Application of ANSLE frequency drive in Belt Conveyer.

Frequency drive is a new technology that has only come up in the last few years. It uses changes in the power supply frequency to realize regulation of speed. Because it is able to provide stable speed regulation, instantaneous stability and energy savings, it has received more and more attention. With the maturation of variable frequency speed regulation technology, configuration of this type in belt conveyer equipment is becoming increasingly common. Our MD series belt conveyer variable frequency speed regulation control equipment has the following characteristics:

■ Provides true application of soft start capability in belt-style conveyer systems. By using the frequency converter soft start function, the motor soft start and belt motor soft start are integrated with the slow start of the motor initiating the slow start of the belt motor, lowering fluctuations in tension during the startup process, virtually producing no damage to the belt.

■ Power balance when the belt is driven by multi-motor. When applying the frequency converter to drive the belt motor, one-in-one control is usually chosen and with multi-motor drive, a master/slave control is used to realize power balance.

■ Lowering belt-strength. After using a frequency drive , which allows for startup time to be adjusted between 1S~6,500S, belt motor startup time is usually set at 60S~200S according to on-site settings. If the startup time of the belt motor is increased, the demand on belt strength is greatly reduced, decreasing initial investment in equipment.

■ Reduced need for equipment maintenance. A frequency converter is an integration of electronic equipment. It converts mechanical life to electronic life, which is much longer, greatly decreasing the need for equipment maintenance. At the same time, using the soft start function of the frequency converter to realize soft start of belt-style conveyer means that there is no mechanical impact during the startup process, greatly decreasing the amount of inspection necessary for the mechanical portion of the belt motor system.

■ Smooth startup, high torque, no current rush, able to realize heavy load startup.

■ Energy saving. After using variable frequency drive in belt motors, energy savings is seen in both the system power factor and system efficiency.

a. Increasing the System Power Factor

Usually, the allowance in designing motors for coal mining is relatively large and most do not operate at full load. Motors operate at full voltage and full speed, but loads are usually small and often operate with no load. From the motor design and operation characteristics, we know that the motor will only operate at maximum efficiency and an optimum power factor if it is close to full load. With small loads, this is lowered, creating unnecessary energy losses. This is because with small loads, the stator current power component is very small, mainly the excitation reactive component, which means that the power factor is very low. After using frequency converter drive, the power factor for the system overall reached over 0.9, greatly decreasing reactive power.

b. Increasing System Efficiency

After using the frequency drive, the direct rigid connection between the motor and reducer eliminated fluid coupling. The transmission efficiency of fluid coupling was not very high to begin with, using liquid material to transmit, which is far less efficient compared to a direct rigid connection. Therefore, after using frequency converter drive, the overall transmission efficiency of the system was increased by 5-10% over fluid coupling drive.

In addition, mining shafts are usually relatively far from transformer substation and voltage fluctuation can be rather large during different time periods, so using the automatic voltage regulation function in the frequency drive can also help save energy.

In the above, a belt conveyor variable frequency drive control technology was used to remodel the traditional belt-style conveyor drive system, providing considerably benefiting both advancement in technology as well as social and economic arenas. With the constant maturing of variable frequency speed regulation technology, frequency converters will take a leading position in belt-style conveyer drives.