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About the application of voltage and frequency modulation soft starter in scraper conveyor

Oct 29, 2020

About the application of voltage and frequency modulation soft starter in scraper conveyor

In order to solve the start-up problems of the scraper conveyor for heavy load, start-up dynamic load impact, grid impact, etc., an energy joint-stock company XX coal mine has applied a mine explosion-proof and intrinsically safe voltage and frequency modulation soft start It is mainly used in places where three-phase squirrel-cage asynchronous motors need to be started slowly under heavy load in underground coal mines. It can be used for soft start with frequency modulation and strong torque, and soft start with voltage and current limit. It is used as a hard drive for ordinary magnetic starters. Startup, motor reversal, cut off the power supply, single machine start, multi-machine linkage, multi-machine sequential start.

1 Geological conditions and supporting equipment of working face

1.1 Geological conditions of working face

   The geological structure of the working face is simple, with the 3# coal seam, the thickness of the coal seam is 6.4m, the inclination of the coal seam is 3~5°, the Platts coefficient f=1~2, the bulk density of the entity is 1.3t/m3, and the water inflow of the working face is 5m3/h. Coal roof: the immediate roof is sandy mudstone, and the old roof is siltstone, which is moderately stable. Coal seam floor: sandy mudstone, of medium stability.

1.2 Working face parameters and supporting equipment

   Fully mechanized caving face, the inclined length of the working face is 200m, the inclination angle is 3~5°, the mining height is 3m, the strike length is 690m, and the remaining 250m in August 2002. The working face is equipped with 133 zzPF4404/17/32 type top coal caving hydraulic supports, one MAX-300 type shearer, the rear conveyor is SGZ764/500, and the front conveyor is SGZ764/630.

(1) The main technical parameters of the controlled scraper conveyor: the model is SGZ64/630; the power of the whole machine is 2×315kw; the rated voltage is 1140V; the rated current: 200A; the laying length is 200m; the transportation capacity is 1200t/h; the chain speed is 1 .2m/s; the chain is a medium and double chain specification D30×108.

(2) The main technical parameters of the soft starter

The model is XX type; the rated voltage is three-phase 1140 (660) V; the rated current is 250A; the maximum power of the controlled motor is 400kw; the starting time is automatically set according to the load; the starting current is 4 times the rated current; the current feedback method is greater than or equal to 1 times the rated torque of the motor; strong torque start mode, greater than or equal to 1.4 times the rated torque of the motor.

2 Installation method

Because the soft starter not only has the function of soft start, but also has the function of magnetic starter, so when installing, it will directly replace the original magnetic starter, set one soft starter as the master command, and the other switch as the command, master command The operation control line is connected to the comprehensive control system of the fully mechanized mining face produced by Tianning Company for centralized operation and control of the scraper.

3 The operation of installing soft starters in fully mechanized mining face

In order to evaluate the soft starter's technical performance, adaptability, compatibility with the scraper and the reliability of the equipment, after the product arrives at the XX coal mine, the no-load matching debugging with the ground motor was first carried out, and the operation was carried out at the same time The technical training of the workers has created good conditions for the smooth assembly, putting into operation and subsequent use of the mine. On August 26, 2002, the soft starter was officially put into operation, realizing the soft start control of the front scraper conveyor. At the beginning, no-load trial operation, half-load trial operation, and heavy-duty trial operation of the scraper were carried out. In addition, a detailed observation and recording of the heavy-load start is carried out. The outstanding performance during start-up is: the power grid and the voltage change are very obvious, gradually increasing from 0 to 1160v to the end of the start; the starting current is significantly reduced, which is far less than the magnetic start The overload starting current of the device. During the entire start-up process of the scraper, the scraper is slow and stable, and the start-up time is about 20s; when the scraper is under heavy load, it can start smoothly without any pressure slipping. Since use, we have been observing the start parameters of the scraper, and they all meet the above characteristics.

4 The situation before using the soft starter

Since the working face was put into production in December 2001, it has been using the March 8th manufacturing industry. The daily "0" and "8" shifts are used for production, the afternoon "4" shifts are overhauled for 4 hours, and the production is 4 hours. The main problems that exist before the soft starter is not used when changing coal mining at a working face are:

(1) Frequent chain-breaking accidents: Almost every 2d, the single chain is broken once, consuming 2-4 links, and the double-strand is broken once or the double-strand is broken once a month. It takes 4h to connect the double-strand. It takes 8h to connect the double strand. The labor intensity of the chain workers is very high.

(2) Pressure slips often occur, 1 to 2 times per original shift, forced start after rolling, but can not be achieved several times. At this time, the hydraulic coupler has oil seal damage, easy to dissolve, plug and spray, and general failure The treatment takes 2 to 4 hours.

5 Conclusion

After three months of underground industrial tests, the working face was from August 26, 2002 to November 26, 2002, mainly due to external conditions. The cumulative production of raw coal was 360,000 tons, with an average monthly output of 120,000 tons and an average daily output. 4000t, with a maximum daily output of 6500t. During the test, the soft starter was operating normally. It is believed that this mine-used flameproof and intrinsically safe voltage-regulated and frequency-regulated soft starter is suitable for the special production environment in underground coal mines and can solve the starting problem of the scraper conveyor.

(1) The start-up time is self-adjusted according to the load. The start-up time is extended from the original 5~7s to nearly 20s, which reduces the acceleration by 4 times, greatly reduces the dynamic impact load of the scraper, and effectively protects the scraper. The most obvious transmission and related components are basically the elimination of chain-breaking accidents. The chain has been broken from once every 2d in the past to almost continuous chains, which greatly improves the operation efficiency and start-up rate of the equipment, and reduces the labor intensity of workers. .

(2) Solve the problem that the scraper conveyor is difficult to start under heavy load. Using this soft starter in conjunction with the overload alarm system, the normal start can be achieved without the pressure slipping problem, which improves the operating efficiency of the conveyor and protects the equipment , Reducing the labor intensity of workers.

(3) The starting current of the conveyor is very large, causing the grid voltage to drop suddenly, affecting the power supply quality of the grid, affecting the normal operation of other equipment, and affecting the service life of the grid power supply equipment. These are all caused by high-power motors and large currents that impact the grid. Caused by. After the soft starter is put into operation, the starting current is greatly reduced, which improves the power supply quality of the power grid and reduces the impact of the power grid.

   (4) Compared with other soft start devices, the outstanding features of this soft starter except for the same points are: ① All realize electrical soft start control. Convenient and simple to use, and the reliability of the system is obviously improved; ②The magnetic starter and the electrical soft start are combined into one, which simplifies the equipment layout, and also has overload, undervoltage, phase loss, leakage lockout, and short circuit protection; ③ The control mode can be divided into remote control and on-site control, which facilitates the connection control with other operation consoles; ④The start mode is divided into two modes: pressure regulating soft start and strong torque soft start.