Forces on the Teeth in D-C Machines

The tangential forces of magnetic origin causing useful torque of a d-c armature (further called only forces) are the resultants of (1) forces on slot sides due to magnetic fields along them and (2) forces on slot conductors due to interaction between magnetic fields and conductor currents. Force on tooth is the sum of forces on its sides and forces on conductors of one adjacent slot. The distribution of forces on singular teeth under a pole does not follow the distribution of magnetic flux on these teeth, but generally, the variation in tooth forces is greater.