first phase sub coil group to the M-th phase sub coil group along the specified direction, the sub coil group interval Dc is set to a value of K/M times a magnetic pole pitch Pm (K is a positive integer excluding an integral multiple of M) where the magnetic pole pitch Pm is defined, in relation to the magnet group, to be a distance corresponding to an electrical angle of n along the specified direction, the adjacent sub coil groups are driven at a phase difference of (K/M)π, and each coil has substantially no magnetic material core.