JPS5928149B2 - Motor operation monitoring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an operation monitoring device for an electric motor, and in particular has a function of inspecting cable breakage, a function of inspecting a cable disconnection device connected to a motor circuit, and a function of monitoring the normal operating state of the motor. The present invention relates to an operation monitoring device for an electric motor.

There are cases where multiple electric motors are connected in parallel to the same power source to perform uniform speed acceleration operation.

When performing such constant speed acceleration operation, it is necessary to intensively monitor the operating state of each electric motor, determine the constant speed acceleration rate and operate the motor, and at the same time promptly detect any abnormality in the rotation speed of the motor. Conventionally, a method has been used to determine the voltage and frequency increase pattern in advance and accelerate according to this pattern, but due to differences in the characteristics of each motor and differences in the load connected to the motor, There was a risk that some motors would fall out of uniform speed operation. If a fallen electric motor comes out, it will be detected immediately and
It is necessary to disconnect it from the constant speed operation circuit so that it does not interfere with operation of other motors. In addition to monitoring the operating status of these electric motors, it is also necessary to check the functionality of the sheath disconnection device, including the disconnector, connected to the motor circuit, and check for cable breaks.

With these inspection functions, if a failure occurs in the main circuit such as the motor or cable in a constant speed operation circuit, the faulty circuit can be quickly disconnected using a disconnection device, and other healthy circuits can be disconnected. It is possible to prevent accidents from spreading to other areas. It is preferable that the monitoring of the operating state of the electric motor, the function check of the shearing device, and the cable breakage check are functionally linked and performed in the same or single operation, rather than being performed separately. F. In view of the above points, the present invention provides a motor operation monitoring device that can effectively monitor the operating state of the motor, inspect the shear breakage device, and inspect the cable breakage by the same or a single operation. With the goal. An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, reference numeral 1 denotes a three-phase AC power supply, and a motor 3 is connected to this power supply 1 via a shear cutter 2. In actual constant speed operation, this power supply 1 is equipped with disconnection devices 20 and 200, respectively.
A large number of electric motors (for example, 250 motors) 30, 300, . . . are connected in parallel via .

The cutoff device 2 includes transistors 4R, 4S, 4T connected to the three-phase main circuits R, S, T, respectively, and diodes 4DR, 4DS, 4DT connected in antiparallel to the transistors. 0N, 0 for 4R, 4S, 4T
A control signal for the FF is given. 6R and 6T are current transformers inserted into the main circuits of the R and T phases, and the secondary outputs of the current transformers 6R and 6T are signals rectified by the three-phase full-wave rectifier circuit 7. It is given to the control circuit 5 as a failure detection signal.

15 is an operation monitoring device that divides the output voltage of the rectifier circuit 7 with voltage dividing resistors 8 and 9, and detects the voltage across the resistor 9 with a detection device 1.
7 to detect.

The current f of the R, S, and T phases of the three-phase main circuit is detected by the detection device 17.
The current waveform and frequency are detected. Furthermore, this detection device 1
The output signal of 7 is judged by a judgment circuit 16, and 0N, 0FF signals are outputted to the control circuit 5 based on the output signal of the judgment circuit 16. Next, the operation of the motor operation monitoring device having the above configuration will be explained.

0 from the control circuit 5 to each phase transistor 4R, 4S, 4T
When the N signal is applied, the transistors 4R, 4S, and 4T become conductive, and power is supplied from the power supply 1 to the motor 3, and starting and acceleration begin. When a failure occurs in the main circuit or the motor 3, the fault current is detected by the current transformers 6R and 6T, and the control circuit 5 gives the transistors 4R, 4S, 4Ti (.0FF signal) to disconnect the circuit. To check for cable breakage, the detection device 17 of the operation monitoring device 15 detects the secondary output voltages of the current transformers 6R and 6T. In this case, the voltage across the resistor 9 becomes a three-phase full-wave rectified waveform as shown in Figure 2a. As shown in Figure b, the single-phase full-wave rectified waveform can be used to detect open phase and cable abnormality.The waveform detection by the detection device 17 also indicates that current is flowing normally to the shearing device 2. Furthermore, when the operation monitoring device 15 instantaneously applies an 0FF signal for approximately 0.2 seconds to the control circuit 5 of the shearing breaker 2, the first switch 14 becomes 0FF and the power from the power supply 1 is turned off. The supply of electric power is stopped.This causes the motor to become a generator, and a reverse induced voltage is generated between the R, S, and T phases.
Next, the second switch 13 closes, allowing current to flow from the motor side through the three-phase reactor 12. Since only reactive power is generated in the three-phase reactor 12, energy consumption due to the power generation action of the motor is extremely small, and the attenuation of the power generation action can be delayed.

This has the advantage that even if the power generation effect of the electric motor 3 is not so large, it can be detected reliably. 3 phase reactor 12
The current flowing through is detected by current transformers 6R and 6T, and further 3
The voltage generated across the voltage dividing resistor 9 is rectified by the phase full-wave rectifier circuit r, and is led to the operation monitoring device 15 and detected by the detection device 17.

