JPS6385380A - Method for detecting trouble of motor - Google Patents

Abstract

PURPOSE:To certainly detect the trouble of a motor and to clearly distinguish between a short circuit, open phase and earth, by successively applying voltage not rotating the motor and detecting the input circuit of an inverter device. CONSTITUTION:A converter device 3 is connected to a commercial AC power source 1 through a power source switch 2 and a three-phase induction motor 6a is connected to an inverter device 5. When trouble is detected, a base drive circuit 10 performs the ON/OFF control of the power transistor constituting the inverter device 5 on the basis of a microcomputer 9. A pattern check circuit 11 checks the current flowing corresponding to the ON/OFF state of the transistor from the voltage between both terminals of a current divider 7 and returns the checking result. A display device 12 allow the display lamps corresponding to a short circuit, open phase and earth to light of the basis of said result.

Description

Detailed Description of the Invention [Object of the Invention] (Industrial Application Field) The present invention is directed to a failure detection method for a motor driven by an inverter device, which detects at least one of a short circuit, an open phase, and a ground fault. Regarding the method.

(Prior Art) In air conditioners, an inverter device is often used to operate a compressor driving electric motor (hereinafter simply referred to as an electric motor) under capacity control. To detect failures such as short circuits, open phases, and ground faults in the motor, for example, as shown in Figure 8,
A shunt 7 was inserted on the input side of an inverter device 5 that supplies alternating current power to an electric motor 6, and the overcurrent detected by an overcurrent detector 8 was used for evaluation.

(Problems to be Solved by the Invention) The conventional electric motor failure detection method described above evaluates only the overcurrent of the inverter device, and therefore cannot distinguish between a failure of the inverter device and a failure of the electric motor.

Further, even if it is determined that the motor has failed, it is not possible to distinguish between a short circuit, an open phase, and a ground fault, making it difficult to take measures such as, for example, protecting power transistors forming an inverter device from a ground fault.

The present invention has been made to solve the above-mentioned problems, and aims to provide a motor failure detection method that can reliably detect failures of electric motors and clearly distinguish between short circuits, open phases, and ground faults. purpose.

[Structure of the invention]

(Means for Solving the Problems) The present invention provides a failure detection method for a motor that detects at least one of a short circuit, an open phase, and a ground fault in a motor driven by an inverter device, using the inverter device. A voltage that does not cause the motor to rotate is sequentially applied to lines or lines connecting the inverter device of the lever and the electric motor, and an input terminal of the inverter device is detected, and the electric motor changes depending on whether the detected current is excessive or insufficient. This system is characterized by logically determining short circuits, open phases, and ground faults.

(Function) When driving an electric motor using an inverter device, it is extremely easy to generate a voltage that does not cause the electric motor to rotate between the lines or lines connecting the inverter device and the electric motor. If a voltage is applied between the connection lines while the motor is short-circuited, the input current of the inverter device will be significantly larger than that during normal operation. Therefore, a short circuit in the motor can be detected by sequentially applying a voltage that does not cause the motor to rotate between the connection lines using the inverter device and determining whether an excessive current flows through the inverter device.

Next, if a voltage is applied between each connection line in a state where the motor has an open phase, there is a phase in which the input current of the inverter device becomes approximately zero. Therefore, phase loss in the motor can be detected by sequentially applying a voltage that does not cause the motor to rotate between each connection line using an inverter device and determining whether the input current of the inverter device becomes substantially zero. Can be done.

On the other hand, if the motor is grounded, for example, if an electrode that is slightly different from the ground potential, such as the negative electrode of a DC power source, is connected to each connection line (this invention is also referred to as voltage application). ) A much larger current flows than that under normal conditions. Therefore, a ground fault in the motor can be detected by applying a voltage that does not cause the motor to rotate to each connection line via the inverter device and determining whether the current value becomes excessive.

The present invention detects motor failure according to these principles.

(Embodiment) FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention. In the figure, a converter device 3 is connected to a commercial AC power source 1 via a power switch 2, a smoothing capacitor 4 and an inverter device 5 are connected to the output side of the converter device 3, and an inverter device 5 is connected to the output side of the converter device 3. A three-phase induction motor (hereinafter simply referred to as a motor) 6a is connected to the device 5.

In order to detect a failure of the motor 6a, a shunt 7 is inserted into the input circuit of the inverter device 5, and the voltage across the shunt 7 is input to the microcomputer 9. An operation signal for the power switch 2 is also input to the microcomputer 9. In addition, the base drive circuit 10 that controls on/off the power transistors constituting the inverter device 5 is checked based on the output of the microcomputer 9, and the currents flowing corresponding to the on/off states of these transistors are checked.
A pattern check circuit 11 that sends back the results, and an indicator 12 that turns on a corresponding indicator light when there is an open phase, short circuit, or ground fault based on the check results are provided.

The operation of this embodiment configured as described above will be explained below with reference to FIGS. 2 to 7.

First, when the power switch 2 is closed, the converter device 3
rectifies and outputs the AC voltage of the AC power source 1, and this rectified output is closed by the capacitor 4 and supplied to the inverter device 5. When the electric motor 116a is operated under capacity control, a control circuit (not shown) provides a pulse signal to the base drive circuit 10 to control the onverter device 5, but the detailed operation thereof is not directly related to the present invention and will not be described.

On the other hand, immediately after the power switch 2 is closed, the microcomputer 9 delays the operation of the electric motor 6a for a short period of time, and during this time, detects a failure of the electric motor 6a by giving a pulse signal to the base drive circuit 10.

