Motor drive device

A motor drive device comprising:

• a motor drive unit that generates a current for driving a motor on a basis of a position command and a position detection value of the motor;
• a motor-coil ambient-temperature estimation unit that calculates a motor-coil ambient-temperature estimation value by correcting an output value of a temperature sensor provided in a peripheral portion of a motor coil of the motor by using a filter including both a phase-lead characteristic and a low-pass characteristic;
• a motor-coil increased-temperature estimation unit that calculates a motor-coil increased-temperature estimation value on a basis of the current;
• and
• a motor-coil protection unit that limits the current on a basis of the motor-coil ambient-temperature estimation value and the motor-coil increased-temperature estimation value, wherein
• the motor-coil ambient-temperature estimation unit causes the filter to have the phase-lead characteristic when a temperature increase value calculated on a basis of an output value of the temperature sensor and its immediately previous output value is larger than a predetermined value, and causes the filter not to have the phase-lead characteristic when the temperature increase value is smaller than the predetermined value.