The load of the conveyor drive device is a typical constant torque load, and it is inevitable to start and brake with load, that is, to start and stop at full capacity. The starting characteristics of the electric motor are not suitable for the starting requirements of the load, which is particularly prominent on belt conveyors. On the one hand, in order to protect the required starting torque, the current during motor starting should be 6-7 times higher than the rated operating current. To protect the electric motor from overheating due to current impact and prevent excessive voltage reduction in the power grid due to high current, it is necessary to start the electric motor as quickly as possible, that is, to increase the acceleration of the rotor, Ensure that the starting process does not exceed 3-5 seconds. In order to achieve this, the method of increasing the power of the electric motor has been used in the past, which can also be used for small and short belt conveyors

On the other hand, conveyor belts are a type of viscous body. During the unstable stage of starting and braking, the traction, braking, and inertia forces applied by the driving device to the conveyor belt will propagate, stack, and reflect within the belt at a determined wave speed, causing polygonal stress changes within the conveyor belt. If the instantaneous peak stress exceeds the allowable value, it will damage the conveyor belt or even cause it to break, or cause early damage to the rollers and drums, This requires a minimum starting and braking acceleration to reduce the impact during starting and braking. The starting acceleration of modern belt conveyors is required to be controlled between 0.1~0.3m/s. The stress changes that occur on the conveyor belt during the parking brake of a large belt conveyor are sometimes even more severe than during start-up. To solve this contradiction and regulate the impact on the electric motor, hydraulic couplings, CST controllable reducers, and controllable drive systems are often used