Rotary electric machine capable of detecting malfunction in switch

A rotary electric machine comprising:

• a stator winding having an output end;
• a rotor including an excitation winding;
• a switch connected to the output end of the stator winding;
• a modulation signal generator configured to:
• generate a modulation signal including information indicative of rotation of the rotor based on change of a voltage at the output end of the stator winding;
• and
• output the modulation signal;
• and
• a rectifying unit configured to alternately turn on and off the switch to rectify the voltage at the output end of the stator winding, thus generating a rectified voltage;
• and
• an excitation current supplying circuit communicably connected to the modulation signal generator via a communication line and configured to start a supply of an excitation current to the excitation winding of the rotor to induce a rotating magnetic field in the stator winding when the modulation signal output from the modulation signal generator is input thereto via the communication line.