The Application of FGI FD300 high-performance Vector Frequency Converter in the Belt Conveyor of Coal Washing Plant
Belt conveyors are the main equipment to ensure high output and high efficiency in modern coal mines. The successful application of the FGIFD300 high-performance vector frequency converter on the belt conveyor in coal mines demonstrates its excellent vector control and master-slave synchronous control characteristics. It has very practical economic and social significance for building an energy-saving society and increasing the economic benefits of coal mining enterprises.
1.Introduction
Traditional belt conveyors operate using a constant-frequency power supply method. Due to the long-term operation of the motors at constant frequency and issues such as the efficiency of the hydraulic couplings, the operation of the belt transporters becomes very uneconomical. At the same time, because the motors cannot be started or stopped softly, severe mechanical shocks occur, accelerating the wear of the machinery. Moreover, problems such as the wear and maintenance of the belts and hydraulic couplings will also bring significant costs to the enterprise. The transformation of belt conveyors in coal mining enterprises to variable-frequency operation has very practical economic and social significance for saving social energy and increasing the economic benefits of coal mining enterprises.
2.Requirements for frequency converter technology in belt conveyors
A belt conveyor, also known as a belt conveyor, belt-type conveyor, rubber belt machine, or rubber belt conveyor, is a transmission machinery widely used in mines, chemical plants, and cement factories.
A belt conveyor is composed of a driving device, a tensioning device, a middle frame of the conveyor belt, and idlers. The conveyor belt serves as the traction and load-bearing component, enabling the continuous transportation of loose materials or finished products. The general belt conveyor consists of a conveyor belt, idlers, rollers, and driving, braking, tensioning, redirecting, loading, unloading, and cleaning devices.
The working principle and characteristics of belt conveyors: The belt conveyor moves by the driving wheel drum, relying on friction to pull the belt. The belt moves through the tension deformation and friction force on the supporting rollers. The belt is an elastic energy storage material. When the belt conveyor stops or operates, it stores a large amount of potential energy, which determines that the belt conveyor has increasingly higher requirements for the driving technology when starting. The basic requirements are as follows:
(1) Simple control, excellent starting characteristics, good speed regulation performance, and large starting torque;
(2) Energy saving;
(3) Reliable operation, with low maintenance requirements;
(4) High cost performance.
In current applications, comparisons of various starting methods:
(1) Direct start: It has a large output torque, but the force distribution is uneven, and the tail response is slow. There is a phenomenon of accumulation at the bottom of the belt.
(2) Hydraulic coupling start: The belt conveyor starts slowly, and when a certain torque is reached, the belt begins to operate. During the start-up process, there is a slipping phenomenon, which is prone to cause safety hazards.
(3) Soft start: The belt conveyor starts smoothly when unloaded, with reduced torque and reduced impact. It can extend the service life of the motor, the conveyor belt machine, and the mechanical system, but when under heavy load, it needs a sudden jump, causing greater impact on the conveyor belt machine.
(4) Frequency conversion speed regulation: Due to the wide speed regulation range of the frequency conversion device, it has a large starting torque and can start slowly under heavy load. The starting safety is high, and it has good synchronization performance for multiple motor drives. After matching with logistics sensors, it can automatically adjust the speed according to the size of the logistics, which can generally save energy and significantly improve the motor power factor.
3.Scheme Design and Explanation
This article provides an example based on the on-site requirements of two 380V/160KW motors driving a belt conveyor in a coal washing plant. The customer requested that the two motors have the same output power to solve the problem of unbalanced current that frequently occurred during the original industrial frequency operation.
The core issue of the multi-machine variable frequency speed control system for the belt conveyor is the synchronization of the rotational speeds of the motors and the torque balance. In practical applications, considering the need for full-load startup after a fault shutdown, when selecting a frequency converter, the first thing to consider is a vector control type frequency converter. The multi-machine synchronization also requires the frequency converter to have excellent master-slave control functions. For this, the FD300 series vector frequency converter is the best choice. This series of frequency converters has the following outstanding features:
A. Starting torque: 0.5Hz/150% (SVC); 0Hz/200% (VC)
B. Overload capacity: 150% rated current for 60 seconds; 180% rated current for 10 seconds
C. Speed ratio: 1:100 (SVC); 1:1000 (VC)
D. Speed control accuracy: ±0.5% at the highest speed (SVC); ±0.1% at the highest speed (VC)
E. Frequency setting methods: digital setting, analog setting, high-speed pulse, multi-speed setting, UP/DOWN terminal setting, Modbus remote communication setting, Profibus communication setting, master-slave mode setting, graded multi-speed setting;
For the 160KW dual-drive belt conveyor, considering the torque requirements during startup and operation, a certain gear can be selected to match the frequency converter for it. The selected model is FD300-185G/200P-4. The two motors on site drive the belt to convey coal through two rollers. Therefore, two frequency converters of the same power are selected. The frequency converters are synchronized running through the master-slave control mode. Given that the load connection of the belt conveyor is through a flexible connection, there is a certain degree of flexibility, and there can be a certain speed error between the master and slave machines.
4.Operating Efficiency
A certain coal mine has adopted frequency converters to drive the belt conveyor, and the operation has been very good, demonstrating the following advantages:
1) Synchronous speed and balanced current. The output torque of the slave machine is the same as that of the master machine, and the current is comparable. The current display on the keyboard shows a difference of about 5A. The slave machine will not experience the phenomenon of overvoltage due to mismatch in speed with the master machine.
2) Simple parameters. There are not many parameters to be set and adjusted, and the motor parameters are relatively sensitive. As long as the communication is normal, it is very suitable for the master-slave mode with one master and multiple slaves.
3) Excellent soft start/stop characteristics. The acceleration/deceleration time (0-60min) can be continuously adjusted, and S-shaped acceleration/deceleration can be achieved, effectively reducing the impact of start/stop.
4) Smooth heavy-load startup. The belt conveyor can stop and restart at any time during coal transportation without any problem. At low frequency, the maximum output torque can reach 1.5 times the rated torque.
In conclusion, the FD300 frequency converter, as the power drive equipment for the coal mine belt conveyor, with its high efficiency, low noise, large starting torque, high reliability, excellent speed regulation performance, and maintenance-free advantages, has a broad application prospect in coal production.
