JP4199559B2 - Three-phase induction motor insulation deterioration monitoring device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an apparatus that automatically measures insulation resistance of a three-phase induction motor mounted on a machine tool or the like and monitors insulation deterioration.
[0002]
[Prior art and its problems]
In recent years, many machine tools and the like are equipped with a servo motor (three-phase induction motor). This is because the servo motor is an important element for realizing automation and precision machining. However, on the other hand, a great deal of cost is required for maintenance of the servo motor, which is a precision instrument. In general, since a large amount of cutting oil is used in a machine tool, the oil may enter the motor, and the insulation performance deteriorates due to the penetration of the oil, resulting in malfunction or burning of the motor. Therefore, it is necessary to periodically inspect the motor for deterioration of insulation.
[0003]
As a method for inspecting the insulation deterioration, there is a method of measuring the insulation resistance with a megger (insulation resistance meter) after removing the wiring between the motor and the power source. However, since one machine tool is usually equipped with three or more servo motors (three axes), the inspection method requires a considerable man-hour for inspection per machine tool. In particular, when a large number of machine tools are installed in one factory, a great deal of labor and human costs are required.
[0004]
Therefore, devices as described in Patent Documents 1 and 2 below are known as devices for monitoring insulation deterioration of a motor.
[0005]
[Patent Document 1]
Japanese Examined Patent Publication No. 6-40724 (page 3-5, Fig. 1)
[Patent Document 2]
JP 2001-141795 A (page 3-6, FIG. 1)
[0006]
In the invention of Patent Document 1, one of the motor windings is disconnected from the power source and connected to another measurement circuit, thereby measuring the insulation resistance of the winding with respect to the ground. In the above-mentioned apparatus, since the operation of the switch circuit requires manpower and the measurement is performed during the operation of the motor, the influence of noise is large and there is a risk of erroneous detection. Moreover, since installation work of the switch circuit for interrupting | blocking a power wire between a power supply and a motor is needed, time and cost start. Furthermore, in a machine tool, if one phase is disconnected from the power source, the motor cannot be operated normally.
[0007]
In the invention of Patent Document 2, the insulation resistance is measured by sending a high-frequency pulse to the motor by the power converter when the motor is stopped. However, since this apparatus uses high-frequency pulses for measurement, a complicated circuit is required. Moreover, in a machine tool in which the machining conditions and the surrounding environment change, a leakage occurs in addition to the motor, and it is not possible to accurately measure the leakage of the motor.
[0008]
The present invention has been made to solve such a problem, and by automatically monitoring insulation deterioration of a three-phase induction motor in a machine tool or the like and displaying the inspection result to the outside, the inspection man-hour is remarkably increased. An object is to provide a device that can be reduced.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, a monitoring device according to the present invention is a device that monitors insulation deterioration of a three-phase induction motor to which driving power from a three-phase AC power supply is supplied via a motor control device that performs frequency conversion. Detecting means for detecting ON / OFF of whether or not power is supplied to the motor, measuring means for measuring the insulation resistance of the motor, and inspection connected to the three-phase power line and ground of the motor, respectively A path of power supplied between each three-phase power line and the ground from an inspection power source inserted between the power line for power supply and the measuring means and provided separately from the three-phase AC power source The switching circuit to be selected and one of the three-phase power lines and the ground based on the output from the detection means only when the motor is OFF when the detection means detects the OFF of the motor Between An inspection voltage is applied from the inspection power supply, and an insulation resistance between the power supply line and the ground is measured by the measuring means, and this measurement is controlled by the switching circuit to connect each three-phase power supply line to the ground. Measurement control means for sequentially performing the measurement, a determination means for comparing the measured insulation resistance value with a preset threshold value to determine the degree of deterioration of the motor, and the result of the determination to the outside And display means for displaying.
[0010]
According to the present invention, ON / OFF of whether or not electric power is supplied to the motor is detected by the detecting means, and the insulation resistance is automatically measured based on the OFF output from the detecting means. At this time, the measured insulation resistance value is compared with a preset threshold value to determine the degree of motor insulation deterioration.
[0011]
In the present invention, a storage unit capable of storing a plurality of insulation resistance values measured by the measurement unit, and a signal is transmitted to the measurement control unit at regular time intervals while the power supply to the motor is OFF. It is preferable to further comprise a timer. With this configuration, if the measurement control unit controls the measurement unit so that the measurement is performed a plurality of times while the motor is stopped and the measurement result is stored in the storage unit in time series, the operator can record the history of the plurality of measurement results. By referring to the above, it is possible to obtain information useful for motor management, such as motor deterioration characteristics and progress patterns.
