Patent ID: 9647601
Date: 2017-05-09
CPC Classifications: H02P

Claim:
1. A motor control device comprising: a driving circuit that carries out PWM (Pulse Width Modulation) control of voltage to be applied to a motor in accordance with a duty ratio command value; a voltage detector that detects applied voltage to the motor; a coil temperature estimator that estimates a coil temperature of the motor from coil equivalent resistance, heat capacity and thermal resistance of a coil of the motor, which are given in advance, from the applied voltage the voltage detector detects, and from the duty ratio command value; a temperature abnormality decider that decides whether the coil temperature the coil temperature estimator estimates is a normal temperature or not; and a duty limiter that limits the duty ratio command value at a low value when the temperature abnormality decider decides that the coil temperature is not the normal temperature, wherein the coil temperature estimator calculates power consumption W of the motor per unit time according to the following Expression, and estimates the coil temperature by calculating and integrating a coil temperature rise per unit time corresponding to the power consumption W using the heat capacity and the thermal resistance,  where V is the applied voltage the voltage detector detects, R is coil equivalent resistance given to the coil temperature estimator in advance, and f(x) is a function whose variable x is the duty ratio command value.