The traction machine is generated by the traction force acting on the traction sheave groove by the hoisting rope together with the weight of the counterweight. The counterweight is a necessary condition for the friction between the hoisting rope and the traction sheave rope groove. With it, the traction machine is easy to balance the weight of the car with the weight of the payload, which also reduces the power consumption of the transmission when the elevator is running. Therefore, the counterweight, also called the counterweight, is suspended from the other end of the traction sheave to balance the weight of the car.

       When the car side weight is equal to the counterweight side weight, T1=T2. If the traction machine does not consider the change of the wire rope weight, the traction machine can easily operate by overcoming various frictional resistances. However, the weight of the car actually varies with the cargo (passenger), so the fixed counterweight cannot completely balance the weight of the car under various loads. Therefore, the weight and weight of the counterweight will directly affect the traction and transmission power.

        In order to make the elevator full load and no load, the absolute value of the load torque is basically equal. The national standard of the traction machine is K=0.4~0.5, that is, the counterweight is 40%~50% of the rated load. Therefore, the total weight of the heavy side should be equal to the weight of the car plus 0.4 to 0.5 times the rated load. This 0.4~0.5 is the balance factor.

        When K = 0.5, the load torque of the elevator is zero at half load. The car is fully balanced with the counterweight and the elevator is in optimal working condition. When the elevator load changes from no-load (no-load) to rated load (full load), the torque reflected on the traction sheave changes only 50% of the soil, reducing energy consumption and reducing the burden on the traction machine.

Equivalent friction coefficient f and rope groove shape
       When the hoisting rope is in contact with the differently shaped rope grooves of the traction sheave, the frictional force generated by the hoisting machine is different, and the greater the frictional force, the greater the traction force. There are several types from the current use: semi-circular grooves, V-shaped grooves, and semi-circular grooves with slits. The semi-circular groove f is the smallest for the rewinding traction sheave. The V-shaped wheel f is the largest and increases as the opening angle decreases, but at the same time the wear also increases, and the traction rope is worn and the rope is pulled. As the wear will tend to a semi-circular groove. The semicircular notch groove f is between the two, and it does not change substantially with wear, and is currently widely used. The lubrication of the steel wire rope in the rope groove also directly affects the friction coefficient. Only the oil core in the rope can be slightly lubricated. The lubricating oil should not be applied outside the rope to avoid reducing the friction coefficient, causing the slip phenomenon and reducing the traction force.

Wrap angle of the traction rope on the traction sheave
       The wrap angle refers to the arc of the traction wire rope that passes through the rope groove. It means that the larger the wrap angle is, the larger the friction force is, and the traction force of the traction machine is also increased, which improves the safety of the elevator. Increasing the wrap angle currently uses two methods. One is to use a 2:1 drag ratio to increase the wrap angle to 180°. The other is a rewind type (α1+α2).

        The method of winding the rope of the elevator traction rope mainly depends on the traction conditions, the rated load capacity and the rated speed. It has a variety of them. These winding methods can also be regarded as different transmission modes. Different winding methods have different transmission speed ratios, also called traction ratios. It is the ratio of the linear speed of the traction wheel pitch circle to the running speed of the car when the elevator is running. . The number of times the wire rope is wound on the traction sheave can be divided into single winding and rewinding. When the single wire is wound, the wire rope is only once wound on the traction sheave, and its wrap angle is less than or equal to 180°. When the traction machine is rewinded, the wire rope is dragged. The guide wheel is wound twice and its wrap angle is greater than 180°