JPH0775294A - Motor checker - Google Patents

Abstract

PURPOSE:To monitor the reduction in insulation resistance at all times and further automatically discriminate whether the resistance of insulation resistance is normal or not even while a motor is operating by mounting a clamp sensor to a motor cable paying attention to the fact that the difference between flow-in and flow-out current is leakage current. CONSTITUTION:Leakage current is detected while a motor is operating by a clamp sensor 1 and a microcomputer 3 compares a detection value I detected by the clamp sensor 1 with a reference value I0 which is set by a reference value setting control 2 and is stored by a microcomputer 3 and judges if it is normal or not based on the comparison result and then a speaker 5 or a flashing lamp 7 outputs a warning signal externally when the judgment result is judged to be abnormal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor checker for monitoring defective insulation resistance due to brush powder of a DC motor to warn of abnormality.

[0002]

2. Description of the Related Art Conventionally, in an AC motor such as a winding type induction motor in which both the primary side and the secondary side are star-connected, current control of the secondary side winding is performed for variable speed operation. Therefore, induction motor secondary side connection diagram as shown in FIG. 15, the secondary winding U to the rotary shaft 1, V, slip rings 2 _U which is connected to each phase of the W, 2 _V, 2 _W Is provided, and brushes 3 _U , 3 _V , and 3 _W that are in sliding contact with this slip ring are used to extract the secondary winding current output. Therefore, in the induction motor, the brushes 3 _U , 3 _V and 3 _W are constantly in sliding contact with the variable speed operation, and when the brush powder of carbon powder and copper powder is scattered and accumulated in a large amount around the shaft 1, the slip ring 2 _U , 2 _V , 2 _W short circuit occurs.

On the other hand, in the brush powder detecting device for a wire wound induction motor proposed in Japanese Utility Model Laid-Open No. 58-83975, an insulation resistance detecting circuit is provided between the neutral point of the secondary winding of the motor itself and the shaft. By providing it, it is possible to continuously and automatically monitor the decrease in insulation resistance due to the adhesion of brush powder. According to the brush dust detecting device for the winding type induction motor, as shown in FIG. 16, the neutral point slip ring 4 connected to the neutral point O of the secondary winding is provided as compared with the conventional example shown in FIG. A neutral point brush 5 which is provided on the shaft 1 and is in sliding contact with the slip ring 4 is provided, and an earth brush 6 which is in sliding contact with the shaft 1 and is grounded to the frame is provided. A DC power source is provided between the earth brush 6 and the neutral point brush 5. 7 and a DC current detector 8 for detecting the degree of brush powder adhesion. The induction motor is on the primary side,
When both secondary sides are star-connected, zero-phase current does not flow into the neutral point ground circuit, so the neutral point circuit has insulation resistance of the neutral point circuit regardless of the operating speed of the induction motor. And a DC current determined by the DC power supply 7 flows. Since this DC current increases in accordance with the degree of adhesion of the brush powder accumulated on the slip rings 2 _U , 2 _V , 2 _W, etc., the detection of the current by the DC current detector 8 may cause a short-circuit failure on the secondary side or the brush. It is possible to detect an increase in the amount of powder adhering, and by taking out as a control signal for an alarm device, etc., automatic monitoring is possible without stopping the motor operation.

However, in the above-mentioned method, the neutral point slip ring 4 connected to the neutral point O of the secondary winding,
A neutral point brush 5 which is in sliding contact with the slip ring 4, an earth brush 6 which is in sliding contact with the shaft 1 and is grounded to the frame,
Use a motor provided with a DC power supply 7 connected between the earth brush 6 and the neutral point brush 5 and a DC current detector 8 for detecting the degree of brush dust adhesion, or
In addition, there is a problem to be solved that it is necessary to modify a commercially available general-purpose motor.

In order to monitor the decrease in the insulation resistance of the motor due to the scattering of brush powder, in JP-A-3-195566, the insulation resistance of the motor driving the fire extinguishing pump is measured during automatic inspection of the fire extinguishing equipment. An insulation resistance monitoring device for an automatic fire extinguishing equipment inspection system that monitors insulation deterioration has been proposed. According to the insulation resistance monitoring device of the automatic inspection system for fire extinguishing equipment, a linear prediction equation (linear equation) or a non-linear prediction equation used for prediction from the past measured values of motor insulation resistance at the time of automatic inspection performed regularly. The coefficient of is determined, the prediction with more significance is selected, the insulation resistance measured at the next regular inspection is predicted, and if the predicted value is below the specified threshold, a pre-alarm is used to warn. By the next periodic inspection, it is possible to properly predict and judge whether the insulation resistance will fall below the alarm threshold, and in the state where the insulation resistance falls below the threshold, drive the motor and cause abnormalities such as heat generation. Can be prevented.

[0006]

However, if the insulation resistance monitoring device of the automatic inspection system for fire extinguishing equipment is applied to the measurement of the DC servo motor 11 that drives the work robot 12 used in the factory production line, As shown in FIG. 14, at the time of regular inspection, the connector 9 must be removed from the power supply, and the production line must be stopped in order to measure the insulation resistance between the connector 9 and the ground by the megatester 10. Further, if the inspection time is extended, there is a risk of causing a secondary short-circuit failure, and frequent inspection has problems such as increasing maintenance cost and lowering the operation rate of the production line.