If the cable from the motor 3 to the shearing device 2 is normal, the voltage across the resistor 9 will be a three-phase full-wave rectified waveform as shown in Figure 2a. If there is an abnormality such as a disconnection, the single-phase full-wave rectified waveform is used to detect the open phase of the load and the disconnection of the cable, as shown in FIG. 2b. By detecting the waveform by the detection device 17, it can be confirmed whether the current is flowing normally through the shearing device 2 and from the load side. The rotation speed of the electric motor 3 can be determined from the frequency of the waveform. With the above, it is possible to detect abnormal conditions such as the rotation speed being outside the allowable range, a phase loss on the load side, and a cable break. Next, turn off the shear breaker of the shear breaker and confirm that the voltage across the resistor 9 becomes zero as the current stops flowing, and the shear breaker function of the shear breaker 2 is normal. You can check that it is. Next, the second switch 13 is turned off. 0FF from operation monitoring device 15
Upon receiving the signal, the control circuit 5 automatically turns on the 0FF1 of the first switch 14, turns off the second switch 13, turns off the breaker, and turns off the second switch 13 using the timer in the control circuit 5. to be done. If the electric motor, shearing device, cable, etc. are normal, the judgment circuit 16 in the operation monitoring device 15 sends 0 to the control circuit 5.
Give N signal. The control circuit 5 stops the tripping function of the circuit breaker for about 50 msec and detects a restart current to prevent the circuit breaker from mis-tripping. Taking advantage of the fact that the probability of a failure occurring during the approximately 50 msec period immediately after confirming normality is close to zero, the trip function is stopped for an instant immediately after inspection to prevent mistrips. This is also one of the features of the present invention. Another method is to use transistor 4R in the case of transistor breaker.
, 4S, and 4T, a similar effect can be obtained by applying a soft start that gradually increases the base current. Further, when the 0FF signal is supplied from the operation monitoring device 15 to the control circuit 5, the first switch and disconnector are turned off, and then the second switch is turned off,
The same operation can be performed by subsequently turning on the breaker again and turning on the second switch B. If the monitoring of the operating status of the motor 3, the inspection of the shear disconnection device 2, the detection of open phases of the power supply 1 and the load 3, and the cable breakage inspection are performed sequentially for the motors connected in parallel, it is possible to operate multiple motors. Ensures consistent speed operation. As described above, according to the present invention, the current of the main circuit is detected, the secondary output of the current transformer is detected, and when the secondary output is normal in the 0N state of the shear breaker, the shear breaker is Check the continuity status of
The first switch of the main circuit is momentarily turned off, the second switch is turned on, current is passed through the reactor, detected by a current transformer, the frequency of the induced voltage of the motor is detected, and the rotation speed and load are determined. Monitor for open phase and disconnection of the cable from the load to the breaker, and then turn off the breaker and check whether the secondary output of the current transformer becomes zero. Check the shear breaker function and stop the trip function of the shear breaker for a short period at the time of restart to prevent the breaker from tripping due to the startup flow, then re-energize and continue operation. .

Since this is repeated at regular intervals, monitoring of the operating status of the motor, inspection of the cut-off device, phase loss of the power supply and load, and inspection of cable breakage can be performed in the same or a single operation in conjunction with each other. A driving monitoring device can be obtained.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing an embodiment of the present invention, Fig. 2 A, b
is a waveform diagram showing the output of a three-phase full-wave rectifier connected to the secondary current transformer in the present invention. 1...Power supply, 2...Shrinking device, 3.
...Electric motor, 4R, 4S, 4T... Transistor, 5... Control circuit, 6R, 6T...
...Current transformer, r... Rectifier circuit, 8,9...
...Resistor, 10...Diode, 11...
... Capacitor, 12 ... Three-phase reactor, 13 ... Second switch, 14 ... First switch, 15 ... Operation monitoring device, 16...
. . . Judgment circuit, 17 . . . Detection device.

Claims (1)

[Scope of Claims] 1. In an operation monitoring device for a motor connected to a three-phase power source via a shield breaker, a first opening/closing device connected in series between the three-phase power source and the shield breaker; a second switch that short-circuits each phase to which the first switch and the shield breaker are connected via a reactor; and a current transformer that detects the current flowing through the shield breaker. a rectifier connected to the secondary side of the current transformer, and a monitoring device for detecting the output of the rectifier, which opens the first switch and opens the second switch during operation of the motor. An operation monitoring device for a motor, characterized in that an abnormality in the motor circuit, such as a disconnection or an open phase, is detected from the output waveform of the rectifier by closing the switch. 2. In the item described in claim 1, if there is an abnormality in the motor circuit when the first switch is opened and the second switch is closed and inspected, the first switch and the circuit are disconnected. An operation monitoring device for an electric motor, characterized in that the device is kept open, and if normal, the tripping function of the cutter or disconnector is stopped for a short time or slowly started to restart the operation.