Views: 67 Author: Site Editor Publish Time: 2024-04-24 Origin: Site
The application of variable frequency speed regulation technology in the textile industry is extensive, and its presence can be seen in various spinning and weaving machinery. Applying variable frequency technology to textile equipment can not only improve production efficiency and automation levels but also reduce the intensity of labor for workers. It can enhance automatic energy-saving operation, increase energy-saving rates, and provide various functions such as continuous operation during instant power outages and synchronous acceleration and deceleration of conveyor belt speeds. Below are examples of the application of variable frequency drives (VFDs) in the textile industry.
Due to the potential speed discrepancy between the winding section of the roving frame and the front roller during start-up and stoppage, excessive or insufficient tension in the roving can easily occur, leading to variations in roving thickness. To mitigate this issue, preventive measures are incorporated into the design of roving frame transmissions, such as reactors, time relays, and electromagnetic clutches.
Reactors primarily address the unbalanced three-phase state of the motor during roving frame start-up, reducing the motor's starting torque to achieve soft start-up. Time relays and electromagnetic clutches, on the other hand, disengage the turret from the winding cylinder during roving frame shutdown, halting cylinder winding while the front roller continues to output roving due to inertia. This arrangement allows for a certain degree of relaxation between the roller and spindle wings, preventing excessive tension when restarting the roving frame.
However, these preventive measures exhibit significant drawbacks in practical use. Firstly, reactors are connected in series with one phase of the three-phase circuit, leveraging the principle of three-phase imbalance to reduce the motor's starting torque. Upon completion of roving frame start-up, the time relay short-circuits the reactor to restore the motor to a balanced three-phase state and initiate normal operation. Any malfunction in the time relay can lead to prolonged operation of the motor in an unbalanced three-phase state, causing overheating and damage. Secondly, the disengagement time of the electromagnetic clutch for stopping is regulated by two time relays in coordination, making it difficult to control the degree of relaxation of the roving. Moreover, the electromagnetic clutch is prone to failure. Consequently, such preventive measures are rarely maintained in actual production, and the issue of roving variations remains unresolved. Presently, both new and retrofitted roving frames employ AC variable frequency technology to address this technological challenge. Tests conducted on the FA491 roving frame before and after retrofitting showed a reduction of 2-3% in CV% of roving thickness during the start-up phase and a decrease of over 90% in roving variations.
The FA491 High-Speed Roving Frame is a new type of roving frame developed in recent years in China. It utilizes industrial computers, PLCs, and VFDs to control four motors, respectively driving the spindle wings, roller, bobbin, and lifting of the dragon tendons, eliminating cone pulley speed-changing devices, molding devices, and simplifying the mechanism. It boasts high efficiency, reliability, low noise, ease of operation and maintenance. With good process adaptability and reduced yarn breaks, it achieves speeds of up to 1500 rpm, incorporating new technologies such as human-machine dialogue, parking, and automatic positioning. It represents a high-level roving frame.
The sizing machine utilizes variable frequency speed control technology to reduce the application of mechanical structures and motors. In the retrofit of the G142 series sizing machine, AC variable frequency speed control is employed, reducing the first set of mechanical continuously variable transmissions in the original design, while also eliminating one servo motor and one slow-speed motor. To meet the sizing process requirements, the speed transformation from slow to main and the elevation/deceleration are modified into continuous and stepless speed control based on the startup process speed, allowing for pressure adjustment during speed changes to achieve balanced sizing rate.
The GA308 type sizing machine adopts AC distributed drive. The upper sizing trough, lower sizing trough, and drying cylinder are driven by AC variable frequency motors, while the weaving axis and traction roller are individually driven by AC servo variable frequency motors. It employs a total of 5 VFDs, 2 servo controllers, as well as sensors for pressure, temperature, and regain. Controlled by an industrial computer and a programmable logic controller (PLC), it constitutes a distributed control system. The PLC is responsible for controlling the overall machine operation and parameters such as regain rate, temperature in the drying chamber and sizing trough, and pressure of the sizing roller. The entire machine is under the control of the industrial computer. With high control precision, stable performance, and low failure rate, this machine represents a high-quality and high-level equipment.
In the spinning process, it is essential for the electrical transmission of processing equipment in cotton spinning to be stable, ensuring smooth operation during jogging, start-up, and speed adjustment. This ensures uniform fiber tension, reducing uneven weight and CV values of the sliver. In the transmission system of cotton spinning equipment, belts and gears are primarily responsible. However, due to the starting hardness of the electric motor, phenomena such as belt slippage and gear impact inevitably occur during jogging and startup. The more gears in the mechanical transmission system, the higher the probability of gear damage. Applying AC variable frequency technology can effectively address these issues by achieving smooth startup, eliminating mechanical shock during startup, realizing stepless speed regulation, meeting production process requirements, and improving yarn quality. When applying this technology to changes in yarn count, there is no need to change gears or pulleys. Instead, changes in equipment process speed can be accomplished simply by adjusting the frequency.
Traditional old-fashioned carding machines are inevitably flawed due to factors such as technological limitations of the era, manufacturing costs, and market demand. For example, in the drive system of the A186D carding machine, the electromagnetic clutch has a high failure rate, often leading to machine downtime and occasional fires, causing certain losses in production efficiency and product quality. Significant manpower and resources are required for maintenance and upkeep. Some enterprises have abandoned the use of inertia wheel electromagnetic clutches, which leads to the occurrence of slivers and, in severe cases, broken edges and broken cotton webs during the process of converting from slow to fast speeds, affecting sliver quality. Some enterprises attempt to remedy these equipment deficiencies through improper operational methods, resulting in a large amount of waste sliver, which is equally undesirable.
The process of improving the operation status of carding machines involves various measures. For instance, the A186D carding machine is equipped with dual-speed motors, inertia wheels, and electromagnetic clutches in the mechanical transmission system to achieve smooth speed elevation and descent. In the design of A186E, A186F, and FA201 carding machines, an additional control element of star-delta conversion for the motor is introduced to further improve the elevation and descent speed slope. FA201B and FA212 carding machines adopt AC variable frequency speed control, thereby achieving arbitrary adjustment of the speed slope and the arbitrary variable function of the processing speed, providing a good example for the retrofitting of old machines.
Through the retrofitting of A186D equipment with AC variable frequency speed control technology, not only can equipment performance be improved and downtime reduced, but production efficiency and sliver quality can also be enhanced.
Variable frequency speed control technology is a crucial technology for the textile industry, especially for traditional textile equipment. As China's textile industry accelerates its internationalization process, there remains a certain gap compared to the international advanced level due to technological constraints. In order to narrow this gap, China has been continuously breaking through in the electromechanical integration of textile machinery, actively applying AC variable frequency technology to the control of textile machinery. There is a concerted effort to develop excellent textile machine inverters and AC servo motor controllers with independent intellectual property rights in China, vigorously promoting industrial automation technology.