The present invention has been made in order to solve the above problems, and attaches a leakage ammeter to a motor cable, paying attention to the fact that the leakage current of a motor is the difference between the inflow current and the outflow current of the motor. By doing so, it is possible to provide a motor checker that can constantly monitor a decrease in insulation resistance even when the motor is operating, and that can automatically determine whether the resistance value of the insulation resistance is normal or abnormal. To aim.

[0008]

As a concrete means for solving the above-mentioned problems, the present invention, as shown in FIG. 1, scatters brush powder from a difference between an inflow current and an outflow current to the motor during operation of the motor. Detecting means 51 capable of detecting leakage current due to
And a reference value setting means 52 for setting a reference value of an abnormality warning to be compared with the detection value of the detection means 51 from a grace period reaching the upper limit value of the leakage current, and a detection value and reference value setting of the detection means 51. Comparison means 53 for comparing the reference value set by the means 52 and outputting the comparison result.
And the abnormality warning means 54 for externally outputting a warning signal when the comparison result by the comparison means 53 is abnormal.

[0009]

According to the motor checker having the above-mentioned structure, the detecting means 51 detects the leak current during the operation of the motor, and the comparing means 53 sets the detection value detected by the detecting means 51 and the reference value setting means 52. When the comparison result by the comparison means 53 is abnormal, the abnormality warning means 54 outputs a warning signal to the outside.

[0010]

EXAMPLE As shown in FIG. 5, the mechanism of defective insulation resistance of a DC servo motor used for a work robot is that the brush 61 of the DC servo motor 60 rotates while being in contact with a brush 62. 63 accumulates in the brush holder 64 and the terminal portion 65. The brush scrap 63 causes a short circuit from the brush 61 to the frame 66 as indicated by an arrow, and a leakage current I3 is generated, resulting in a defective insulation resistance. The leakage current I3 can be obtained from the difference between the inflow current I1 and the outflow current I2 as shown in FIG. Therefore, by examining the relationship between the insulation resistance and the leakage current, the insulation resistance can be obtained from the leakage current.

Experimental results by the present applicant for confirming the relationship between the insulation resistance and the leakage current will be described below. First, an experimental result when a leakage current is generated only in the motor M1 will be described. As an experimental method, a resistance R1 was attached instead of the insulation resistance as shown in FIG. 7, and the insulation resistance and the leakage current were measured. As a result, it was confirmed that the insulation resistance and the leakage current have an inversely proportional relationship (R = E / I) as is known, as shown in FIG.

Next, an experimental result when the leakage currents are simultaneously generated in the motors M1 and M4 will be described. As an experimental method, as shown in FIGS. 9 (A) and 9 (B), the motor M
Insulation resistance and leakage current were measured for two types of polarities at the position of the leakage current generation in the 1-axis, the motor M4 axis, and the motors M1 and M4. As a result, by measuring the motors M1 and M4 as shown in FIG. 10, it is possible to detect both the motor M1 and the motor M4 even if a leakage current is generated. Therefore, all motors can be monitored by measuring the leakage current of the entire motor cable.

Further, in order to automatically determine whether it is normal or abnormal based on the measurement result of the leakage current, it is necessary to set a reference value for warning of abnormality. Experimental results for setting the reference value in a DC servo motor as a drive motor for the work robot will be described subsequently. As an experimental method, the resistance R1 is changed to increase the leakage current as shown in FIG. As a result, the first problem that occurs is the earth leakage breaker OF.
It was F. Then, the experiment was repeated (N = 5) to obtain data as shown in FIG. As a result, the leakage current can be tolerated up to 13.7 mA. See also FIG.
In the data of transition of operating period and leakage current shown in
The time required for inspection, cleaning, and motor replacement after the abnormality warning is 1.5 months before reaching the leakage current upper limit value of 13.7 mA, and the reference value of the abnormality warning is set to 5 mA.

Next, the structure of one embodiment of the present invention will be described with reference to the accompanying drawings. FIG. 2 is a configuration diagram showing the overall configuration of the motor checker of this embodiment. The clamp sensor 1
A clamp mechanism 1a that can be opened and closed is provided at the tip, the clamp mechanism 1a is opened, the motor cable 8 is clamped, and then the leak current I with poor insulation is detected by the hall element. A commercially available leak ammeter can be used for the clamp sensor 1. The reference value setting volume 2 has a reference value I ₀ (5 m in the present embodiment) at which the leakage current I should be judged to be abnormal.
Set A) by adjusting the scale of Volume 2. The microcomputer 3 stores the reference value I ₀ set by the reference value setting potentiometer 2, and stores the detected value I of the clamp sensor 1 and the stored reference value I ₀ according to a program stored in advance. Comparison is made, and it is determined whether normal or abnormal based on the comparison result. When it is determined that there is an abnormality, the alarm sound is generated by the speaker 5 via the amplification amplifier 4 or the alarm light is generated by the blinking lamp 7. The leakage current I detected by the clamp sensor 1 is
It is displayed on the analog ammeter 6 at any time.

