Design and application of the general-purpose circuit breaker chess piece Beijing Institute of Petrochemical Technology (102600) Lu Zhuwei Xin Peng Yuexiang Zhou Xiaozheng Ma Jinglan Zhang Xiaoyan 0 Overview Low-voltage electrical appliances are widely used in China, but also have many specifications, but the existing low-voltage electrical appliances are almost all They are all traditional and non-intelligent. Compared with foreign countries, there is not only a big gap, but also high energy consumption, large error, low performance and poor reliability. With the substantial increase in the price-performance ratio of single-chip microcomputers, it has become urgent to apply computer and microprocessor technology to industrial control on a large scale, especially to increase the development of intelligent functions of low-voltage electrical appliances. According to China's national conditions, the author developed a general-purpose intelligent module, which has the functions of simple setup, reliable use, energy-saving control, online change settings and display. When the module receives the closing or breaking command, it can control the three contacts according to the optimal breaking and closing phase angle to perform zero-crossing and closing, thereby reducing the energy of the spark and prolonging the service life of the contact. Because the module is independently designed and installed independently, it has strong relative independence and anti-interference. Combining it with contactors and circuit breakers can easily improve their performance and form a circuit breaker and contact with intelligent functions. , motor controller and protector. On the basis of this, the two-way communication function with the central control computer is added, and a local control network and a simple DCS system are formed, which greatly improves the performance index of the low-voltage electrical appliance. 1 Basic functions and working principle of intelligent modules At present, contactors, circuit breakers and protectors (such as thermal relays) used in China are mostly mechanical and non-intelligent, generally for AC suction, AC holding and random breaking, and wire package. The voltage has 220V and 380V. It can be seen from the block diagram that after the power is turned on, the rectifier circuit, the regulated power supply loop and the single-chip microcomputer system are powered. After the phase current setting is completed, the microcontroller starts sampling and compares with the set value. The start loop and the freewheeling loop system are in standby state; while the MCU continuously samples, compares, and records the power supply voltage and phase, if the start signal is obtained, it will pass the start loop to the line pack in a timely manner in no more than 20ms. Coupled with a corresponding high voltage, the moving contact overcomes the spring thrust and inertia under the action of strong excitation, and quickly moves to the static contact; at the same time, the single-chip control the freewheeling circuit to provide a suitable holding voltage in time to make the line The package works under very low voltage and current, which is safe, reliable, power-saving and energy-saving; once the power supply voltage is less than the release voltage, The MCU immediately stops supplying power to the line pack through the freewheeling circuit under suitable phase conditions, and the contacts are reset by the action of the spring. After the phase current is set, the phase current will increase sharply once the startup process occurs, and the degree of current surge and the duration of the surge increase are related to the load carried by the motor. Therefore, when the author compiles the software, according to the ministerial standards and industry design and application requirements, this part of the program is added, that is, the single-chip microcomputer can distinguish the different load conditions or even the stalling and short-circuit, and automatically select the corresponding startup time. Thereby the motor can be started with load. When the intelligent module and the circuit breaker are connected, a smart release is formed, and the single chip also samples the leakage, voltage, current and phase, and the output trip signal makes the circuit breaker operate in time. 2 The hardware design of the intelligent module is designed to be easy to install and use. The author designs the input voltage of the module into an adaptive type. After the single chip is sampled and compared by the sensor, the final output is a level signal or a pulse width signal of a certain frequency. Used to drive the actuator. Because of the strong electromagnetic interference, it often causes malfunction. For this reason, the author has taken a number of measures to overcome, such as shielding, filtering, constant magnetic protection and photoelectric transmission. The MCU series of American Motorola and the PIC series of Microchip are used respectively. The former has strong anti-jamming performance, and the latter has a good price-performance ratio. With practical anti-interference measures, it can also achieve good results. Because these MCUs have rich internal resources, they are displayed in time-sharing dynamic scanning mode. The external components are very few, which not only reduces the cost, but also greatly improves the reliability. 3 Intelligent module software block diagram The level of intelligence and reliability of the module depends mainly on the selection of the control scheme and the preparation of the software. The overall block diagram of the program is as shown. When the program is executed, the grid voltage is first sampled. If the grid voltage imbalance is greater than 30%, the program refuses to continue execution and displays the item with an LED; after this test is passed, the MCU is based on the phase synchronization signal and the last time. Pulling and breaking the record of the zero-crossing contact, selecting the next contact as the target contact, and selecting the appropriate phase and phase of the suction phase according to the value of the sampling voltage, entering the control standby state, once the suction command is When the MCU immediately executes the suction subroutine, the end of the suction is completed, and the MCU turns off the main controller. The system automatically enters the holding phase, and the line package maintains the excitation state with low voltage and small current. 4 Experimental results The author combined the intelligent module with the trip device of the contactor and circuit breaker, and carried out a large number of experiments. The basic situation is as follows. The operating voltage of the contactor winding is 380V. In the case of 220V AC, the result is that the contactor cannot be attracted. When combined with the intelligent module, it is also completed in the case of 220V. Observed with an oscilloscope, the time error of the pull-in command and the actuator is no more than 40ms, and 76% or more is within 20ms. Under the premise of not generating one or two bounces, the pull-in current is 0.12A, and the holding current is only 6mA, the effect is quite satisfactory. When the external voltage drops to 160V, the contact is automatically disconnected, and the MCU is in the sample and standby state. The breaking process has similar conclusions, but two settings are made for the microcontroller: replacing the sampling contacts and determining the breaking moment. The new sensing technology and process sampling technology will improve the closed-loop control of zero-crossing and improve the intelligence of the module. After the start-up process, the line package operates at low voltage and low current. While maintaining this state, the MCU monitors the pull-in voltage and the unbalance of the power grid. Once a short circuit, phase failure, grid voltage imbalance exceeds 30%, the grid voltage is lower than 160V, and the starting current exceeds the set value. The control circuit immediately enters the disconnection subroutine to perform power loss and disconnection according to the zero-crossing requirement, thereby protecting the safety of the equipment. The serial port of the MCU is connected with the RS-232 of the microcomputer, and the current set values ​​of the MCU are read back to the microcomputer display, so that the combination of the operating state of each controlled object can be monitored in real time and is easy to operate. 5 Conclusion For different occasions, choose different MCUs and combine them to form a product with strong anti-interference ability and operational reliability. Combined with new sensing technology, it can increase the temperature including monitoring contact. The intelligent products with learning function, combined with a large number of contactors and circuit breakers in China, will make China's low-voltage electrical appliances get rid of the backward situation and improve the grade of low-voltage electrical appliances in China. (Finish) Magnetic Board,Glass Whiteboard,Office Whiteboard,Flexible Magnetic Whiteboard Dongguan Aoxing Audio Visual Equipment CO.,Ltd , https://www.aoxing-whiteboard.com
Design and application of universal circuit breaker module