What are the applications of frequency converters in roving frames?

1. Introduction

In the spinning process, the roving process plays a pivotal role. With the development of power electronics technology, PLC control, frequency conversion speed regulation, mechatronics and other technologies are used to replace the traditional mechanical structure, and the new type of suspended spindle roving frame gradually replaces the support spindle roving frame, which improves the reliability of the whole spinning machine, improves the spinning quality and automatic operation. Especially in recent years, the wide application of frequency conversion speed regulation technology in roving frames has given roving frames a broader development prospect.

2. Analysis of the application of frequency conversion technology on roving frames

According to the requirements of the spinning process, the roving machine draws the cotton strips through the rollers, and then the yarn is pulled out by the front roller for twisting. Then, according to the requirements of winding and forming, the yarn is wound on the bobbin. Since the yarn output speed of the front roller is constant, and the winding speed decreases in inverse proportion with the increase of the winding diameter, the traditional roving machine adopts a mechanical cone wheel speed change mechanism, and the belt moves on the upper and lower cone wheels to change the winding and lifting speed to complete the roving winding and forming. One of the factors that affect the quality of the yarn in the roving production process is the details caused by starting, stopping and jogging.

1. Single motor driven roving frame

The main drive of the roving frame is driven by an AC asynchronous motor. In order to solve the problems of roving breakage caused by too fast speed increase of the motor when starting and uneven roving when stopping, the traditional solution is to install reactors, time relays and electromagnetic clutches, collectively referred to as "anti-detail devices". In addition, when the speed of the whole machine needs to be changed for spinning different varieties, the speed change is achieved by manually replacing the pulley.

The application of frequency conversion technology can effectively solve the problem of smooth start-up, eliminate the impact force during mechanical start-up, achieve stepless speed regulation, meet production process requirements, and improve yarn quality. When this technology is applied to the situation of spinning different varieties, there is no need to change the teeth or pulleys. The change of the equipment process speed can be completed by frequency conversion setting, but the cone wheel speed change mechanism is still retained.

At present, AC frequency conversion technology is used in new roving frames and the transformation of old machines. This process problem has been solved. After testing the yarn quality before and after the transformation of the FA413 roving frame, the CV% of the roving in the starting section decreased by 2-3%, and the coarse and fine details of the roving decreased by more than 90%.

2. Multi-motor driven roving frame

Since the mechanical bevel gear speed change mechanism has poor transmission speed stability and is difficult to operate, it is easy to cause unstable roving quality. Therefore, many manufacturers have launched new roving machines with multi-motor transmission, which have eliminated the bevel gear speed change mechanism, forming mechanism, differential mechanism, swing mechanism and reversing mechanism, as well as the twist, lifting, winding, tension, forming angle and other gear changes.

Four motors are used to drive the drafting rollers (to generate the drafting multiple), the flyer (to wind the roving onto the bobbin), the bobbin (to generate twist in the roving) and the lifting of the dragon tendon (to complete the winding shape). The use of four motors for transmission not only simplifies the mechanical structure and eliminates the gears of the above-mentioned mechanisms, but also reduces noise, increases the speed, reduces the breakage of roving, increases the output of a single machine (the speed of the main machine is increased by more than 30%), ensures the stability of the roving quality, and makes the process change simple and fast.

However, the single-motor driven roving frames currently produced account for a large proportion, because of their low price. Multi-motor driven roving frames have high speed and good performance, but due to their high price, their sales volume only accounts for about 10%.

3. KE300A inverter control solution for suspended spindle roving frame

1. Features of the Micron KE300A inverter

The Mycano KE300A inverter has achieved high efficiency and low failure rate in the on-site suspended spindle roving frame, and has been unanimously recognized by customers. The advantages of the solution are summarized as follows:

(1) Smooth start and stop: Slow acceleration, using the S-curve acceleration and deceleration function, the motor starts and stops gently and smoothly. Reduce the impact wear and breakdown of the machine and protect the mechanical equipment.

(2) Convenient speed regulation: The output frequency (speed) of the inverter is adjusted by an external potentiometer, and there is no need to replace the speed wheel of the machine. Different spinning speeds can be set according to different spinning processes, that is, the spinning speed can be set higher for small yarns and appropriately lower for large yarns, so as to give full play to the potential maximum production capacity of the roving machine.

(3) It has the function of spindle wing positioning and parking.

(4) When changing the spinning variety, there is no need to replace the pulley, just set the required speed through the inverter.

(5) The starting current is small, which reduces the capacity of the power supply equipment and has a significant power saving effect.

2. System control scheme

The main circuit wiring is very simple. Connect the three-phase power supply to the inverter input R, S, T terminals, and connect the inverter output U, V, W to the three-phase terminals of the corresponding motor. Pay attention to the terminal markings when wiring to avoid misconnection or reverse connection. Details are shown in the figure below:

The above diagrams only list the commonly used control wiring configurations. If you need to implement complex functions, please refer to the manual to modify the relevant wiring circuits and terminal function definitions. Since KE300A is a standard model, most parameters can be set according to factory parameters. When using it, users do not need to make too many complex settings, but only need to make simple parameter modifications according to the actual use site.

4. Effect

The application of Micno KE300A inverter in roving frames actually solves the problems in the roving production process. And the use of inverter control makes the system control simpler, and the control system has multiple protections, making the system safer and more reliable. Ordinary roving frames such as FA421, FA423, TJFA458, etc. all use variable frequency speed regulation technology.

V. Conclusion

The application of variable frequency speed regulation technology in roving frames is necessary, and it is also feasible to promote and apply it to traditional roving frame equipment. With the development of microelectronics technology and power electronics technology, the development of variable frequency speed regulation technology has also made great strides. Today, the adoption of variable frequency speed regulation technology has directly promoted the rapid development of the mechanical structure of roving frames, laying a solid foundation for the high speed, high quality and high intelligence of roving frames. It can be said that without the development of variable frequency speed regulation technology, there would be no high-quality roving frames today. The increasingly high level of mechatronics of roving frames will be the future development direction.