CN101464496A - Overload reliability test assembly for plastic case breakers and implementing method thereof - Google Patents

Abstract

The invention relates to a reliability test device in the field of low-voltage electrical appliances, in particular to a molded case circuit breaker overload reliability test device and a realization method. It is composed of a computer control cabinet and a test cabinet; among them, the computer control cabinet includes an industrial computer, a test voltage and current detection circuit, a control circuit and a test sample state detection circuit; the test cabinet includes a large current adjustment circuit, a current gear adjustment circuit, and a balance circuit switching circuit; the industrial computer is respectively connected with the test voltage and current detection circuit, the control circuit and the test sample state detection circuit; the test voltage and current detection circuit is respectively connected with the current gear adjustment circuit and the large current adjustment circuit; the control circuit is respectively connected with the current gear The position adjustment circuit, the large current adjustment circuit and the balance loop switching circuit are connected. This device can complete the overload reliability test of the entire molded case circuit breaker, realize automatic recording of test data and fault data, and can automatically shield faulty test samples without affecting the tests of other test samples. The test device can also Output and print test data. The device is controlled by a computer, easy to operate, and highly automated. It is widely used in the overload reliability test of molded case circuit breakers and has important social benefits and application value.

Description

Molded case circuit breaker overload reliability test device and implementation method

technical field

The invention relates to a reliability test device in the field of low-voltage electrical appliances, in particular to a molded case circuit breaker overload reliability test device and a realization method. The device can realize the automatic adjustment and steady flow of the test current, and can also automatically complete the overload reliability test of the entire molded case circuit breaker, realize the automatic recording of test data and fault data, and can realize automatic shielding of fault test samples, Without affecting the test of other test samples.

Background technique

Molded case circuit breaker (hereinafter referred to as molded case circuit breaker) is an important equipment in low-voltage electrical appliances, which is used to protect the safety of electrical circuits and equipment in low-voltage power distribution circuits, motors or other electrical equipment. When the electrical circuit or electrical equipment is overloaded or short-circuited, its release can act in time to reliably cut off the circuit; when the electrical circuit or electrical equipment is in a normal state, its main contact can be reliably connected circuit, its release should not malfunction.

With the increasing demand for molded case circuit breakers in the national economy, the requirements for the performance and quality of molded case circuit breakers are getting higher and higher. The reliability of the equipment is not high, especially the overload protection performance does not meet the needs of production and life, which will have a great impact on users and even cause serious economic losses.

The overload characteristic of the molded case circuit breaker means that the tripping characteristics of the low-voltage circuit breaker should meet the following requirements: when the test current is equal to 1.05 times the rated current, the release should not operate within the specified time; when the test current is equal to 1.3 times the rated current , The release should act within the specified time. When the test current is equal to 3.0 times the rated current, the release should not operate within the specified short time, and when the test current is equal to 0.9 times the rated current, the release should not operate within the specified time.

At present, in terms of related technologies involved in this test device, research at home and abroad mainly includes the following aspects: 1) In the late 1980s, the electrical contact wear test station of Engelhowd Company in the United States tested various types of contacts according to the requirements of IEC158-1. The contactor is tested. The main circuit is connected and disconnected by the computer through the solid state relay to control the traditional switch. According to different timings, the corresponding switch is controlled to realize the electrical life test of various types of contactors. The overload characteristic cannot be carried out. Test; 2) The American Westinghouse Company and Development Center have developed a parameter measurement and data processing system. The system can detect parameters such as test voltage and current. There are 10 detection channels in total, the sampling interval is 77μs, and the test accuracy is 1%. It can be used for parameter detection, but cannot control the test process; 3) Domestically, circuit breakers are used in such treatises as "Electrical Test Technology and Test Method" edited by Professor Lu Jianguo and Li Zhigang, and "Machine Tool Electrical Inspection and Test Manual" edited by Professor Lu Jianguo and Zhang Naikuan. A general method for overload characteristic verification is discussed. 4) In the plastic shell type circuit breaker life test device, a test device is designed to realize the closing/opening operation of the circuit breaker by means of a pneumatic operating mechanism to drive the handle of the circuit breaker. This device realizes a "soft" operation, but there is no contact status monitoring function during the test. 5) In the instantaneous tripping test bench for the instantaneous tripping test of the plastic case circuit breaker, a peak current detection device is installed, and the instantaneous test current is measured by detecting the peak value of the test current, and at the same time, it solves the problem of the tripping of the tripper. The measurement problem of action time. 6) The test device used by the Shanghai Electric Appliance Research Institute for the reliability test of the plastic case circuit breaker can only test the reliability of the operating characteristics. The method of checking after the test is carried out.