Here, the inverter device 5 has power transistors (hereinafter simply referred to as transistors) 01-
G6 is connected by Graetz, and the transistor Gl
, G4 are connected to the U-phase winding of the motor 6a, and the transistors G2. The mutual junction point of G5 is connected to the V-phase winding of the motor 6a, and the transistor G3. The mutual junction point of G6 is the electric motor 6a
Suppose that the W-phase windings are connected to the respective W-phase windings.

Then, in order to detect a short circuit in the motor 6a, the microcomputer 9 converts the transistor G1 into a
, 05, transistors G1 and 66, and transistors G2 and 06, respectively, are applied to the base drive circuit 10 in pairs to turn on signals in sequence. At this time, if there is a short circuit between the V-phase winding and the W-phase winding of the motor 6a, the current IDC shown in FIG. 3 flows through the inverter device 5, and a digital signal corresponding to this waveform is sent to the pattern check circuit 11. added to. Pattern check circuit 11
determines that the current when transistors G2 and 06 are turned on exceeds the threshold η1, and sends back a signal to the microcomputer 9 indicating that there is a short circuit between the V-phase winding and the W-phase winding. do.

Next, in order to detect an open phase in the motor 6a, the microcomputer 9 detects transistors G1 and 05, transistors G1 and 06, transistors G2 and 0, as shown in FIG.
A signal is applied to the base drive circuit 10 so that the base drive circuits 6 are sequentially turned on in pairs. At this time, the electric motor 6a
Assuming that the W-phase winding of the inverter 5 has an open phase as shown in FIG. A current IDC flows that gradually increases due to the inductance, and other than this, the current IDC is substantially zero. The pattern check circuit 11 determines that the current when the transistors G1 and 66 and the transistors G2 and 66 are turned on is smaller than the threshold value η2, and outputs a signal indicating that the W-phase winding has an open phase. It is sent back to the microcomputer 9.

Next, in order to detect a ground fault in the electric motor 6a, the microphone computer 9 detects a ground fault in the electric motor 6a by using transistors G4. G
5. A signal is applied to the base drive circuit 10 so that G6 is sequentially turned on. At this time, if the W-phase winding of the motor 6a has a ground fault as shown in FIG. 6, even if transistors G4 and G5 are turned on, only a small amount of current flows due to the inductance of the winding, but the transistor G6 is turned on. A current IDC that becomes excessive only when the current IDC is increased flows to the input side of the inverter device 5, and a signal corresponding to this is applied to the pattern check circuit 11. The pattern check circuit 11 determines that the current when the transistor G6 is turned on is larger than the threshold value η3, and sends back to the microcomputer 9 a signal indicating that the W-phase winding is grounded.

Here, the microcomputer 9 turns on the corresponding lamp of the indicator 12 depending on which of the above-mentioned short circuit, open phase, or ground fault has occurred.

After the failure detection operation is completed, the microcomputer 9 issues a command to a control circuit (not shown) to start normal operation. However, if a short circuit, open phase, or ground fault is detected, the operation is stopped. Does not generate commands. This also solves the problem that the failure spreads to the transistors 01 to G6 due to starting the operation of the inverter device when the electric motor is abnormal.

Note that if the inverter device 5 has failed during the above-described failure detection, an unexpected current waveform pattern will be obtained, making it easy to distinguish between the inverter device failure and the electric motor failure.

Furthermore, although the above embodiment describes the case where all of the short circuit, open phase, and ground fault of the motor are detected, it is of course possible to configure the system to detect any one or two of these. be.

Further, in the above embodiment, the transistor G1. G2゜05,
Although the energization time of G6 is controlled, the present invention is not limited to this, and the voltage/frequency ratio is two-phase voltages that are equal to each other during normal energization, or the voltage/frequency ratio is lower than that during normal operation. A fairly small three-phase voltage may be used, and in short, it is sufficient to sequentially apply voltages that do not cause the motor to rotate.

【Effect of the invention〕

As is clear from the above description, according to the present invention,
This has the effect of being able to reliably detect motor failure and clearly distinguish between short circuits, open phases, and ground faults.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of an apparatus for implementing the present invention, FIGS. 2, 4, and 6 are wiring diagrams for explaining various failures of the electric motor, and FIGS. FIG. 7 is a time chart for explaining the operation of detecting various failures of the electric motor by the above device, and FIG. 8 is a block diagram showing an example of the configuration of the device employing the conventional failure detection method. 5... Inverter device, 6a... 3-phase induction motor,
7... Flow divider, 9... Micro combinator, 10
...Base drive circuit, 11...Pattern check circuit, 12...Display device. Applicant's agent Sato-Omo 2 Figure G6 Color 3 Figure also 4 Figure death 5 Figure horse 6 Figure Shiba 7 Figure procedure correction disease October 29, 1985

Claims (1)

[Claims] 1. Short circuit of an electric motor driven by an inverter device;
In the motor failure detection method of detecting at least one of an open phase and a ground fault, the inverter device is used to sequentially apply a voltage at which the motor does not rotate between lines or lines connecting the inverter device and the motor. A failure detection method for a motor, characterized in that the input current of the inverter device is detected at the same time as the current is applied, and a short circuit, an open phase, and a ground fault of the motor are logically determined according to the detected excess or deficiency of the current. 2. When the motor is a three-phase motor, the inverter device outputs two-phase voltages whose voltage/frequency ratios are equal during normal operation, or outputs three-phase voltages whose voltage/frequency ratios are considerably smaller than during normal operation. 2. A method for detecting a failure in an electric motor according to claim 1, wherein the voltage is output as follows.