Application of three-stage frequency conversion hi

Application of three-stage variable-frequency high-voltage soft start of main fan in Xinyuan mine

Abstract: This paper introduces a kind of load sensor on the loading actuator that realizes step-by-step variable-frequency and stepless adjustment by controlling the thyristor to ensure the accuracy of the loading force value; The spindle mechanism is driven by the control Electromechanical, and the ball screw runs along the x-axis. The displacement is controlled by the high-precision displacement measuring mechanism. The soft starting device and its application in the main fan of large coal mines

key words: three-level frequency conversion, soft starting device

due to the particularity of coal production, the mine ventilation system is related to the safety production of the mine, so the ventilation system plays an important role in coal production. Due to the long power supply line and large starting voltage drop, it is the top priority to ensure the safe and reliable fan starting and main and standby switching starting of the equipment to the greatest extent, which is to enhance the reliability of the system. In November, 2006, the main fan newly put into operation in Xinyuan mine of Yangmei group was GAF axial flow fan (the fan causing impact was inquired to be the largest fan in Asian coal mines). The motor of the main fan is 10kV 5000kW asynchronous motor. In order to better solve the impact of starting on electricity and load in the project, the system adopts the three-level variable-frequency high-voltage soft starting equipment independently developed and produced by Liaoning Rongxin Power Electronics Co., Ltd

1. Several starting modes of soft starter

are divided according to the starting principle of motor: 1. Step down starting mode. The traditional decompression starting mode of the motor is y- Δ Starting, autotransformer decompression starting, reactor starting, etc. These starting methods belong to step-by-step decompression starting, which has obvious disadvantages, that is, there is a secondary impulse current in the starting process. At present, the common starting methods of high voltage are liquid water resistance starting and thyristor series decompression starting. 2. Variable frequency starting mode. With the development of IGBT technology, the voltage level and capacity of high-voltage frequency conversion are becoming larger and larger, but its development has been restricted by the price factor

and improved the physical properties of metal

Rongxin Power Electronics Co., Ltd. has successfully developed a three-stage variable-frequency high-voltage soft start based on SVC, which has the characteristics of three-stage variable-frequency stepless voltage regulation

2. Technical principle and characteristics of three-stage variable frequency high-voltage soft start

the high-voltage soft start is connected in series between the power supply and the motor. See Figure 1 for the principle of the main circuit

Figure 1 Schematic diagram of main circuit

three stage variable frequency high voltage soft start first adopts thyristor series technology, and then realizes the functions of stepwise frequency modulation and stepless voltage regulation by controlling the conduction angle of thyristor. At the initial stage of starting, the primary frequency of 12.5hz is achieved by controlling the conduction of valve groups SA, Sb and SC. when the motor reaches 1/4 of the rated speed, it is switched to 25Hz by controlling valve groups SA, SD and se. After the motor reaches 1/2 of the rated speed, the full frequency switching process is completed by controlling valve groups SA, Sb and SC. finally, the rated speed is reached, the bypass is closed, and the soft start trigger pulse is closed to complete the starting process. In the whole starting process, at three frequency points, while adjusting the frequency, change the output voltage and keep the voltage frequency ratio constant, so that the starting torque can be maintained at% of the rated torque and the starting current can be controlled at about twice the rated current. Large starting torque and small starting current are the biggest technical characteristics of three-stage variable-frequency high-voltage soft start

3. Practical application of main fan motor in Xinyuan mine

Xinyuan mine of Yangmei group is a newly-built mine, with a capacity of 35kV and 10000kva. Since this power is responsible for the power supply of electrical equipment in the whole underground and on the shaft, the margin of electricity is relatively small. In order to ensure that the operation of other equipment is not affected during the starting process, the starting current of the main fan is strictly required. And because it is located in a high gas area, it adopts an axial flow fan with large air volume and high negative pressure (the two-stage fan blade is currently the largest axial flow fan used in mining in Asia), and the power of the main fan motor is 10kV, 5000kW. In the whole starting process, it shows the advantages of large starting torque, small starting current, stable starting and short starting time. See Table 1 for measured data

date blade stage blade angle starting maximum current starting time normal current after starting 10.20 primary blade-151.8ie25s80a-101.8ie28s100a-52ie30s150a02ie33s180a secondary blade-152ie25s200a-102ie30s240a-52.3ie35s300a02.4ie38s340a

4. Conclusion

the system was officially put into operation in November 2006 and has been in good operation without any fault up to now. It has found a starting equipment with high performance and high cost performance for large mining electrical equipment in the future

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