Study Of Electromagnetic Variable Speed Braking Technology For Downward Belt Conveyor

Belt conveyor is considered to be the most economical,reliable and important equipment in mine production in china. The stopping device is undoubtedly the most crucial part of a downward belt conveyor. It is thus obvious that the performance of a downward belt conveyor depends largely on the performance of the braking system used.The problems are described when brake system is used to bring the downward belt conveyor to a halt in this paper and a control system of electromagnetic speed regulation for the conveyor is studied. The system, based on electromagnetic technology, exclude the work oil which is easily polluted by the harsh environment underground and overcome the shortcoming of traditional electromagnetic speed regulation motor to guarantee conveyor's safe brake.A simplified uniaxial drag model of the electromagnetic speed control system is put forward according to the working principle and mechanical properties of electromagnetic adjustable-speed motor. Then the transfer functions of system is established and analyzed in frequency domain to provide a theoretical basis. In order to improve the accuracy of the system and overcome the velocity measurement error of tachogenerator, the sampling signals collected by the Bidirectional axle coder and Hall Effect transducer are processed in the way of average value method by the high speed counter of PLC.The operation capacity, braking capacity and anti-interference ability of the downward belt conveyor are improved greatly by the electromagnetic speed control system with the double-close loop of speed and current. The curve of brake would meet the ideal requirement under the control of excitation current which is regulated by the double-close loop of current and speed.