In order to guarantee and improve the quality of low-voltage electrical appliances and ensure the overload reliability of molded case circuit breakers, an overload reliability test device for molded case circuit breakers using computer direct control and detection technology is urgently needed.

Contents of the invention

The purpose of the present invention is to provide a molded case circuit breaker overload reliability test device and implementation method, the device can realize the automatic adjustment of the test current, automatic flow stabilization, and can also automatically complete the overload reliability test of the entire molded case circuit breaker, realizing Automatic recording of test data and failure data, and automatic shielding of failure test samples without affecting the tests of other test samples. The test device can also output and print test data, and is a test device that can be automatically controlled and recorded.

The device for the overload reliability test of a molded case circuit breaker provided by the present invention includes hardware and software. The software part is composed of an operating parameter display and modification module, a file processing module, a debugging test module, and an overload characteristic cycle test module; the hardware part It consists of an industrial computer, a test voltage and current detection circuit, a control circuit, a test sample state detection circuit, a large current generation circuit, a current gear adjustment circuit, and a balance circuit switching circuit. The industrial computer is composed of a display, a computer host, and a keyboard. The computer is connected to the test voltage and current detection circuit, the control circuit, and the test sample state detection circuit through the bus interface. The control circuit, the test sample state detection circuit, the large current adjustment circuit, and the current gear The adjustment circuit and the balance circuit switching circuit are connected with the test sample.

The test voltage and current detection circuit includes a voltage transformer, a current transformer, a voltage amplifier, and an A/D converter; the transformer, the voltage amplifier, and the A/D converter are connected in sequence. The A/D converter is connected with the computer, the two test power sources are respectively connected with the two voltage transformers, and the loop current is connected with the current transformers.

The control circuit includes a solid-state relay, contactor J1-contactor J19; the connection method is: the computer is connected to the coils of the solid-state relay, contactor J1-contactor J19 in sequence.

Test sample state detection circuit (4) comprises electromagnetic relay, photoelectric isolator, DC power supply, and its connection mode is: the contact of test sample is connected with the coil of electromagnetic relay, DC power supply, and the contact of electromagnetic relay is connected with photoelectric isolator, The photoelectric isolator is then connected with the computer.

The high-current regulating circuit includes electric voltage regulator, high-current transformer, current transformer, and A/D converter. Connection, the output of the electric voltage regulator is connected to the primary side of the high-current transformer, the secondary side output of the high-current transformer is connected in series with the molded case circuit breaker test sample and the current transformer, and the current transformer is connected to the test voltage and current detection circuit .

The current gear adjustment circuit includes five adjustment gears, which are 1500/5, 500/5, 150/5, 50/5, and 15/5 in sequence. In order to meet the requirements of test accuracy, two current transformers with different transformation ratios are used for small current regulation and large current regulation, respectively 0-400A and 0-1500A. The corresponding current gear can be selected according to the requirements of the debugging test.

Contactor J1—the contactor of contactor J19 and the balance resistor form a balance loop switching circuit, and its connection method is: the contacts in contactor J1-J3 are respectively connected in series with the balance resistor, then connected in parallel with J4, and connected in parallel with the first test sample connection, the contacts in contactors J5-J7 are respectively connected in series with the balance resistors, then connected in parallel with J8, and connected in parallel with the second test sample, and the contacts in contactors J9-J11 are respectively connected in series with the balance resistors, connected in parallel with J12, and connected in parallel with the second test sample. It is connected in parallel with the third test sample, the first test sample is also connected with the high-current transformer in the high-current regulating circuit (5), the third test sample is also connected with the current gear regulating circuit (6), and then connected with the large-current regulating circuit (5) The high-current transformer in (5) is connected.

