Shift range switching system

A shift range switching system, comprising:

• a motor that includes a plurality of motor windings and generates a cogging torque by a permanent magnet;
• a plurality of drive circuits that switch energization of the motor windings;
• an output shaft to which rotation of a motor shaft as a rotation shaft of the motor is transmitted;
• a shift range switching mechanism that includes a trough providing member having a plurality of troughs and a plurality of crests separating the troughs from each other, and integrally rotates with the output shaft, an engagement member that fits in one of the troughs corresponding to a shift range, and an urging member that urges the engagement member in a direction of fitting into one of the troughs;
• and
• a control unit that includes at least one calculation unit for performing a calculation related to a drive control of the motor, wherein:
• an allowance is provided between the motor shaft and the output shaft;
• the engagement member drops into the one of the troughs with the allowance;
• the drive circuits, the motor windings, and a plurality connection wirings connecting the drive circuits and the motor windings are defined as a plurality of motor drive control systems;
• the cogging torque transmitted to the output shaft is defined as an output shaft cogging torque;
• an intermediate range stop abnormality is defined that the output shaft stops when balancing the output shaft cogging torque and a torque including a load torque of the urging member;
• and
• when an abnormality occurs in the motor drive systems in an ascending action in which the engagement member moves from one of the troughs toward an adjacent one of the crests, the shift range switching systems avoids an occurrence of the intermediate range stop abnormality.