The Role Of Magnetic Powder Brake In Tension Control System

In the tension control system, the magnetic powder brake has been widely used because of its small size, light weight, small excitation power, and good control characteristics. The relationship between magnetic powder brake torque and excitation current is generally referred to as static characteristics. It is the constant speed n of the active end of the magnetic powder brake. When the driven end brakes, the relationship between the excitation current and the output torque of the magnetic powder brake.

As can be seen from the above figure, the torque curve of the magnetic powder brake can be divided into three parts: a non-linear section, a linear section and a saturation section. The magnetic powder brake has good constant torque characteristics, and the magnetic powder brake output torque has a good linear relationship with the magnetic powder coil excitation current. As long as the excitation current is linearly adjusted, dynamic control of the field tension can be achieved. The performance is also very stable. The application of magnetic powder brake in the winding tension control system. As shown in Figure 4, the scheme of using magnetic powder brake to control the tension has the characteristics of simple structure, low cost of the execution unit and easy control compared with the previous control system, especially the actual tension is passed through the current Direct adjustment changes the manual operation process of other adjustment devices, making the operation simple and accurate. Increasing the dynamic current compensation link is helpful to further improve product quality.

The tension control system is often a system integration of tension sensor and tension controller. At present, it is mainly used in metallurgy, papermaking, film, dyeing and finishing, weaving, plastic, wire and other equipment. It is a kind of constant tension or taper tension control. Automatic control system, its role is mainly to achieve synchronization between the rolls, winding and unwinding uniform control.

 Tension sensor control mode:

1. Manual control, continuously adjusting the clutch or brake torque during the receiving, unloading or process, so as to obtain the required tension. This requires the user to check the tension of the controlled material at any time and adjust the output torque at any time. For brakes or clutches, manual controllers can directly select precision pressure regulating valves, which can save users a certain amount of equipment costs, but only suitable for some low-speed compound machines, extruders, textile machinery and other places where tension control requirements are not high.
2. Semi-automatic method: Use the ultrasonic principle to automatically detect the coil diameter to adjust the coil tension. For example, the U.S. Montalvo (Montevo) company U3500 ultrasonic tension controller is essentially a semi-closed loop control of tension. Not only can automatically measure the warp and control the torque output, but also has the functions of buffer start, anti-loosening and inertia compensation. The implementation cost of this solution is low, so it is widely used in mid-range machinery.
3. Fully automatic method: Generally, there are two detection methods. One is to measure the tension of the coil through a tension sensor, and then the clutch or brake is automatically adjusted by the controller to control the tension of the coil. This method is the full closed-loop control of tension. In principle, this solution can reflect the change of tension in real time and therefore has the highest control accuracy. Therefore, some high-end finishing mills, high-speed slitters and other metallurgical systems use fully automatic tension control systems.