The implementation method of the MCCB overload reliability test device provided by the present invention includes the following steps:

1) Pass 1.05 times the rated current, and then monitor the contact of the test sample. The contact state of the molded case circuit breaker does not change within the set time, and the test sample is normal. When the contact state of the molded case circuit breaker If the change occurs within the set time, the test sample is faulty, and the faulty test sample can be shielded through the contactor J1-J12 on the balance circuit switching circuit;

2) Pass 1.3 times the rated current to the test sample, the contact state of the molded case circuit breaker changes within the set time, the test sample is normal, otherwise the test sample is faulty, and the faulty test sample is tested through the contactor J1-J12 Shielding; return the test sample to a cold state;

3) Pass 3.0 times the rated current, the contact state of the molded case circuit breaker does not change within the set time, the test sample is normal, otherwise the molded case circuit breaker is faulty, and the faulty test sample is tested through the contactor J1-J12 shielding;

4) Pass 0.9 times the rated current to the test sample, the contact state of the molded case circuit breaker does not change within the set time, the test sample is normal, otherwise the test sample is faulty, and the fault test is carried out through the contactor J1-J12 The sample is shielded;

Through the above test process, a test cycle is formed, and the molded case circuit breaker is tested repeatedly, and the number of test cycles and test failures are recorded.

Beneficial effect and advantage of the present invention compared with prior art:

(1) The overload reliability test device of the molded case circuit breaker of the present invention can automatically complete the reliability verification test of the molded case circuit breaker without manual intervention in the test, which shortens the entire test time.

(2) The MCCB overload reliability test device of the present invention has two sets of power supplies. After adopting dual power supplies, the conversion time and adjustment time between different test currents can be shortened, and the accuracy of test results can be improved. At the same time, a returnable characteristic test of 3.0 times the rated current can also be carried out.

(3) The overload reliability test device of the molded case circuit breaker of the present invention can set and modify test parameters, these test parameters include 1.05 times, 1.3 times, 3.0 times, 0.9 times rated current, fast equivalent test current and corresponding test current The next test time.

(4) test current among the present invention is by computer control, when the resistance of test sample loop changes and power supply voltage fluctuates, test current remains constant;

(5) The MCCB overload reliability test device of the present invention automatically records the overload test time. When the output state of the MCCB changes, the computer automatically records the test time, avoiding the manual recording of the test time. Inaccurate and other human factors are convenient for people to analyze the failure after the test and achieve the purpose of improving the reliability of the molded case circuit breaker;

(6) Complete data protection function, the data will not be lost after an accidental power failure, and the collected data will not be destroyed after the power is restored. The test data is permanently stored in the computer and can be easily transferred to an external storage device. It can also be stored in other View and print out the test data conveniently on the computer;

(7) M1-100 and M1-225 molded case circuit breakers can be tested, and the test samples are fixed by pneumatic clamps for convenient and reliable connection; and output current connectors are provided, which can be used for other types of products with a rated current of 400A and below experimenting.

(8) It can test a single test sample or test all test samples. During the test, the computer provides operation prompts, which can reduce misoperation and terminate the test at any time. Easy to operate, good man-machine interface.

Description of drawings

Fig. 1 is a structural schematic diagram of the present invention.

Fig. 2 is a schematic structural diagram of the large current regulating circuit of the present invention.

Fig. 3 is a schematic structural diagram of the control circuit of the present invention.

Fig. 4 is a schematic structural diagram of a test sample state detection circuit of the present invention.

Fig. 5 is a block diagram of the test running computer program of the present invention.

Fig. 6 is a circuit diagram of an embodiment of the present invention.

Detailed ways

Further describe the present invention below in conjunction with embodiment and accompanying drawing thereof, but it is not limited to the present invention.

As shown in Figure 1, the MCCB overload reliability test device of the present invention includes a computer control cabinet and a test cabinet, and the computer control cabinet includes an industrial computer 1, a test voltage and current detection circuit 2, a control circuit 3, and a test sample state detection circuit 4. The test cabinet includes a large current adjustment circuit 5, a current gear adjustment circuit 6, and a balance circuit switching circuit 7. The connection method is: the industrial computer is connected to the test voltage and current detection circuit 2, the control circuit 3, and the test sample state detection circuit respectively. 4 are connected, the control circuit 3 is connected with the large current adjustment circuit 5, the current gear adjustment circuit 6, and the balance circuit switching circuit 7, and the test voltage and current detection circuit 2 is connected with the large current adjustment circuit 5 and the current gear adjustment circuit 6.

