Utilizing of multi-drive belt conveyor is widely used in the mining transportation system.
During the starting process, if the soft start equipment is not applied, the belt conveyor will be damaged easily due to the big tension vibration. In another hand, if we start the motor directly, the start current will be 4~7times of the motor rating current, this big surge current will change the internal mechanical stress and thermal stress of motor, and cause serious abrasion and damage to the mechanical part. Meanwhile, the big surge current will cause big voltage drop of the grid, and effect other equipment's operation.
The frequency inverter controlled system consists of two NOS of KE600 inverter, weight sensor, PG card, encoder etc. Normally, it needs to upgrade the both terminals'motors, the system diagram is shown as below:
The two inverters are common DC bus connected, the regenerated energy can be reused internally.
One frequency inverter set as master, another one set as slave, because the belt conveyor is flexible connection, the master-slave motors can be controlled by speed.
The master inverter receives the 4-20mA signal from weight sensor to calculate its output frequency, this frequency signal will output to slave inverter as it frequency reference, to achieve the synchronous speed and balanced power of the two motors.
Both of the master and slave system are close-loop vector control mode, to get significant starting torque.
The braking unit of energy feedback unit are necessary for down-running belt conveyor.