[Small circuit breaker reliability detection device]:1 Introduction Small circuit breaker belongs to protective electrical appliances, which is used to protect the safety of electrical circuits and equipment. When the electrical circuit or electrical equipment occurs load, short circuit and other faults, its tripper should be able to act in time, reliably cut off the circuit; when the electrical circuit or electrical equipment is in normal state, its main contact should be reliable.
1 Introduction
Small circuit breakers belong to protective electrical appliances, which are used to protect the safety of electrical circuits and equipment. When the load and short circuit failures occur in the electrical circuit or electrical equipment, its tripper should be able to operate in time and cut off the circuit reliably; when the electrical circuit or electrical equipment is in normal state, its main contact should be able to connect the circuit reliably, and its tripper should not act incorrectly. Therefore, it is necessary to carry out operation reliability test and instantaneous reliability test for small circuit breakers. In order to study the reliability of small circuit breakers, besides the reliability index and test scheme, the most important thing is to develop a set of reliability test equipment to implement its reliability standard. Only in this way can the reliability research of miniature circuit breakers be put into practice, and can provide an effective means for manufacturers of miniature circuit breakers to improve product reliability and enhance product competitiveness.
In this paper, according to the reliability testing standards of miniature circuit breakers and the specific requirements of users, the operation reliability and instantaneous reliability of miniature circuit breakers are tested by self-designed test equipment, and the final test data are obtained to identify the advantages and disadvantages of this type of miniature circuit breakers.
2. Hardware Design of Reliability Testing Device
The hardware of reliability test equipment for small circuit breaker mainly consists of test control cabinet, test cabinet, high current cabinet and load circuit board.
The control cabinet is composed of industrial computer, printer and PCL-720 control card and PCL-818 series acquisition card produced by Yanhua Company.
The test cabinet is mainly composed of eight mechanical handles driven by motors. The industrial control computer controls the mechanical handle driven by the motor and collects the voltage at both ends of the contact to determine whether the contact is invalid or not. The specific process is shown in Figure
The industrial computer controls the turn-on and turn-off of the positive and reverse circuit of the motor through the digital output port of the PCL-720 control card, so that the positive or reverse turn of the motor drives the opening and closing of the test sample. The mechanical structure controlled by the motor is equipped with Hall elements. When the motor rotates in place, Hall elements will output the in-place signal. Through the digital input port of the PCL-720 control card, the motor is in place and the digital output port of the PCL-720 control card can disconnect the forward or reverse circuit of the motor and stop the motor from turning. In the process of motor forward or reverse, the closed and open voltages at both ends of contacts can be collected by data acquisition card to detect whether the voltage value meets the requirement or not, and if it does not meet the requirement, the contact failure data can be recorded.
Figure 2 is the circuit model of data acquisition. When the contacts to be measured are closed, the contact voltage is 0V, and the voltage collected by the acquisition card should be about 0V. When the contacts to be tested are opened, the contact voltage is 24V, and the maximum range of analog acquisition by PCL-818HG acquisition card is 10V. Before measurement by the acquisition card, the voltage is divided by R1 and R2 before measurement. So, the measured voltage value is
Large current cabinet is mainly composed of main circuit contactor, voltage regulator and transformer. Its function is to simulate a large fault current. For type C miniature circuit breaker, the instantaneous reliability test current is 5 times and 10 times rated current. When 5 times rated current is passed, the small circuit breaker tripper should not operate; when 10 times rated current is passed, the small circuit breaker tripper should operate in time and cut off the circuit reliably. During the transient reliability test, the current value can reach 5 or 10 times by adjusting the voltage regulator. Then, close the test circuit to be tested, collect the voltage at both ends of the contact through PCL-818HG acquisition card, and compare the collected voltage value with the allowable value to judge whether the test is invalid.
Load circuit boards mainly provide resistive loads for test contacts under the conditions of 24V and 0.1A. Fig. 2 shows the schematic diagram of the load circuit and sampling circuit provided by the load circuit board. When the external power supply is 24V, the load resistance is 0.24k to provide 0.1A load current for circuit breaker contacts.
3. Software Design of Reliability Testing Device
Software is an important part of realizing operation reliability test and instantaneous reliability test of miniature circuit breaker with hardware. The control interface is compiled by nesting method of VC++/MFC and assembly language. Because of the incomplete protection of Windows 98, it is necessary to use this programming method in Windows 98 environment.
The interface of the reliability test device for small circuit breakers is shown in Fig. 3. By clicking on the corresponding menu items, various tests of small circuit breakers can be realized.
In this interface, clicking on the corresponding menu will bring up a dialog box or a drop-down menu. The main functions of the application interface are test initialization, test parameter setting, test assistant operation, operation reliability test, instantaneous reliability test, data viewing and help.
The operation flow chart of the application interface is shown in Fig. 4. After entering the application interface, the test parameters are set up and the test initialization is carried out. If the test is not detected in the initialization, the system gives a hint that the reliability test cannot be carried out. If the test device detects the test item, it can click on the start button for operational reliability or the start button for instantaneous reliability.
