| 摘要 |
The present invention relates to a field element which reduces a harmonic component of a magnetic flux density. Permanent magnets (20) are in contact with first magnetic plates (1, 3) in a direction parallel to a rotation axis (P). The first magnetic plate (1) includes first and second magnetic members (10, 12) and first and second non-magnetic members (11, 13). The first magnetic member (10) includes a pole center and is in contact with one of the permanent magnets. The first magnetic member (10), the first non-magnetic member (11), the second magnetic member (12) and the second non-magnetic member (13) are disposed in the stated order in a circumferential direction with the pole center and the rotation axis being as a starting point and a center, respectively. When Pn represents the number of pole pairs and i represents an odd number equal to or more than three, an angle &thetas;1 defined by an end portion (131) of the second non-magnetic member (13) on the pole center side with respect to a pole gap is 0<&thetas;1<180/(i·Pn). An angle &thetas;2 defined by an end portion (111) of the first non-magnetic member (11) on the pole center side with respect to the pole gap is 180/(i·Pn)≦̸&thetas;2≦̸180·2/(i·Pn).
|
