Development and design of spherical induction motors

The first major development described is concerned with the arrangement of stator blocks. A previous paper described a system in which four stator blocks were arranged around the rotor. The new layout involves the use of only two blocks containing pre-skewed slots. The arrangement of the laminations and slotting is such that the two blocks can be rotated as a unit to produce speed adjustment. This arrangement is shown to produce a more uniform effective field velocity over the active surface of the stator. It equalizes the magnetic pull between rotor and stator and has several other design advantages which are fully discussed. The earlier theory of the spherical motor is extended to the case of machines with pre-skewed slots. Test results obtained from several experimental machines are shown. In the light of these results a procedure for designing spherical motors is developed. Several aspects concerning manufacturing procedure, such as the required numbers of rotor bars and rings, have been investigated, and the practical results of these tests are included. A short section of the paper is devoted to the performance of spherical machines when used as induction generators.