| With the enhancement of automatic in mining coal working station and development of the microcomputer control technology, control pattern over the mining device change from single switch to combined switch. The combined switches, namely the load control center, consist of many vacuum contact device and their drivers,which is a kind of anti exploding electric appliance equipment which is reliable and controlled intellectually.The main equipment it can control includes coal mining machine, squeegee convey machine, transport machine, adhesive tape transport,driving machine, hydraulic pressure pump and so on. It can control singe speed motor in sequence and double speed motor switch.Besides, it has over current protection, short-circuit function, leakage current closedown, protection, phrase-failure protection and phrase-imbalance protection.Control function and protection function is realized by microcomputer. Although there are a lot of computer control methods, considering complexity of working conditions in the mine, PLC which has a high anti jamming ability is selected as main computer protection components. With the enhancement of mining device power, energy supply system of mining working station in our country has rised from 1.14kV to 3.3kV, the 1.14kV combined switch already could not meet demands, the domestic 3.3kV combined switch has already been developed, but its intelligence was not very high, the combined switch abroad is advanced, but the price is too expensive, and it is difficult to maintain.At the same time, there is a trend that the massive 1.14kV combined switch will be replaced by 3.3kV, the prospect very is broad. Because of this, a lot of study on combined switch has been carried out in this article.Compared with 1.14kV combined switch, phrase-failure closedown,avoiding button misoperation and phrase-imbalance are added in the 3.3kV one.Meanwhile, some new methods on protection and control are developed.The study includes creepage detect circuit,phrase-failur detect circuit, material safety circuit of avoiding button misoperation, overcurrent protection,short-circuit protection, phrase-imbalance protection, phrase-failure protection, multi-loop combine control and HMI design.Creepage detect and phrase-failure detect are carried out in every output loop before main disconnector is on.if any faults occur, forbid the output loop on. If faults occur suddenly when working, protection function is activated in the loop.naming it has creepage closedown and phrase closedown.the circuit between remote buttons and PLC inputs in the combined switch will be a material safety circuit of avoiding button misoperation, which is realized in the hardware design.Every fault protection and control belong to software design. In the overcurrent protection, a formula considering its energy accumulation according to time is developed to ptotect loop in the form of inverse time limit. Reliability of the formula is validated in the chapter 5.Eignt to ten overload multiple is considered as short-circuit according to narional standards of coal industrial,and should be protected.phrase-imbalance protection has its judgement basis in the form of phrase-imbalance ratio.control function includes control on the 2-6 loop combine and switch on the double speed motor.HMI is to monitor every output loop status and operation of combined switch, by using industrial touching screen. its' function includes display,paraments set and fault query.Touching screen is placed inside combined the switch near the door when designing its structure because of it's special circumstance in the mine to make it easy to operation through special window and control buttons for operator.Besides, the study plays more emphasis on the anti-jamming, developing some ptactical hardware and software the anti-jamming measures. |
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