Rotation angle detection apparatus

A rotation angle detection apparatus that includes:

• a magnet that is provided to a rotating shaft of a rotating body and rotates with the rotating shaft to generate magnetic flux;
• and a magnetic sensor that is provided to face the magnet and detects a magnetic flux interlinked with the magnetic sensor, the apparatus comprising:
• a magnet magnetic flux detection circuit that detects a magnet magnetic flux generated from the magnet;
• a disturbance magnetic flux detection circuit that has a relationship between a disturbance magnetic flux and a field current flowing through a field winding of the rotating body, the disturbance magnetic flux being a magnetic flux other than the magnet magnetic flux and being interlinked with the magnetic sensor, the disturbance magnetic flux detection circuit being configured to:
• measure a value of the field current;
• and
• detect, based on the relationship, a value of the magnetic flux that corresponds to the measured value of the field current;
• and
• a correction circuit that corrects a result of detection of the magnetic sensor based on a result of detection of the magnet magnetic flux detection circuit and a result of detection of the disturbance magnetic flux detection circuit.