As shown in Figure 2, it is the large current regulating circuit 5 of the present invention, the test current generating circuit includes an electric voltage regulator, a large current transformer, a current transformer, and a voltage transformer, and its connection mode is: the input of the electric voltage regulator is a power supply Voltage, and connected with the computer "up" and "down" control lines, the output of the electric voltage regulator is connected with the primary side input of the high-current transformer and the voltage transformer, and the secondary side output of the high-current transformer is connected with the molded case circuit breaker, current The transformers are connected in series, and the current transformers and voltage transformers are connected to the test voltage and current detection circuit 2. The computer compares the detected current value with the set current value. When the detected current value is higher than the set current value Hours, the computer controls the electric voltage regulator to increase the voltage. When the detected current value is greater than the set current value, the computer controls the electric voltage regulator to decrease the voltage until the detected current value is equal to the set current value. , When the power supply voltage fluctuates or the test sample circuit resistance changes, so that the test current is different from the set value, the computer will automatically adjust the voltage to make the test current equal to the set value, and realize the steady flow of the test current.

As shown in Figure 3, it is the control circuit 3 and the balance circuit switching circuit 4 of the present invention, the control circuit 3 includes a solid state relay, a contactor J1-contactor J19, and the contacts of the contactor J1-contactor J19 form a balance circuit with a balance resistor The switching circuit is connected in the following way: the computer is connected to the coil of the solid-state relay, contactor J1-contactor J19 in sequence, the contacts in the contactors J1-J3 are respectively connected in series with the balance resistor and then connected in parallel with J4, and connected with the first test sample Connect in parallel, the contacts in the contactors J5-J7 are respectively connected in series with the balance resistors and then connected in parallel with J8, and connected in parallel with the second test sample, the contacts in the contactors J9-J11 are respectively connected in series with the balance resistors and then connected in parallel with J12, And connected in parallel with the third test sample, the first test sample is also connected with the large current transformer in the large current regulating circuit (5), the third test sample is also connected with the current gear regulating circuit (6), and then connected with the large current regulating circuit (5). The high-current transformer in the circuit (5) is connected. In the figure, J1-J19 are 19 contactors. The computer controls the solid-state relay through the input and output ports of the bus interface, and the solid-state relay drives the contactor, thereby realizing the control of the computer on the contactor J1-J19. The first test sample is closed to perform the test. For the test, select the appropriate contactor to close in J1-J4, and replace the test sample with a balance circuit to form a test circuit after the test sample is moved or cut off. Similarly, the contactors J5-J8 control the test of the second test sample, and the contactors J9-J12 control the test of the third test sample.

As shown in Figure 4, it is the test sample state detection circuit of the present invention, the contact of the test sample is connected with the coil of the electromagnetic relay and the DC power supply, the contact of the electromagnetic relay is connected with the photoelectric isolator, and the photoelectric isolator is connected with the computer again. The contact of the test sample is closed, the electromagnetic relay is energized, the photoelectric isolator is turned on, the computer receives a low-level signal, the contact of the test sample is disconnected, the photoelectric isolator is not conducted, and the computer receives a high-level signal. The computer reads in the digital signal representing the state of the contact of the test sample to monitor the state of the contact of the molded case circuit breaker to determine whether the molded case circuit breaker operates.

The overload reliability test device of the molded case circuit breaker of the present invention completes the overload reliability test of the molded case circuit breaker under the control of the computer. The program block diagram is shown in Figure 5, and its test operation program is:

(1) Run the MCCB overload reliability test program after the computer is powered on;

(2) Judging whether there is a test menu item selection operation (mouse click or keyboard input), repeat step 2 when there is no test menu item selection operation, and turn to step 3 when there is a test menu item selection operation;

(3) Determine whether the function menu is set for the test parameters, if not go to step 4, if so, perform the following processing:

Parameters are set through the mouse and keyboard, and the industrial computer automatically saves the set operating parameters. Operating parameters include: rated current value of the test product, non-operating time at 1.05 times rated current, operating time at 1.3 times rated current, non-operating time at 3.0 times rated current, non-operating time at 0.9 times rated current, fast Test current, test sample type, allowable failure times, test times and other parameters. After setting the running parameters, save and display the running parameters, and then go to step 2.

