Improving the torque output in radial- and axial-flux permanent-magnet synchronous machines with concentrated windings by using a combined wye-delta connection

In this paper, a combined wye-delta connection is introduced and compared with a common wye-connection of a concentrated winding. Because the combined wye-delta connection has a higher fundamental winding factor, the output torque is higher for the same current density when a sinusoidal current is imposed. As the combined wye-delta connection has only a minor influence on the losses in the machine, the efficiency of the machine is also increased. The combined wye-delta connection is illustrated in detail for an axial-flux permanent-magnet synchronous machine with a rated power of 4.5 kW at a fixed speed of 2500 rpm, using finite element computation.