Motor control device including torque command limit unit

A motor control device which controls a motor in a machine tool or an industrial machine, the motor control device comprising:

• a power failure detection unit that detects a power failure of a power source which supplies electric power for driving the motor;
• a DC link voltage detection unit that detects a value of a DC link voltage applied to an amplifier which drives the motor;
• a switch unit which switches a connection destination of the motor to the amplifier or a dynamic brake resistance;
• a voltage comparison unit which compares the value of the DC link voltage with a predetermined threshold value;
• a torque limit value setting unit which sets a torque limit value for decelerating the motor in accordance with a result of comparison by the voltage comparison unit;
• a torque command limit unit which limits a torque command for driving the motor to the torque limit value when the motor is connected to the amplifier when the power failure is detected;
• a velocity detection unit which detects an angular velocity of the motor;
• a torque prediction value calculation unit which calculates, using the angular velocity detected by the velocity detection unit, a deceleration torque of the motor that is predicted to be generated when the motor rotating at the angular velocity is connected to the dynamic brake resistance as a torque prediction value;
• and
• a torque comparison unit which compares the torque limit value set by the torque limit value setting unit with the torque prediction value calculated by the torque prediction value calculation unit, wherein in accordance with a result of comparison by the torque comparison unit, the switch unit switches the connection destination of the motor when the power failure is detected to the amplifier or the dynamic brake resistance.