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When a belt conveyor stops transporting material due to some reason and is started again, it constitutes a start under heavy load. The frequency converter is required to enable the belt conveyor to start under heavy load with material on it. Next, the editor from Shanghai Yuyin Machinery will summarize for you the requirements for restarting a belt conveyor while it is carrying material. The torque caused by the downward pull of the material on the belt is constant. However, static friction is much greater than dynamic friction, which means that the initial starting torque required to overcome static friction is much larger than the resisting torque caused by dynamic friction during normal operation. When a belt conveyor starts under heavy load with material on it, the torque generated by the motor must not only overcome the resistive torque caused by the static friction between each support roller and its axle beneath the belt, but also overcome the resistive torque resulting from the downward pull of the material on the belt. Moreover, during the entire startup process of the belt conveyor, it takes some time for all the rollers to start rotating before the torque begins to decrease. Only by reaching a certain speed can lubrication be improved, and torque fluctuations will decrease. The frequency converter for belt conveyors must have the capability to provide high starting torque at low speeds. In reality, during startup, due to the elasticity of the belt, each roller rotates one after another in sequence, and they do not rotate simultaneously. Even when the roller starts to rotate, due to the low speed, the lubrication between the roller and its axle is poor, resulting in significant friction; moreover, the dynamic friction force is unstable, which causes fluctuations in torque during startup at low speeds. Therefore, the high low-speed starting torque of belt conveyors needs to be maintained for a certain period of time, usually at least a few seconds. It is related to factors such as the length of the belt, the minimum speed at startup, and the elasticity of the belt. Moreover, during startup, due to the low speed, the fluctuations in torque and speed are relatively large.