Synchronous protruding pole motors do not have a squirrel cage in the rotor and the polar shoes during the start behave as if they were a cage. The effect of eddy current caused by the rotating field Gates B94 Hi-Power II Belts on the surface of the pole shoes during starting will produce high currents in those regions. Such currents produce high electromagnetic fields that interact with the rotating field produced by the stator, resulting in the starting torque of the machine.
The configuration of the polar shoes of this type of motor can be combined during its design, in order to adjust the starting current and starting torque of the machine, optimizing it the load to be driven, the method and the starting conditions requested by the application. Due to the effects that are manifested in the polar shoes during the start and the very principle of obtaining the starting torque, high levels of torque are obtained at the start with small current levels.
The circulation of high eddy currents in the pole shoes causes high temperatures in this region, which in the design of the machine must also be considered, with respect to the material of the shoes themselves, insulation materials and fixing of the field windings and also the way of cooling the poles.