A method of estimating an operating state of a drive system is presented. The drive system comprises an electric motor and a mechanical unit being moved by the electric motor. The method comprises a) operating the electric motor using electrical properties, b) determining movement properties regarding the movement of the mechanical unit using the electrical properties, repeating steps a) and b) for a number of times using changed electrical properties, and generating a distribution function. The distribution function allocates electrical properties to the resulting movement properties. The method also comprises estimating the operating state in response to the generated distribution function.

A method of estimating an operating state of a drive system is presented. The drive system comprises an electric motor and a mechanical unit being moved by the electric motor. The method comprises a) operating the electric motor using electrical properties, b) determining movement properties regarding the movement of the mechanical unit using the electrical properties, repeating steps a) and b) for a number of times using changed electrical properties, and generating a distribution function. The distribution function allocates electrical properties to the resulting movement properties. The method also comprises estimating the operating state in response to the generated distribution function.

A motor controller includes: a rotation speed estimating unit that estimates a rotation speed of an motor on the basis of current information and primary frequency information of the motor; a proximity switch that outputs an ON signal when a portion of a rotating body of the motor is in proximity and outputs an OFF signal when a portion of the rotating body of the motor is not in proximity; a rotation speed computing unit that computes a rotation speed of the motor on the basis of the ON signal and the OFF signal output from the proximity switch; and an abnormality detection unit that detects an abnormality in the rotation speed estimation value or an abnormality in the proximity switch when a difference between the estimated rotation speed estimation value and the computed rotation speed computation value is equal to or larger than a threshold.

A motor drive apparatus includes: a converter which converts AC power to DC power and to output the DC power to a DC link; an inverter including power devices which converts the DC power to AC power for driving a motor; a capacitor provided in the DC link; a shut-off circuit to open and close an electrical path between the AC power source and the converter; a constant current control unit which performs control in such a manner as to allow a constant current supplied by the capacitor to pass through a detection target power device among the power devices in the inverter; and an abnormality detection unit which detects an abnormality in the detection target power device based on changes in voltage between a collector and an emitter of the detection target power device during a period in which the constant current passes through the detection target power device.

A motor controller includes: a rotation speed estimating unit that estimates a rotation speed of an motor on the basis of current information and primary frequency information of the motor; a proximity switch that outputs an ON signal when a portion of a rotating body of the motor is in proximity and outputs an OFF signal when a portion of the rotating body of the motor is not in proximity; a rotation speed computing unit that computes a rotation speed of the motor on the basis of the ON signal and the OFF signal output from the proximity switch; and an abnormality detection unit that detects an abnormality in the rotation speed estimation value or an abnormality in the proximity switch when a difference between the estimated rotation speed estimation value and the computed rotation speed computation value is equal to or larger than a threshold.

A motor drive apparatus includes: a converter which converts AC power to DC power and to output the DC power to a DC link; an inverter including power devices which converts the DC power to AC power for driving a motor; a capacitor provided in the DC link; a shut-off circuit to open and close an electrical path between the AC power source and the converter; a constant current control unit which performs control in such a manner as to allow a constant current supplied by the capacitor to pass through a detection target power device among the power devices in the inverter; and an abnormality detection unit which detects an abnormality in the detection target power device based on changes in voltage between a collector and an emitter of the detection target power device during a period in which the constant current passes through the detection target power device.