Application of Sunwoele VFD (Variable-frequency Drive) on the belt conveyor of Xinjiang Coking Coal Group

I. Overview

With the continuous maturity and improvement of variable frequency speed regulation technology at home and abroad in modern China, VFD (Variable-frequency Drive) has a wide speed regulation range, high precision, smooth speed regulation, stable and reliable speed regulation, hard motor speed regulation characteristics, and significant energy saving effects. Features, gradually replacing traditional DC speed control and hydraulic coupling, liquid resistance and electromagnetic speed control equipment. Widely used in metallurgy, petroleum, chemical industry, cement, mining and other fields. Chengdu Sunwoele HFV3000 high-voltage VFD (Variable-frequency Drive) is in a leading position in the domestic high-voltage frequency conversion industry because of its unique and distinctive features such as advanced control technology, powerful control functions, safety and reliability. Xinjiang Coking Coal Group selected the HFV3000 VFD (Variable-frequency Drive) through a tender to be used in the control of coal mine inclined shaft belt conveyors. After nearly two years of operation, the operation has been safe, stable and reliable, and has produced good economic benefits.

2. Working environment and working conditions

The mining area of Xinjiang Coking Coal Group is located in a mountainous area with an altitude of 2000 to 2200m. The highest ambient temperature in summer is 41°C and the lowest temperature in winter is -30°C. The mining area has three wellheads with an annual output of 1.2 million tons. Xinjiang Coking Coal Group's gas and coal inclined shaft uses an inclined shaft belt conveyor to transport coal from underground to the surface. The daily coal production is about 3500t. The belt length is 650m, the belt inclination angle is 19°~24°, the belt drive motor is 400kW, and the power supply is 6kV dual power supply. These working conditions require the motor starting control equipment to operate stably and reliably in high altitude areas, and at the same time, it must have strong overload capability and be able to adapt to a wide range of voltage fluctuations.

The original design of the belt motor was for direct starting. Later, it was considered that direct starting of the motor would have a great impact on the power grid and transmission machinery and equipment, and it would always be running at full speed, which was not conducive to saving energy consumption. After careful research and comparison of various high-voltage VFDs (Variable-frequency Drives) at home and abroad, Chengdu Sunwoele's HFV3000 high-voltage VFD (Variable-frequency Drive), which has advantages in cost performance, product quality and service, was finally selected as the belt through bidding. Control equipment for transport aircraft.

3. Usage

Considering factors such as high altitude and high ambient temperature in summer, appropriate margin should be left when selecting VFD (Variable-frequency Drive). The motor power is 400kW, the rated voltage is 6kV, and the rated current is 38.49A. Xinjiang Coking Coal Group selected Sunwoele VFD (Variable-frequency Drive) HFV3000-Y06/061 with a rated voltage of 6kV and a rated current of 61A to control a 400kW belt motor. The VFD (Variable-frequency Drive) is equipped with an automatic bypass cabinet so that it can automatically bypass to the grid power frequency operation when a fault occurs to ensure continuous and uninterrupted production. After the bypass operation, the VFD (Variable-frequency Drive) input can be easily cut off. The output side isolating switch and vacuum circuit breaker enable the VFD (Variable-frequency Drive) to be isolated from the high-voltage power supply, allowing for easy maintenance. The VFD (Variable-frequency Drive) was debugged and put into use in April 2006. It has not experienced any downtime and is running in good condition.

The VFD (Variable-frequency Drive) cooling fan dissipates heat well. However, due to the large amount of coal ash and dust on site, the dust on the heat dissipation device needs to be cleared regularly. Measures to reduce environmental dust are currently being addressed. Due to the use of multiplexed pulse width modulation technology and series superimposed wave output, the output waveform is not distorted, close to a perfect sine wave waveform, no harmonic pollution, and no filtering device is required. It meets the power department’s control requirements for the harmonic content of the power grid. There is no interference to surrounding electrical equipment and nearby belt conveyor comprehensive protection devices. It reduces motor noise and heat, does not cause motor torque pulsation, and has no special requirements for the motor. The operating power factor can reach more than 0.95, and the efficiency can reach more than 96%.

Based on the powerful control function, simple and intuitive operation method, stable and reliable operation of the HFV3000 high-voltage VFD (Variable-frequency Drive), and its successful application in the gas wells of Xinjiang Coking Coal Group, the HFV3000 high-voltage VFD (Variable-frequency Drive) is favored by Xinjiang Coking Coal Group. When the 2130 mine was expanded in July 2006, the Coking Coal Group selected a set of HFV3000-Y06/077 (800kVA) high-voltage VFD (Variable-frequency Drive) for the control of the belt conveyor in the 2130 mine. The gas coal mine plans to expand its production, and plans to increase the belt transportation capacity and change the original belt conveyor to a dual-machine drive. In September 2007, the gas coal mine added another set of HFV3000-Y 06/061 VFD (Variable-frequency Drive).

4. Working principle

HFV3000 VFD (Variable-frequency Drive) adopts AC-DC-AC voltage source type. Apply mature low-voltage frequency conversion technology, advanced unit series stacked wave structure, and space vector controlled sine wave PWM modulation method. Each phase consists of 5 power units connected in series. The high-voltage 6kV power supply is directly input to the high-voltage side of the isolation transformer. The secondary side of the transformer outputs three-phase 690V voltage after step-down and phase-shifting to supply power to each power unit respectively. The power unit goes through three stages of three-phase full-bridge rectification - DC filtering - single-phase inverter output, and then each unit of each phase is connected in series, and the three-phase star connection directly outputs high-voltage 6kV to drive the motor. The input side is equivalent to 30-pulse rectification, and the output side is equivalent to 11-level stack waves per phase. The input and output are both