[0012]
In the present invention, the apparatus further comprises storage means capable of storing a plurality of insulation resistance values measured by the measurement means, and performs the measurement a plurality of times while the power supply to the motor is OFF. The control means controls to store the measured insulation resistance value in the storage means, and the determination means performs the determination based on a plurality of measurement results stored in the storage means. May be. According to this configuration, since the determination of deterioration is performed based on a plurality of measurement results, determination accuracy and reliability are improved as compared with a case where determination is performed based on a single measurement result.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 shows the monitoring device 1 for measuring the insulation resistance of a motor (three-phase induction motor) M. The monitoring device 1 includes three-phase power lines 4 and 6 that connect the ground 2 of the motor M and the motor M to the motor control device 100 via four power lines 12, 14, 16, and 18 for inspection. , 8 are connected to each other.
The motor control device 100 controls the driving of the motor M by converting the frequency of the power from the three-phase AC power supply 101 and supplying the driving power to the motor M.
[0014]
The monitoring device 1 includes a microcomputer 10, a switching circuit 20, first detection means 30, and an inspection power source 5. The power lines 12, 14, 16, 18 are connected to the external connection terminals 20a to 20d of the switching circuit 20, respectively. The inspection power supply 5 is connected to the external connection terminal 20 e of the switching circuit 20.
[0015]
As will be described later, the switching circuit 20 is connected between the ground 2 and the three-phase power lines 4, 6, 8 from the inspection power supply 5 through the power lines 12, 14, 16, 18. The path of the power applied to is selected.
As shown in FIG. 2, the switching circuit 20 has four contactless relays 21 to 24 made of a photocoupler or the like. Each of the relays 21 to 24 is inserted in each of the power lines 12 to 18. One end of the input end of each of the relays 21 to 24 is connected to the external connection terminal 20f of the switching circuit 20, and the other end is connected to the terminals C1 to C4 of the microcomputer 10, respectively. The external connection terminal 20f is connected to an external power source (not shown) or the inspection power source 5 as a driving power source.
The power lines 14, 16, and 18 are connected to the external input terminal C5 of the microcomputer 10.
[0016]
The microcomputer 10 includes a CPU (determination unit) 11, a ROM 13, a RAM (storage unit) 15, and a measurement circuit (measurement unit) 17. The microcomputer 10 is connected to a display means 41, a setting device 42 and a timer 43 through an interface (not shown).
The measurement circuit 17 measures a signal input to the external input terminal C5 described later, and is mounted on the substrate of the microcomputer 10.
[0017]
The CPU 11 includes a control unit (measurement control unit) 11a and a calculation unit (measurement unit) 11b.
The control unit 11a controls the operation of the switching circuit 20 based on an output from the first detection means 30 described later, that is, selects an arbitrary terminal among the terminals C1 to C4, and selects the selected terminal. By applying a voltage to, the ON / OFF of each of the relays 21 to 24 is controlled, and the operation of the measurement circuit 17 is controlled.
The computing unit 11b constitutes an insulation resistance measuring means together with the measuring circuit 17. The calculation unit 11 b calculates the insulation resistance of the motor M from the signal measured by the measurement circuit 17.
After completing the calculation of the insulation resistance, the CPU 11 determines the degree of insulation deterioration of the motor M and outputs the determination result to the display means 41.
[0018]
In the ROM 13, threshold values serving as a reference for the determination, for example, first to third threshold values SH <b> 1 to SH <b> 3 shown in FIG. The setting of this threshold value can be arbitrarily changed by the setting device 42.
As shown in FIG. 3B, the RAM 15 stores the insulation resistance values and the like in the measurement performed by the CPU 11 a plurality of times in time series.
[0019]
Detection means The first detection means 30 shown in FIG. 1 detects ON / OFF whether or not the drive power from the three-phase AC power supply 101 is supplied to the motor M via the motor control means 100. To do. As shown in FIG. 2, the first detection means 30 includes three photocouplers 31-33. The light emitting elements of the photocouplers 31 to 33 are connected to the power lines 16 and 18 via the power line 14 and the power line 14. On the other hand, one end of the light receiving element of each of the photocouplers 31 to 33 is connected to the terminal C6 of the microcomputer 10, and the other end is grounded. The photocoupler 31 monitors between the external connection terminals 20b and 20c, the photocoupler 32 is between the external connection terminals 20c and 20d, and the photocoupler 33 is between the external connection terminals 20d and 20b. It is something to monitor. Therefore, as the power supply to the motor M is turned on and off, the photocouplers 31 to 33 are turned on and off, so that the potential of the terminal C6 changes. Thereby, the first detection means 30 detects ON / OFF of the power supply to the motor M.
