Patent ID: 7791296

Claim:
A motor protection system provided with a motor, a motor driver that controls current supplied to the motor, a temperature estimating unit that estimates the temperature of the motor based upon the current supplied to the motor and an overheating prevention unit that limits an upper limit value of the current supplied to the motor according to the estimated temperature of the motor, comprising: a current value correcting unit for correcting the limited upper limit value of the current supplied to the motor to be a larger value, wherein when the current upper limit value is limited by the overheating prevention unit, the temperature estimating unit estimates the temperature of the motor using the corrected upper limit value of the current supplied to the motor, wherein the overheating prevention unit limits the upper limit value of the current supplied to the motor at a current limiting ratio according to the temperature of the motor when the temperature estimated by the temperature estimating unit of the motor rises to a predetermined value and the current value correcting unit corrects the upper limit value to be a larger value according to the current limiting ratio, and wherein a current limiting ratio resetting unit resets the current limiting ratio to be 1.0 when the current limiting ratio is reduced to a preset value in the vicinity of zero.