(4) Determine whether it is a test file processing menu, if not, turn to step 5, if so, perform the following processing:

File processing includes data file storage, transfer, real-time display and printing of test data, etc. The test data can be saved automatically, and the previous test data can be read. At the same time, the test data can be displayed on the computer monitor or output and printed by the printer. After the data processing is completed, go to step 2.

(5) Determine whether it is the debug operation menu, if not go to step 6, if so, perform the following processing:

The commissioning operation includes functional modules such as test voltage and current detection, steady current test, test product separation and closing, power supply lifting and linear correction. Carry out the detection of power supply voltage and loop current, the regulation and stabilization of predetermined current, the control of opening and closing of the test product, the lifting test of auxiliary power supply and the linearity correction of the collected data. These modules complete the preparation and testing work before the formal test, and are used to detect the line connection, the installation of the test product, and the data acquisition accuracy and control accuracy of the board. After the debugging module is running, go to step 2.

(6) Determine whether it is the overload reliability cycle test operation menu, if not go to step 7, if so, perform the following processing:

The entire reliability test is controlled by the test operation module, which is responsible for controlling the test process of the test device and the recording of test data during the entire test process. This module can complete the stable test current, monitor the action time, and monitor the fault mode.

The function module controls the switching on and off of the large current regulating circuit 5, the current gear regulating circuit 6 and the balance circuit switching circuit 7 through the control circuit 3; the output voltage of the voltage regulator is detected by the voltage and current detection circuit 2 during operation And parameters such as the current in the test main circuit where the test product is located, process the collected parameter signals through the relevant judgment program in the host computer, and then accurately adjust and control the test main circuit current through the control circuit 3, and adjust to the test After reaching the specified current value, test the sample, determine the tripping condition of the sample and record the test results. When a test product fails, the faulty test product is shielded by the balance circuit switching circuit, and the test of other test products is continued. After the test run is complete, go to step 2.

(7) Judging whether it is a test and exiting the menu, if not, go to step 2, and if so, exit the overload reliability test of the molded case circuit breaker.

As shown in Fig. 6, the specific circuit of the overload reliability test of the molded case circuit breaker of the present invention is given.

In the test sample state detection circuit 4 in Fig. 6, the test sample moves, the electromagnetic relay is energized, the normally open contact of the relay is closed, the normally closed contact is disconnected, and the normally open and normally closed signals input to the computer are high level and low level respectively. flat. The computer reads in the digital signal representing the state of the contact of the test sample to monitor the state of the contact of the molded case circuit breaker to determine whether the molded case circuit breaker operates.

The current gear adjustment circuit 6 in FIG. 6 includes five adjustment gears, which are 1500/5, 500/5, 150/5, 50/5, and 15/5 in sequence. According to the size of the test current in the circuit during the test, the contacts J13-J17 of the AC contactor J13-J17 are used to control the selection of the corresponding current gear.

In Fig. 6, the control of the test sample by the computer is realized through the control circuit 3 and the balance circuit switching circuit 7. The output of the computer is connected to resistors R19-R37, resistors R19-R37 and solid-state relays SSR1-SSR19 to control 19 AC contactors J1 - AC contactor J19, the contacts J1-J12 of the AC contactor control the test of the first test sample, the second test sample, and the third test sample respectively, and the first test sample is closed to test it, and select it in J1-J4 The appropriate contactor is closed, the test sample is moved or cut off, and the balance circuit is used to replace the test sample to form a test circuit, so as to realize the test control of the first test sample by the computer. Similarly, the computer realizes the test of the second test sample through the contactor J5-J8 Control, the computer realizes the test control of the third test sample through the contactor J9-J12.

In the large current regulation circuit 5 in Figure 6, this design has two sets of power supplies, resistors R10, R11, R12, R13, photocouplers TLP521-1, TLP521-2, TLP521-3, TLP521-4 to form motors M1, M2 The lifting control circuit, the control terminal is controlled by the four output ports of the computer. Taking M1 as an example, when the two ports are both high or low, the motor M1 does not turn. When the first port is high , when the other port is at low level, the motor M1 rotates forward, driving the voltage regulator BY1 to boost the voltage, and the current in the test sample circuit increases. When the first port is at low level and the other port is at high level, the motor M1 Reverse, drive the voltage regulator BY1 to step down, and the current in the test sample circuit decreases. The output of the voltage regulator BY1 is connected to the high-current transformer BL1, and the output of the high-current transformer BL1 is connected to the current gear adjustment circuit 6, and forms a current loop with the contactor contacts and the test samples in the balance loop switching circuit 7. The computer realizes the regulation and control of the test current through the large current regulation circuit 5 .

