Application of FGI FD5000 Medium Voltage Drive in Continuous Conveyors

A conveyor is a material handling machine that continuously conveys materials along a certain line, also known as a continuous conveyor. Conveyors can be horizontal or inclined, and can also form spatial conveying lines. The conveying lines are generally fixed. Xiaolongtan Mining Bureau of Yunnan Province is a state-owned coal production enterprise. It is one of the key mining areas of the large-scale coal base approved by the state - the Yunnan-Guizhou Coal Base. It is an important energy production base in Yunnan Province, mainly producing lbrown coal. It has two open-pit coal mines, Xiaolongtan and Buzhaoba, as well as units for machinery repair and construction. The mining bureau has developed a business pattern mainly based on coal and featuring multiple industries. Besides the coal industry, it also has sectors such as machinery repair, construction, processing, and services, demonstrating a strong development momentum. The ongoing fifth-phase expansion project is a key construction project of Yunnan Province's "Double Hundred" initiative. It officially started full-scale construction in March 2008. Once completed, the coal output will reach 14.9 million tons per year.

1. Project overview and design scheme

The main motor power of the 502 belt conveyor in the new stripping system of Buzhaoba, Xiaolongtan Mining Bureau, Yunnan Province is 2x800kW. To ensure safe production and reduce the impact on the equipment, the mining bureau, in collaboration with the design and maintenance departments, has decided to adopt a high-voltage frequency converter for drive. Moreover, in order to deal with the relatively large errors in the mechanical part, taking advantage of the convenient speed regulation feature of the frequency converter, a one-to-one and dual-machine synchronization method is adopted.

2. The working principle and features of the system belt conveyor

The belt conveyor drives the drum wheel and pulls the belt to move by friction. The belt deforms under tension and drives the object to move on the supporting roller wheel through friction. Tape is an elastic energy storage material. It stores a large amount of potential energy when the belt conveyor stops and runs. This determines that a soft start method should be adopted when starting the belt conveyor. Most domestic coal mines use hydraulic couplings to achieve the soft start of belt conveyors. During the start-up process, the mechanical efficiency of the hydraulic coupling is adjusted to zero to enable the motor to start without load. When using a hydraulic coupling for the soft belt conveyor, due to the narrow speed regulation range, the start-up time is short and the loading force is large at low speed. Meanwhile, when the front and rear dual machines drive the same belt to work, it is difficult to truly solve the distribution and synchronization problem of the load power and the elastic potential energy power of the belt, which is prone to cause belt breakage and aging. Therefore, the belt strength is required to be high. In addition, long-term operation of the hydraulic coupling can cause the internal oil temperature to rise, wear of metal parts, leakage and reduced efficiency, etc. This not only increases the difficulty and cost of maintenance, but also pollutes the environment.

3. Program implementation

The dual-machine communication processing system coordinates and controls the master and slave frequency converter systems, communicating with each other and exchanging information. The DCS system sends the operating frequency to the communication system. The communication system then transmits the given rotational speed to the host machine, which in turn communicates and transmits it to the slave machine. When the main unit has a minor fault, the slave unit will follow the main unit and take corresponding measures in real time. Similarly, when the slave unit has a minor fault, the main unit will also follow the main unit in real time and take response measures. At the same time, with the help of the dual-motor power detection and processing system, the synchronous operation of the main and slave motors is automatically adjusted in real time, truly achieving the synchronous operation of the main and slave units' speeds.

4. Selection of frequency converter

The model of the frequency converter is: FGI FD5000 Medium Voltage Drive, with a rated power of 850KW, a rated voltage of 6KV, and a rated current of 100A. The quantity is 2 units.

The main circuit of the frequency converter is as follows:

Each frequency converter contains a complete set of QS1, QS2, KM1 and KM2.

QS is a single-pole disconnector and KM is a vacuum contactor.

When KM is in the closed state, QS is mechanically locked and cannot be operated.

KM is controlled by the DCS system for closing. The closing state adopts electrical holding, and its coil has the ability to be energized for a long time.

5. Mainly manifest in:

Soft start and soft stop at startup have been achieved, reducing the impact on the power grid.

The continuous frequency adjustment of the frequency converter makes the speed regulation more convenient and reliable, and the operation more stable.

After using the frequency converter, the original shift contactor and speed regulation resistor were eliminated, which not only saved maintenance costs but also reduced the downtime for maintenance, thereby increasing production. At the same time, the harsh operating environment has been improved, enabling workers to avoid working under high-temperature conditions where the speed regulation resistor overheats in summer.

The energy-saving effect is very obvious at low speeds.

6. Analysis of Electricity Saving Rate and Return on Investment

The main motor power of the 502 belt conveyor in the new stripping system of the Buzhaoba of Xiaolongtan Mineral Bureau is 2x800kW. The speed is switched by an AC contactor. Due to the relatively large power, the inrush current is large when starting and shifting gears, and the operation at medium and high speeds is unstable. A large amount of electrical energy is consumed on the rotor resistance, resulting in a huge waste of energy. Meanwhile, the working environment for the workers is extremely harsh and urgently needs to be renovated.

Due to the advantages of the frequency converter such as soft start, smooth speed regulation over a wide range, and significant energy-saving effects, after extensive investigation, our mine has decided to use the FD5000 medium voltage drive produced by FGI Company to carry out frequency conversion transformation of the system. After several months of operation, it has been proved that the transformation effect is relatively ideal.