Problem 4 A single-phase rotating machine has one set of windings on the stator with current Is and one set of windings on the rotor with current Ir. The flux linkages of the stator and the rotor windings are given by: ts = Li + M cos(0)ir tp = M cos(@)is + Lyir In operating this electromechanical system, the currents is and ir are kept constant at I, and Ir, respectively, while the rotor is rotated from 0 = 0 to 0 = 90. Along this path, compute the energy transferred from the mechanical subsystem into the coupling field (i.e. the EFM)