Abstract: This article introduces the application scheme of Huichuan's sensorless vector frequency converter in slitting machines and the issues that should be noted during debugging. Due to its good torque characteristics and maintenance-free performance, it has been increasingly used in packaging and printing companies. Keywords : Slitting machine, frequency converter, tension control. In recent years, China's papermaking and printing packaging industries have achieved rapid development and are facing unprecedented opportunities. However, compared with the world's advanced equipment, they also face huge challenges. The production capacity of our equipment is very strong, but our products are basically in the low-to-mid-end market. The main reason is the limitation of technical conditions. To date, a large number of slitting machines still use magnetic powder brakes for winding and unwinding tension control, which limits the operating speed of the equipment, wastes energy, and causes a high failure rate due to the limited lifespan of the magnetic powder itself. Huichuan's MD330 tension control frequency converter can perform constant tension control and control the tension taper, ensuring the uniform shape of each layer after winding, and greatly improving the operating speed of the slitting machine. [b]I. Introduction to Slitting Machines[/b] The traditional control scheme for slitting machines uses a large motor to drive the take-up and unwinding shafts. A magnetic powder clutch is added to the take-up and unwinding shafts. The resistance generated by the magnetic powder clutch is controlled by adjusting the current of the clutch, thereby controlling the surface tension of the material. A magnetic powder clutch and brake is a special type of automated actuator. It transmits torque by filling the working gap with magnetic powder. Changing the excitation current alters the magnetic state of the powder, thus adjusting the transmitted torque. It can be used for stepless speed regulation from zero to synchronous speed, suitable for high-speed fine-tuning and low-to-medium power speed regulation systems. It is also used in unwinding or rewinding tension control systems where torque is adjusted by regulating the current to ensure constant tension during winding. Its main feature is that the magnetic powder clutch acts as a resistance device, and through system control, a DC voltage is output to control the resistance generated by the magnetic powder clutch. Its main advantage is that its passive device can control relatively small tensions. Its main disadvantage is that the speed cannot be too high; high-speed operation easily causes high-speed friction of the magnetic powder, generating high temperatures, causing the magnetic powder clutch to overheat and shorten its lifespan. **II. Application of Huichuan Frequency Converters in Slitting Machines** The Huichuan MD320 general-purpose frequency converter is used to drive the pressure rollers and control the slitting machine's operating speed. It can operate in open-loop vector mode. The main speed can generally be adjusted using a potentiometer. The AO1 port serves as the output of the operating frequency, providing the linear speed reference for the unwinding frequency converter and the upper and lower winding frequency converters. The unwinding and winding frequency converters must use the Huichuan MD330 tension-specific frequency converter. All three types of frequency converters need to operate in closed-loop vector mode, specifically in tension open-loop mode. The Huichuan MD330 frequency converter is capable of constant tension control. It can obtain the material roll diameter through internal calculations and achieve constant tension control by controlling the output torque of the frequency converter. The Huichuan frequency converter can compensate for uneven speed during startup or acceleration caused by system inertia, friction resistance, and material inertia by setting system inertia compensation, friction compensation, and material inertia compensation, achieving a very smooth tension control effect. The solution is simple and easy to debug. Furthermore, constant tension control is largely unaffected by speed, enabling high-speed slitting. Because the torque control accuracy of a vector control inverter is above 5% of the rated torque, it's difficult for the inverter to output a small torque when the controlled tension is too low, especially during empty winding. When using a Huichuan inverter for slitting machine control, it's recommended to use a motor that directly drives the spindle without installing a reduction gear. This is primarily because the inverter's control quantity for tension is ultimately the inverter's output torque, which is the product of tension and winding diameter. During empty winding, the output torque is at its minimum. If the reduction ratio is N, the torque converted to the inverter is torque/N. If this is less than 5% of the motor's rated torque, the control will be inaccurate. During commissioning, the closed-loop vector mode of the three inverters for winding and unwinding must be properly configured; otherwise, subsequent torque control cannot be achieved. The most common problems encountered during this process include no encoder signal input, reversed A and B direction connections of the rotary encoder, and incorrect encoder pulse count input. These problems manifest primarily as a large deviation between the operating speed and the input speed, or low-speed motor creep with a significant difference between the operating current and the actual no-load current. In unwinding control, the frequency converter essentially only provides a reverse tension force, so its control precision requirements are not high. Debugging is relatively simple. Regarding reverse tension at zero speed, Huichuan frequency converters offer two options: one is to allow reverse tension, meaning that at zero speed, if the run command is not cancelled, the frequency converter can control the motor to continuously tighten the material, avoiding speed shocks caused by material looseness at the start of operation, which could break the material. The other option is to disallow reverse tightening; at zero speed, if the run command is not cancelled, the frequency converter has no torque output. The material may loosen, but this avoids the possibility of material breakage. The winding frequency converter operates in torque control mode, requiring additional torque to overcome the system's rotational inertia during acceleration and deceleration. Without compensation, tension will be too low during winding and too high during deceleration. If tension decreases at startup, the system inertia compensation coefficient should be increased. Friction compensation mainly overcomes the influence of friction on tension throughout operation, which can be achieved by adjusting the friction compensation coefficient. If the material tension is less than the set tension during normal operation, the friction compensation coefficient will be increased. Additionally, the rotational inertia generated by the material on the reel needs compensation. By setting the material density and width, the inverter can calculate the current rotational inertia. Setting an appropriate tension taper during commissioning can control the material winding quality and prevent a situation where the outside is tight and the inside is loose. In many cases, the reel diameter is obtained through linear speed calculation, and the reel diameter is a direct factor in calculating the output torque; therefore, correctly setting the maximum linear speed is crucial. During commissioning, the accuracy of the set maximum linear speed can be determined by verifying the current reel diameter displayed on the inverter and the actual reel diameter. If the displayed current reel diameter is greater than the actual reel diameter, it indicates that the set maximum linear speed is too high. By setting the above compensation values, the influence of system inertia on acceleration and deceleration can be effectively changed. Setting an appropriate tension can achieve better winding control. Because using frequency converters to control the unwinding and rewinding of slitting machines overcomes the inherent weaknesses of magnetic powder, high-speed slitting control becomes a reality, and equipment reliability is greatly improved without significantly increasing costs. Therefore, more and more customers are adopting frequency converters for slitting machine control. [b][align=center]For details, please click: Application of MD Series Frequency Converters in Slitting Machines[/align][/b]