Next, the operation of this embodiment having the above structure will be described with reference to the flowchart of FIG. In step S100, the reference value I is set by the reference value setting volume 2.
_{When 0} is set, the reference value I ₀ is set in step S110.
Is memorized. When the leakage current I is measured by the clamp sensor 1 in step S120, step S
At 130, the reference value I ₀ and the measured leakage current value I are compared. If the leakage current measurement value I is smaller than the reference value I ₀ ,
Returning to step S120, the leak current I is measured again by the clamp sensor 1. If the leak current measurement value I is not smaller than the reference value I _{0, the} speaker 5 generates a warning sound or the blinking lamp 7 generates a warning light in step S140. Then, the process returns to step S120 again, and the leakage current I ₀ is measured.

FIG. 4 is a perspective view showing a leak current detection state of the DC servo motor 11 used in the work robot 10. The entire motor cable 8 through which pulse-width-modulated pulse current is passed from the controller 13 to the robot body 10 is clamped by the clamp sensor 1, and the leak current of all the motors 11 is measured. Alternatively, a motor wire relay cable may be used to clamp each motor 11 and the leakage current of each motor 11 may be measured.

As described above, since the motor checker according to the present embodiment only needs to clamp the motor cable, it can be reassembled in a short time even when measuring another motor. Moreover, since a commercially available leakage ammeter can be used, it is not necessary to develop a new leakage ammeter. Further, the inspection interval of the brush of the motor is optimized, and the man-hour can be reduced.

In this embodiment, a microcomputer is used, but an electric circuit using a differential amplifier circuit or the like may be used. Further, in the present embodiment, the motor checker 20 is configured as a portable type independently of the clamp sensor 1 as shown in FIG. 4, but the meter scale of the motor checker 20 can indicate the leakage current due to the brush powder. 0 to 20 mA, and it may be a built-in type incorporated in a motor driver, a robot controller, or the like so that cutting oil or the like does not splash on the motor checker 20.

The motor checker of the present invention has the above-mentioned structure, and by attaching the clamp sensor to the motor cable, it is possible to constantly monitor the decrease of the insulation resistance even during the operation of the motor. Further, there is an excellent effect that it is possible to automatically determine whether the resistance value of the insulation resistance is normal or abnormal.

[Brief description of drawings]

FIG. 1 is a diagram corresponding to a complaint.

FIG. 2 is a schematic configuration diagram showing a motor checker of the present invention.

FIG. 3 is a flowchart showing the operation of the motor checker of the present invention.

FIG. 4 is a perspective view showing a state in which a leak current of the work robot is detected.

FIG. 5 is an explanatory diagram showing a mechanism of leakage current in a DC servo motor.

FIG. 6 is a circuit diagram showing a relationship among an inflow current, an outflow current, and a leakage current when insulation is defective.

FIG. 7 is a circuit diagram showing an experimental method for confirming the relationship between insulation resistance and leakage current.

FIG. 8 is a relationship diagram in which measurement results of insulation resistance and leakage current are plotted.

FIG. 9 is a circuit diagram showing an experimental method for confirming the relationship between insulation resistance and leakage current when a leakage current occurs in two motors at the same time.

FIG. 10 is an explanatory diagram showing insulation resistance and leakage current measurement results when a leakage current is simultaneously generated in two motors.

FIG. 11 is a circuit diagram showing an experimental method for setting a reference value for an abnormality warning.

FIG. 12 is an explanatory diagram showing a measurement result of a leakage current when the leakage breaker is OFF.

FIG. 13 is a relationship diagram showing a relationship between an operating period and a leakage current.

FIG. 14 is an explanatory diagram showing a conventional method for measuring insulation resistance.

FIG. 15 is a schematic configuration diagram showing a conventional wound-rotor induction motor.

FIG. 16 is a schematic configuration diagram showing a state in which a brush powder detecting device is provided in a conventional wire wound induction motor.

[Explanation of symbols]

1 ... Clamp sensor, 2 ... Reference value setting volume,
3 ... Microcomputer, 4 ... Amplification amplifier,
5 ... Speaker, 6 ... Analog ammeter, 7 ... flashing lamp, 51 ... detecting means, 52 ... reference value setting means,
53 ... Comparison means, 54 ... Abnormality warning means.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location H02K 11/00

Claims (1)

[Claims] 1. A detection unit capable of detecting a leakage current due to scattering of brush powder from a difference between an inflow current and an outflow current to the motor during operation of the motor, and an abnormality warning standard to be compared with a detection value by the detection unit. Reference value setting means for setting a value from the grace period of reaching the upper limit value of the leakage current, and comparison means for comparing the detection value by the detection means and the reference value set by the reference value setting means and outputting the comparison result. And an abnormality warning unit that outputs a warning signal to the outside when the comparison result by the comparison unit is abnormal, and the motor checker is provided.