In the voltage and current detection circuit 2 in Fig. 6, the secondary side connection resistor R16 of the current transformer in the current gear adjustment circuit 6 is converted into a voltage, and the voltage is amplified by the amplifier circuit composed of the resistors R17, R18 and the operational amplifier U1, and Input to the A/D converter, the A/D converter converts the analog voltage into a digital signal and then inputs it to the computer. The output terminals of the voltage regulator BY1 and BY2 enter the input terminal of the voltage transformer through the resistor to collect the voltage. The voltage is amplified by the amplifier circuit composed of the resistor and the operational amplifier, and input to the A/D converter. The A/D converter will The analog voltage is converted into a digital signal and input to the computer.

Application example, when taking a molded case circuit breaker with a rated current of 100A as an example to conduct an overload reliability test, the test method is as follows:

First pass a test current of 105A to the test product, and then monitor the contact of the test product. If the contact state of the molded case circuit breaker does not change within 7200s, the test product is normal, otherwise the test product is faulty. Then pass the test current of 130A, the contact state of the molded case circuit breaker changes within 7200s, the test product is normal, otherwise the test product is faulty.

The specific operation process is as follows:

First, the power supply is automatically selected according to the test current. The test current of 105A is adjusted by power supply 1, and the test current of 130A is adjusted by power supply 2. First carry out the balance circuit test of the 130A test current to determine the required balance circuit and current transformer circuit. Call the current regulation function to adjust the 130A current. Use the same method to adjust the 105A current and determine the balance circuit.

The method of current regulation is as follows: determine the percentage current to be adjusted according to the relationship between the set current and the rated current, if unsuccessful, change the current regulation percentage; if successful, stabilize for 3 seconds. Disconnect the power supply and measure the current voltage. The current voltage divided by the current regulation percentage is the adjustable voltage value. Adjust the voltage value to obtain the set test current value. For example, first determine that the current regulation percentage is 20%, turn on the power supply, adjust the current of 0.20*105A, detect the voltage value U ₁ output by the voltage regulator at this time, and turn off the power supply. Then control the voltage regulator to increase the voltage to U ₂ /0.2, and the current in the circuit is 105A at this time. The adjustment method of test current 130A is also similar.

Stability of the test current: There is a certain deviation between the current adjusted according to the above method and the actual test current, so it is necessary to stabilize the current. Detect the current in the circuit in real time and compare it with the required test current value, control the voltage regulator to step up and down, and control the deviation between the two within the allowable range of error, that is, the stabilization process of the test current.

Start the test: first conduct the 105A current test. Use the control circuit and the electric operating mechanism to control the closing of the test product, and close the power supply 1. During the test, it is necessary to check the movement of the test object, and the test object that has moved will not be detected, and it will be recorded as "early action"; if all the test objects move, stop the test in this test process. When the test time is up, if the test product does not move, record it as "normal", then turn on the 0.9I _e power supply, judge the failure of the test product, and record the failed test product. If the number of failures of all test items has been reached, exit the test, otherwise continue the test. Close the power supply 2, and carry out the 130A current test. During the test, it is necessary to check the movement of the test object, and the test object that has moved will not be detected, and it will be recorded as "normal"; if all the test objects are in motion, the test in this test process will be stopped. When the test time is up, if the test object does not move, it will extend the test time. The extended time is 7200s*0.1 to detect the movement of the test object during the extended test time. If the test object moves, it will be recorded as "slow motion", otherwise Recorded as "Reject Action". Turn on the power supply 2, judge the failure of the test product, and record the failure of the test product. If the number of failures of all test items has been reached, exit the test, otherwise continue the test.

At this point, a process test is completed, and the next process or next cycle test can be carried out.

