Pull-out torque of fractional-slot PM-motors with concentrated winding

Concentrated winding permanent magnet motors, CWPMM and their ability to produce torque are studied. A method for computing the pull-out torque of concentrated winding PM-motors is introduced. A correlation between the pull-out torque and the number of slots per pole and per phase is found. The results obtained indicate how the torque behaves in cases of different types of CWPMMs. Different computation methods to solve the pull-out torque are compared. Finally, a simplified theory to estimate the pull-out torque differences of CWPMMs is presented. For concentrated winding PM-motors that are designed to have the same frame size, the same output power and the same speed, the pull-out torque is proportional to the number of stator slots per pole and per phase. This correlation may help the motor designer to select the suitable number of poles and slots in accordance with the desired pull-out torque.