[0020]
Next, the operation of the monitoring apparatus 1 will be described mainly using the flowchart and timing chart of FIG.
When the power supply to the motor M is ON, that is, while the motor M is being driven, the control unit 11a of the CPU 11 indicates that the relays 22 to 24 of the switching circuit 20 in FIG. 2 are ON and the relay 21 is OFF. And the switching circuit 20 is held in a standby state. As a result, while the power supply to the motor M is ON, at least one of the photocouplers 31 to 33 of the first detection unit 30 is ON, so the potential of the terminal C6 is zero, that is, Held at a low level. While the low level is maintained, the control unit 11a keeps the relay 21 OFF so that the inspection voltage from the inspection power supply 5 is not applied to the motor M.
[0021]
Now, when the power supply to the motor M is turned off, that is, when the motor M is stopped, the photocouplers 31 to 33 of the first detection means 30 are all turned off. Therefore, as shown in FIG. 4A, the potential of the terminal C6 changes from the low level to the high level. Using the change in the potential of the terminal C6 as a trigger, the control unit 11a starts measuring the insulation resistance according to the flowchart of FIG. 4B.
[0022]
First, in step S1, the control unit 11a selects a winding (not shown) of the motor M to be measured. For example, when the winding connected to the U-phase power supply line 4 is selected, the control unit 11a turns on the relays 21 and 22 of the switching means 20 and turns off the relays 23 and 24 in FIG. To control. As a result, the inspection voltage is not applied to the other two-phase windings, and the inspection voltage is applied only to the windings connected to the U-phase power supply line 4. When the switching of the relay is completed, the process proceeds to step S2.
[0023]
In step S2, the controller 11a measures the insulation resistance with respect to the ground of the selected winding. The inspection voltage from the inspection power supply 5 connected to the external connection terminal 20e of the switching circuit 20 is as follows: relay 21 → power line 12 → earth 2 → winding → U-phase power supply line 4 → power line 14 → relay 22 → It is applied to the motor M through a path called an external input terminal C5. As a result, a leakage current is generated.
Note that, from the viewpoint of malfunction and measurement accuracy, the inspection power source 5 is preferably a direct current, alternating current, or pulse power source with a small electromotive force of about several volts.
[0024]
The leakage current flows to the ground point through the resistor R0 of FIG. At this time, the control unit 11a of the CPU 11 controls the measurement circuit 17 to measure a signal input to the external input terminal C5, for example, a voltage applied to the resistor R0. The measurement circuit 17 outputs the measured signal to the calculation unit 11b of the CPU 11. The computing unit 11b calculates an insulation resistance value from the following equation (1) based on this signal.
R _A = (V _A −V _S ) / I _L (1)
Here, R _A insulation resistance, V _A is applied testing voltage, V _S signal measured at the external input terminal C5, the I _L is the leakage current.
The leakage current I _L can be obtained from the following equation (2).
I _L = V _S / R _S (2)
Here, R _S is the resistance value of the resistor R0.
Therefore, the insulation resistance value can be calculated from the above equations (1) and (2).
[0025]
A resistor R1 in FIG. 2 is a resistor for protecting the monitoring device 1 from damage when the driving power of the motor M is applied to the monitoring device 1 due to malfunction. The resistor R2 is a driving power detection resistor provided so that the first detection means 30 detects only the driving power of the motor M and does not operate due to the leakage current.
[0026]
When the measurement (calculation) of the insulation resistance is completed in step S2, the process proceeds to step S3. In step S <b> 3, the CPU 11 reads out a threshold value that is a criterion for determination from the ROM 13, and compares the threshold value with the calculated insulation resistance value to determine insulation deterioration. Since the insulation resistance value of each winding of the motor M is normally 100 MΩ or more, for example, the first to third threshold values are set to 200 MΩ, 100 MΩ, and 2 MΩ, respectively, as shown in FIG. If the measured insulation resistance value is 200 MΩ or 100 MΩ or more, the CPU 11 determines “no problem” and outputs the determination result to the display means 41.
[0027]
Similarly, when the measured insulation resistance value is smaller than 100 MΩ and 2 MΩ or more, the CPU 11 determines that “degradation is in progress” and checks the motor M or replaces the motor. Is output to the display means 41.