Claims (8)

1. A molded case circuit breaker overload reliability test device, which is composed of a computer control cabinet and a test cabinet, characterized in that: the computer control cabinet includes an industrial computer (1), a test voltage and current detection circuit (2), and a control circuit (3), the test sample state detection circuit (4); the test cabinet includes a large current regulation circuit (5), a current gear regulation circuit (6), and a balance circuit switching circuit (7), and its connection mode is: the industrial computer is connected with the The test voltage is connected to the current detection circuit (2) and the control circuit (3), and the control circuit (3) is connected to the large current adjustment circuit (5), the current gear adjustment circuit (6), and the balance circuit switching circuit (7). The voltage and current detection circuit (2) is connected with the large current regulation circuit (5) and the current gear regulation circuit (6). 2. Molded case circuit breaker overload reliability test device according to claim 1, characterized in that: said test voltage and current detection circuit (2) includes a voltage transformer, a current transformer, a voltage amplifier and an A/D Converter, its connection method is: transformer, voltage amplifier and A/D converter are connected in sequence, A/D converter is connected with computer, two test power supplies are connected with two voltage transformers respectively, loop current and current transformer connect. 3. Molded case circuit breaker overload reliability test device according to claim 1, characterized in that: said control circuit (3) includes a solid state relay, contactor J1-contactor J19, and its connection mode is: computer and The coils of solid state relay, contactor J1-contactor J19 are connected sequentially, the contacts in contactors J1-J3 are respectively connected in series with the balance resistor and then connected in parallel with J4, and connected in parallel with the first test sample, the contacts in contactors J5-J7 The contacts are respectively connected in series with the balance resistor and then connected in parallel with J8, and connected in parallel with the second test sample. One test sample is also connected to the high-current transformer in the high-current adjustment circuit (5), and the third test sample is also connected to the current gear adjustment circuit (6), and then connected to the high-current transformer in the high-current adjustment circuit (5). . 4. The overload reliability test device for molded case circuit breakers according to claim 1, characterized in that: the test sample state detection circuit (4) includes the detection of the main contacts and auxiliary contacts of the test samples; The contact is connected with the coil of the electromagnetic relay and the DC power supply, the contact of the electromagnetic relay is connected with the photoelectric isolator, and the photoelectric isolator is connected with the computer. 5. Molded case circuit breaker overload reliability test device according to claim 1, characterized in that: said high current regulating circuit (5) includes electric voltage regulator, high current transformer, current transformer, A/D The connection method of the converter is as follows: the input of the electric voltage regulator is the power supply voltage, and it is connected to the "up" and "down" control lines of the computer, the output of the electric voltage regulator is connected to the primary side of the high-current transformer, and the high-current transformer The secondary side output is connected in series with the molded case circuit breaker test sample and the current transformer, and the current transformer is connected with the test voltage and current detection circuit (2). 6. The overload reliability test device for molded case circuit breakers according to claim 1, characterized in that: the current gear adjustment circuit (6) includes five adjustment gears, which are 1500/5, 500/5 , 150/5, 50/5 and 15/5, according to the debugging test requirements, select the corresponding current gear. 7. The overload reliability test device for molded case circuit breakers according to claim 1, characterized in that: said balance circuit switching circuit (7) includes 3 resistance balance circuits and 1 short circuit balance circuit. 8. A method for realizing an overload reliability test device for a molded case circuit breaker, characterized in that it includes the steps of: 1) Pass 1.05 times the rated current, and then monitor the contact of the test sample. The contact state of the molded case circuit breaker does not change within the set time, and the test sample is normal. When the contact state of the molded case circuit breaker If it changes within the set time, the test sample is faulty, and the faulty test sample can be shielded through the contactor J1-J12 on the balance circuit switching circuit; 2) Pass 1.3 times the rated current to the test sample, the contact state of the molded case circuit breaker changes within the set time, the test sample is normal, otherwise the test sample is faulty, and the faulty test sample is tested through the contactor J1-J12 Shielding; return the test sample to a cold state; 3) Pass 3.0 times the rated current, the contact state of the molded case circuit breaker does not change within the set time, the test sample is normal, otherwise the molded case circuit breaker is faulty, and the faulty test sample is tested through the contactor J1-J12 shielding; 4) Pass 0.9 times the rated current to the test sample, the contact state of the molded case circuit breaker does not change within the set time, the test sample is normal, otherwise the test sample is faulty, and the fault test is carried out through the contactor J1-J12 The sample is shielded; The above steps 1), 2) or steps 1), 2), 3), and 4) constitute a test cycle, and the molded case circuit breaker is tested repeatedly, and the number of test cycles and test failures are recorded.

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