Assume that the VRM of Examples 8.1 and 8.3 is modified by replacing its rotor with a rotor with 75° pole-face angles as shown in Figure a. All other dimensions and parameters of the VRM are unchanged.

a. Calculate and plot L (θm) for this machine.

b. Repeat Example 8.3 except that the constant voltage 100 V is first applied at θm = - 67.5° when dL (θm)/d θm becomes positive and the constant voltage of- 100 V is then applied at 0m = -7.5 ° (i.e., when dL (θm)/d θm becomes zero) and is maintained until the winding current reaches zero.

c. Plot the corresponding torque.