In the picture number: TM86: B pressure V5 is proportional, /> can always be n times the relationship with the grid frequency. If W is to ensure the reliable operation of the main circuit, the circuit is required to follow, the frequency of the power grid rises, that is, the V2 cycle decreases / A is output by the phase detector 1 Foreword GP-Cb type high frequency induction heating equipment was purchased by our factory in the early 1960s Into. As we all know, the high-pressure rectifier system of this equipment uses mercury-filled thyratrons. The thyratrons have strict requirements on the working environment, and are prone to the disadvantages of reverse arc, high failure rate, low work efficiency and high maintenance costs. With the rapid development of electronic technology, the advent of new electrical products has provided a prerequisite for the transformation of high-frequency equipment.
2 The thyratron of high voltage rectification system not only has the above shortcomings, but also needs a long time to warm up every time it is turned on, it consumes a lot of electricity, and it is easy to produce a lot of harmonics, which seriously pollutes the power grid. Decided to transform the high-voltage rectification system of high-frequency equipment.
Replacing the old thyristor rectifier system with a high-voltage silicon rectifier bridge. When selecting a high-voltage silicon rectifier bridge, there are two main electrical specifications, namely the voltage resistance and current resistance of the silicon rectifier bridge. According to the use conditions of the equipment, the nominal value of the withstand voltage and current resistance must have a certain margin to prevent the surge voltage of the inductive device from damaging the device when the switch is turned on and off under no-load conditions.
The nominal value of the withstand voltage is generally 1.2 to 1.5 times the maximum voltage of the actual application, and the nominal value of the current resistance is generally more than 2 times the maximum current of the actual application.
The thyristor voltage regulator power supply now uses a thyristor high-voltage rectification system, and then it will face the choice of thyristor voltage regulator power supply. Because the application of high-frequency induction heating equipment when the fundamental wave and high-order harmonic diffusion is relatively serious, in There is a high-frequency strong electric field in a large area of ​​the workshop. This strong electric field around the high-frequency equipment interferes with the trigger signal of the thyristor very seriously. The voltage regulator of the thyristor should have strong anti-interference. Capability, and the microcomputer-controlled AC voltage regulator has the characteristics in this respect. Therefore, when transforming the equipment, we adopted the KKTY-3 type microcomputer-controlled AC voltage regulator.
This voltage regulating power supply is mainly composed of a main voltage regulating circuit and a control circuit. The main circuit is composed of three pairs of anti-parallel high-power thyristor components. The core part of the control circuit is the MCS-48 series 8-bit single-chip microcomputer. In addition, there is a synchronization circuit, pulse formation and amplification, the circuit given signal, DC Negative voltage feedback and overcurrent protection circuit.
The voltage waveform shaping circuit (see) turns the 24V synchronous, AC voltage signal R into a square wave V2, the phase detector is 90 * phase detection, which is actually an XOR gate circuit, that is V4 = V2 ten Vb, Vb is divided by After the frequency circuit is obtained, the square wave voltage is the same as the system frequency. After the phase discrimination, the square wave voltage of 100 Hz is obtained. Its high level and width are related to the V2 and VB phases. V4 becomes a flat DC voltage after low-pass filtering. (Contains a certain ripple) V5, V5 is the control voltage of the voltage-controlled oscillator, the output of the voltage-controlled oscillator / 0 is a series of high-frequency pulses, the frequency and control of the electric flexible belt conveyor are super The development and application of the mine Liu Yongsheng, Wu Ziduan, Wang Yanlin, Fan Qinglin (Zheng Coal Group Co., Ltd. Chaohua Coal Mine, Xinmi 452385, Henan Province) are widely used, and have made some discussions on the large-angle turning belt conveyor.
In the picture number: TD528: A Foreword Under normal circumstances, the belt conveyor must be laid straight, otherwise it will run away. However, in the design process of specific wells and tunnels, in order to improve the coal recovery rate or to bypass the goaf and protect the coal pillars, some conveyor lanes turn at different angles in the horizontal direction. If laying an ordinary belt conveyor cannot run at all, multiple machines must be connected in series. However, with the development of mines, especially the construction of high-yield and efficient mines in recent years, it has become an inevitable trend to simplify transportation and realize the long-distance transportation of a belt conveyor. The role of flexible belt conveyors in underground transportation systems has been paid more and more attention.
Chaohua Mine has a total length of 280m under the auxiliary roadway at the 12011 working face mined in April 1995. In order to bypass the mined-out area of ​​12031, the lower auxiliary roadway has two turns of 6 * and 7 * in the horizontal direction. The distance between the turns is 65m, and ordinary belt conveyors cannot be laid normally. For example, SGW * 40T scraper machines are required for tandem transportation, with a total power of 160kW. And the sub-lane transfer machine cannot be used. For this reason, the waveform analysis of Chaohua mining technology shows that the high-level width of V4 increases, which causes the low-pass filtered DC control voltage V5 to rise. As a result, the frequency of the voltage-controlled oscillator / 0 will also increase, / 0 is large to equal the system Up to n times the frequency. Conversely, if the grid frequency decreases, it will also reduce / 0, which is still equal to n times the system grid frequency. In this way, / 0 always maintains a fixed frequency multiplication relationship with the system grid, and the synchronization circuit draws the system frequency from the middle of the sub-frequency At 6 times the frequency, the intermediate signal, that is, a pulse with an electrical angle of 60 * per cycle, is used as a six-beat pulse to control the phase shift, which can be triggered in equal intervals and minimize the harmonic component (see).
3 Benefit analysis Since the equipment reconstruction in 1996, not only has greatly reduced the number of faulty personnel combined with the actual situation of our mine, but also made a lot of attempts to actively explore the belt conveyor bending operation theory. After repeated calculations, demonstrations and tests, the clever use of ordinary The body of the belt conveyor has undergone a series of technical transformations to successfully realize the non-mandatory turning of ordinary belt conveyors. At the same time, this achievement was promoted and applied to various types of belt conveyors to avoid the phenomenon of multiple machines in series in the transportation lane with horizontal turns below 8 *. Practice has proved that the use of flexible belt conveyors in curved transport lanes in underground mines has a simplified development system, plus resource recovery, reduced transfer points, saved mechanical and electrical equipment, reduced coal crushing rate, reduced coal dust pollution, and reduced initial investment and operating costs. advantage. Below we will discuss several problems in the design, installation and commissioning of Chaohua Mine's flexible belt conveyor for future design and use.
The main content of the design and transformation of ordinary belt conveyors can not implement mandatory turning, Chaohua Mine adopted three measures in the bending section: basic measures, additional measures and emergency measures.
From the point of view of energy saving, it reduces the warm-up time of about 20 minutes before each start-up, which brings significant economic benefits. From the perspective of national energy policies, this work has practical significance.
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