Further, when the measured insulation resistance value is smaller than 2 MΩ, the CPU 11 determines that “should be replaced immediately” and displays a warning to that effect on the display means 41.
These determination results may be displayed after the determination by the CPU 11 or displayed on the display means 41 when the operator restarts the motor M or by the operator's operation. You may make it do.
[0028]
After step S3, in step S4, if the measurement and deterioration determination of the two-phase insulation resistance other than the U phase are not performed, the process branches to NO, and then the V phase and the W phase are sequentially similar. The insulation resistance measurement and deterioration determination are repeated (steps S1 to S4). That is, for the windings connected to the V-phase power line 6, the relays 21 and 23 in FIG. 2 are turned on and the relays 22 and 24 are turned off, and the windings connected to the W-phase power line 8. Turns on the relays 21 and 24 and turns off the relays 22 and 23.
[0029]
When the deterioration determination for all the windings is completed, the process branches to YES in step S4 and proceeds to step S5. In step S5, the control unit 11a controls the switching unit 20 to return to an initial state, that is, a state in which the relay 21 is OFF and the relays 22 to 24 are ON. When the operation in step S5 is completed, the monitoring operation for the insulation deterioration of the motor M is terminated.
[0030]
By the way, the monitoring device 1 may perform the measurement of the insulation resistance and the deterioration determination a plurality of times while the power supply to the motor M is OFF. In this case, the control unit 11a of the CPU 11 performs the measurement and determination based on a signal input from the timer 43 (FIG. 1) at a constant time interval, and as shown in FIG. The plurality of insulation resistance values thus made are stored in the RAM 15 in time series. If a history made up of a plurality of measurement results as shown in FIG. 3B can be displayed on one screen of the display means 41, the operator can check the history at a glance, which is useful for motor management. Information can be obtained.
[0031]
Further, the plurality of measurements may be continuously performed a plurality of times when the power supply to the motor M is turned off. The CPU 11 may perform the determination based on the plurality of measurement results (insulation resistance values) regardless of whether the measurement is performed continuously or discontinuously. For example, the determination may be made by comparing an average value of a plurality of measurement results with the threshold value, and the insulation resistance value having the smallest value among the plurality of measurement results is compared with the threshold value. Then, the determination may be performed.
[0032]
In the description of the embodiment, the case where there is one motor M has been described in order to simplify the description. However, the present invention can also be applied to a machine tool including a plurality of motors M. When monitoring the insulation deterioration of a machine tool provided with a plurality of motors M, when one or more of the plurality of motors M are stopped, or the power to the machine tool itself is turned off. In any of the cases, the present apparatus 1 monitors the insulation deterioration of each motor M by the following configuration and operation.
[0033]
(1) The switching circuit 20 and the first detection means 30 are provided for each motor M, and each motor M is monitored for power ON / OFF. When one or more motors M are stopped, the stopped motor M is inspected for insulation deterioration as described above. By doing so, it is possible to determine the deterioration of the motor M that is stopped at any time during the operation of the machine tool.
[0034]
(2) The switching circuit 20 is provided for each motor M, and second detection means 40 is provided as shown in FIG. The second detection means 40 is connected to the motor control device 100, for example, and detects ON / OFF of the main power supply of the machine tool itself and transmits a signal to the CPU 11.
When the CPU 11 receives the OFF output from the second detection means 40, the CPU 11 sequentially measures and determines the insulation deterioration for each motor M. By doing so, when the main power supply of the machine tool is OFF, that is, when all of the plurality of motors M are stopped, the deterioration inspection of each motor M can be sequentially performed.
[0035]
When there are a plurality of motors M, the monitoring device 1 preferably includes a switching device (not shown) that selects the switching circuit 20 corresponding to the motor M to be inspected.
[0036]
As described above, the preferred embodiments have been described with reference to the drawings. However, those skilled in the art will readily understand various changes and modifications within the obvious scope by looking at the present specification.
For example, the signal to be measured by the external input terminal C5 may be directly measured leakage current I _L in place of the voltage applied to the resistor R0.
Further, from the viewpoint of noise and operating speed, the switching circuit 20 and the first detection means 30 use a contactless relay such as a photocoupler, but a contacted relay such as an electromagnetic relay may be used. However, when a contact relay is used, it is necessary to add an overcurrent / overvoltage protection circuit. Further, the detection means is not necessarily configured by a circuit as in the above-described embodiment, and may be configured by an electronic device such as a sensor.
