TH99103B - Electrical motor diagnostic equipment and switching devices. - Google Patents

Abstract

For each electric motor, a zero-phase sequence current detection unit, a phase current detection unit, and a phase voltage detection unit are installed. Four different types of motor faults are detected solely through voltage-current analysis. The voltage-current analysis procedures for detecting these four different types of motor faults are then defined in a predetermined sequence. Furthermore, the monitoring interval is adjusted by a monitoring interval adjustment unit within the monitoring and diagnostic unit based on the level of motor fault determination, the length of the motor's operating history, or the motor's importance level.

Claims (13)

Revised June 30, 2017 1. The electric motor diagnostic unit (50) is equipped with a phase current detector (5) for detecting the phase current of the power source circuit connected to one or more electric motors (7), a zero-phase sequence current detector (4) for detecting the zero-phase sequence current of the power source circuit, and a monitoring and diagnostic unit (8, 48) for determining faults in the electric motor based on the outputs of the phase current detector and the zero-phase sequence current detector. The electric motor diagnostic unit is arranged so that, based on the analysis of the power source circuit's phase current and its zero-phase sequence current in the monitoring and diagnostic unit, the detection of motor faults includes four different types of fault detection: line-to-ground fault detection, which is the detection of a state in which the electrical circuit is electrically connected to ground with relatively low impedance; inter-layer short circuit detection, which is the detection of short circuits between the winding layers of the electric motor; bearing fault detection, which is the detection of faults in the bearings of the electric motor shaft; and torque fault detection, which is the detection of faults in the torque of the electric motor shaft. Furthermore, the initial design relies on fault detection between the line and ground. The electric motor diagnostic device comprises a phase current detection unit for detecting the phase current of the power source circuit connected to one or more electric motors; a phase voltage detection unit for detecting the phase voltage of the power source circuit; a zero-phase sequence current detection unit for detecting the zero-phase sequence current of the power source circuit; and a monitoring and diagnostic unit for determining faults in the electric motor based on the outputs of the phase current, phase voltage, and zero-phase sequence current detection units. The electric motor diagnostic device is arranged so that, based on the voltage-current analysis of the electric motor in the monitoring and diagnostic unit, it undergoes fault detection. This includes four different types of fault detection: line-ground fault detection (detection of a state where the electrical circuit is electrically connected to ground with relatively low impedance), inter-layer short circuit detection (detection of short circuits between the layers of the electric motor windings), bearing fault detection (detection of faults in the bearings of the electric motor shaft), and torque fault detection. Detecting anomalies in the rotational moment of the motor's shaft, and initially also detecting faults between the wire and ground. 2. The electric motor diagnostic equipment as specified in Claim 1, whereby the monitoring and diagnostic unit shall include at least one display unit for displaying the electric motor malfunction when its malfunction is detected, and a warning unit for notifying the electric motor malfunction when its malfunction is detected. 3. The electric motor diagnostic equipment as specified in Claim 1 or Claim 2, where, in the event that an electric motor fault is detected by the monitoring and diagnostic unit, the four types of fault detection procedures shall be in the sequence of line-to-ground fault detection, interlayer short circuit detection, bearing defect detection, and torque fault detection, or in the sequence of line-to-ground fault detection, bearing defect detection, interlayer short circuit detection, and torque fault detection. 4. One of the following electric motor diagnostic devices as specified in Claims 1 through 3, whereby an adjustment monitoring unit shall be provided in the monitoring and diagnostic unit for adjusting the monitoring intervals for electric motor malfunctions, and in the adjustment monitoring unit, the monitoring intervals that are the periods for monitoring electric motor malfunctions, the length of the electric motor's operating history, and the importance level of the electric motor. 5. One of the electric motor diagnostic devices as specified in Claims 1 through 4, where the fault determination level of the monitoring interval provided in the monitoring and diagnostic unit is classified into three categories: normal, warning, and risk, so that the monitoring interval for observing electric motor faults is set shorter when the fault determination level is warning, and the monitoring interval is set longer when the fault determination level is risky. 6. Any of the electric motor diagnostic devices as specified in Claims 1 through 4, where the monitoring interval adjustment unit is provided in the monitoring and diagnostic unit, the monitoring interval, which is the time period for monitoring electric motor abnormalities, shall be set shorter for electric motors with long operating histories and longer for electric motors with short operating histories. 7. Any of the electric motor diagnostic devices specified in Claims 1 through 4, where the monitoring interval adjustment unit is integrated into the monitoring and diagnostic unit, the monitoring interval for observing electric motor abnormalities is set shorter for high-priority electric motors and longer for low-priority electric motors. 8. Any of the electric motor diagnostic devices as specified in Claims 1 through 4, in which the determination of malfunctions of one or more electric motors shall be made in detail by a monitoring and diagnostic unit so as to make the determination of the motor malfunctions. 9. A switching device for controlling one or more electric motors, incorporated within a plate-enclosed space, a low-voltage AC circuit, a circuit breaker for protecting the low-voltage AC circuit, electromagnetic contacts for load control, and an electronic controller including sensors for detecting electrical signals generated by the low-voltage AC circuit, and including a monitor for sensor output values and protection functions of the low-voltage AC circuit, where the switching device is characterized by the electronic controller monitoring and outputting a state before inter-phase insulation degradation or line-to-ground insulation degradation occurs in the low-voltage AC circuit, a state before the electric motor reaches a fault, and a state before the machine driven by the electric motor reaches a fault. 10. Switching devices as specified in claim 9, where the sensors shall comprise a current sensor for detecting the phase current of a low-voltage AC circuit and a zero-phase sequence current detector for detecting the zero-phase sequence current of a low-voltage AC circuit. 11. The switching device as specified in claim 9, where the sensors are incorporated, includes a current sensor for detecting the phase current of the low-voltage AC circuit and a zero-phase sequence current detector for detecting the zero-phase sequence current of the low-voltage AC circuit and a voltage output unit for the low-voltage AC circuit. 12. Any of the switching devices specified in claims 9 through 11, where the electronic controller monitors and outputs the state prior to interphase insulation deterioration or line-to-ground insulation deterioration in the low-voltage AC circuit, or the state prior to the motor reaching a fault, operates depending on the output of the zero-phase sequence current detector for detecting the zero-phase sequence current of the low-voltage AC circuit and the output of the current sensor for detecting the current of the low-voltage AC circuit or the information of the voltage output unit of the low-voltage AC circuit, or both the output of the zero-phase sequence current detector and the output of the current sensor and the information of the voltage output unit, and the electronic controller monitors and outputs the state prior to the motor-driven machine reaching a fault, depending on the output of the current sensor, or both the output of the current sensor and the information of the voltage output unit. 13. Any of the switching devices specified in claims 9 through 12, in which the electronic controller shall be incorporated with a monitoring and diagnostic unit for monitoring and diagnosing faults in the low-voltage AC circuit, electric motor, or motor-driven machine, depending on the output of the sensors; a display unit for displaying fault information when its detection by the monitoring and diagnostic unit is on interphase insulation deterioration or insulation deterioration of the line to ground in the low-voltage AC circuit, electric motor malfunction, or motor-driven machine malfunction; and a warning unit for notifying of faults when its detection by the monitoring and diagnostic unit is on interphase insulation deterioration or insulation deterioration of the line to ground in the low-voltage AC circuit, electric motor malfunction, or motor-driven machine malfunction.