Motor drive apparatus and electric power steering apparatus

A motor drive apparatus comprising a control assembly that controls driving of a motor, wherein

• the control assembly includes:
• a controller that outputs a drive signal instructing a drive amount of the motor;
• a drive that supplies electric current, supplied from an external power supply, to the motor based on the drive signal output from the controller;
• a current detector that detects an electric current flowing through the drive;
• and
• a first temperature detector that detects a temperature of the drive;
• wherein
• the control assembly calculates a heat storage amount stored in the control assembly at a predetermined cycle, and when the calculated heat storage amount is larger than a predetermined threshold, the control assembly outputs the drive signal that instructs a drive amount smaller than the drive amount at a time of calculation;
• and
• a heat storage amount Qn calculated at an nth time, where n is an integer equal to or greater than 1, by the controller is a value that is obtained by, when Q0 is a predetermined initial value, adding, to a heat storage amount Qn-1 calculated at an n−1th time, an estimated value of a heat generation amount of the motor obtained based on a voltage of the external power supply, the predetermined cycle, and a current value of the electric current detected, and subtracting an estimated value of a heat release amount obtained based on a difference between the temperature detected by the first temperature detector and a predetermined temperature.