The inspection power supply 5 may be a built-in power supply, or another external power supply may be used. However, when a separate power supply is used, it is necessary to use a stabilized power supply and to change the resistance value of the resistor R0 and the measurement circuit 17 to necessary specifications as appropriate.
Accordingly, such changes and modifications are to be construed as within the scope of the present invention as defined by the claims.
[0037]
【The invention's effect】
As described above, according to the present invention, the detection means is provided, and the insulation resistance is automatically measured when the motor is stopped by detecting ON / OFF of the power supply to the motor by the detection means. Periodic motor deterioration inspection can be made unnecessary. Accordingly, the number of inspection steps can be remarkably reduced, and since the insulation resistance is measured when the power supply to the motor is OFF, it is possible to perform measurement with less noise and high accuracy.
[0038]
In addition, if this monitoring device is attached by connecting the motor to the motor control device with a three-phase power line and a motor ground, the time and cost can be reduced because no installation work is required. be able to.
[0039]
In addition, if a timer for transmitting signals at regular time intervals and a storage means for storing a plurality of measurement results in time series are provided, a plurality of measurements are performed while the motor is stopped, and the plurality of measurement results are stored in time. Can be stored in series. If the history consisting of a plurality of measurement results can be displayed in time series on the display means, the operator can refer to this history, which is useful for motor management, such as motor deterioration characteristics and progress patterns. Information can be obtained.
[0040]
Further, if a storage means for storing a plurality of insulation resistance values is provided and the determination is performed based on the results of a plurality of measurements, the accuracy and reliability of the determination can be further improved.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a schematic configuration showing an embodiment of the present invention.
FIG. 2 is a circuit diagram showing an example of the switching circuit.
FIG. 3A is a chart showing a threshold value and a method for determining deterioration, and FIG. 3B is a chart showing an example of information stored in a storage unit.
FIG. 4A is a timing chart showing the timing when the monitoring apparatus starts measurement, and FIG. 4B is a flowchart showing the operation of the monitoring apparatus.
[Explanation of symbols]
1: Monitoring device 2: Grounding 4, 6, 8: Three-phase power supply line 5: Power supply for inspection 12, 14, 16, 18: Power line 11: CPU (determination means)
11a: Control unit (measurement control means)
11b: Calculation unit (measuring means)
17: Measuring circuit (measuring means)
15: RAM (storage means)
20: switching circuit 30: first detection means 40: second detection means 41: display means 43: timer 100: motor control device 101: three-phase AC power supply M: three-phase induction motor

Claims (3)

In a device that monitors insulation deterioration of a three-phase induction motor to which driving power from a three-phase AC power supply is supplied via a motor control device that performs frequency conversion,
Detecting means for detecting ON / OFF whether power is supplied to the motor;
Measuring means for measuring the insulation resistance of the motor;
The three-phase power line of the motor and an inspection power line connected to the ground and the measuring means are inserted between the three-phase AC power source and the three-phase AC power source. A switching circuit that selects a path of power supplied between the power line and the ground;
The inspection is performed between one of the three-phase power lines and ground, based on the output from the detection means, only when the detection means detects that the motor is OFF. An inspection voltage is applied from the power source for power, and the insulation resistance between the power line and the earth is measured by the measuring means, and this measurement is controlled between the three-phase power lines and the ground by controlling the switching circuit. Measurement control means for sequentially performing;
A determination means for comparing the measured insulation resistance value with a preset threshold value to determine the degree of deterioration of the motor;
Display means for displaying the determination result to the outside;
A three-phase induction motor insulation deterioration monitoring apparatus characterized by comprising: In claim 1 ,
Storage means capable of storing a plurality of insulation resistance values measured by the measurement means; and a timer for transmitting a signal to the measurement control means at regular time intervals while the power supply to the motor is OFF. Prepared,
Based on the signal from the timer, the measurement control unit performs the measurement a plurality of times, and the measurement control unit controls the storage unit to store a plurality of values of the insulation resistance measured at each time in a time series,
A three-phase induction motor insulation deterioration monitoring apparatus capable of displaying a history of a plurality of measurement results stored in the storage means in time series on the display means. In claim 1 ,
A storage unit capable of storing a plurality of insulation resistance values measured by the measurement unit;
While the power supply to the motor is OFF, the measurement control unit performs the measurement a plurality of times, and the measurement control unit controls the storage unit to store the value of the insulation resistance measured at each time,
The determination unit is a three-phase induction motor insulation deterioration monitoring device that performs the determination based on a plurality of measurement results stored in the storage unit.

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