When the belt conveyor belt for some reason to stop, and then start when the load is heavy start. The frequency converter can be used for belt conveyor with heavy load start. The belt machine on the strip for heavy start, the output torque of the motor, to overcome the static friction between the torque caused by the belt below each of the supporting rollers and roller shaft, to overcome the resistance moment of the materials caused downward pulling force on the belt. The resistance of the material to the pull of the belt is constant. However, the static friction force is much larger than the dynamic friction force, which makes it possible to overcome the static friction force of the initial starting torque, than the normal operation of the friction force caused by a large number of resistance moment. So the inverter must have the function of low speed and large starting torque. In fact, in the process of starting, because of the flexibility of the belt, each roller is rotated one by one in sequence. Even if the roller rotation, because the speed is very low, the wheel and the roller shaft lubrication is not good, it will be very astringent, the dynamic friction is unstable, so the torque at low speed start has a certain fluctuation. And in the entire start-up process, it takes a certain amount of time, so that all the wheels are turned up, the torque began to decline. Only to achieve a certain speed, improve lubrication, torque fluctuations will be reduced. Therefore, this large low-speed start torque, is the need to maintain a certain amount of time, usually at least a few seconds. And the length of the belt and the minimum rotation speed, as well as the expansion of the belt and so on. And because of the low speed, torque and speed fluctuations will be relatively large.