Mar 30, 2021
The production improvement plan for the application of frequency converter to the old carpet machine
Many of the existing spinning machines of some small textile factories in my country were imported from abroad in the 1980s and 1990s. Most of these devices are relatively outdated, and the level of automation is worrying. In the new equipment produced now, mechatronics is basically realized, the centralized control system, production efficiency and quality have been greatly improved, but the equipment cost is quite expensive. Now the majority of industrial control personnel pay great attention to the automation and frequency conversion transformation of textile machinery.
As a high-tech product, the inverter, which has the advantages of energy saving and environmental protection (the two directions of world economic development), has attracted more and more attention, and has gradually replaced DC speed regulation, and has a pivotal position in the transmission system. . Inverter is mainly recognized as the most ideal and promising speed regulation method at home and abroad for its excellent speed regulation and starting and braking performance, high efficiency and significant power saving effect, and wide application fields. With the continuous improvement of the technical level of textile machinery mechatronics in recent years, AC frequency conversion speed regulation has become a trend. Almost without exception, AC asynchronous motor variable frequency speed regulation devices are used in most newly developed textile machinery products.
Second, the working principle of the carpet machine frequency conversion transformation
Taking the carpet machine produced in the United States in the 1980s as an example, the entire electrical control structure is relatively simple, the level of automation is low, and the labor intensity of workers is high. After referring to the working principle and technological requirements of modern imported textile machines. We have carried out a series of technical transformations on this equipment.
Choose a frequency converter SAFESAVE 200g series 15KW frequency converter (with braking resistor) to synchronously control two 5.5KW spindle motors, assisted by Omron photoelectric switch, Schmersal safety cable switch, German P+K proximity switch, etc. Components, control the start, stop, alarm, full yarn, doffing, etc. of the whole machine.
1. The working process of frequency converter speed regulation
The spinning machine needs a slow start, slow stop, yarn break, and full yarn precise stop process. The whole process of frequency converter speed regulation is as follows:
2. Realization of start-up and shutdown process
The motor needs to prompt for 2s before running, and a 60 decibel buzzer is used to buzz for 2s before starting to remind the operator to leave the needle work area with their hands. In order to overcome the shortcomings of weak and unsmooth starting at startup, the starting frequency is set to 6hz, and the starting torque is appropriately increased. At the same time, another function of the inverter, namely the S curve, is added to the starting process, so that it is slow. The starting function also has a relatively smooth starting process, which makes people feel the speed change during the low-speed ascent process. This solves the problem that the motor often burns out in direct starting, and prevents the occurrence of roving details and broken ends.
The S-curve deceleration process is also used when the yarn is broken, the full yarn is stopped or the safety protection is stopped. Another special requirement for the roving frame to stop is the positioning of the flyer. The flyer stops at the same position every time the machine decelerates and stops, and the needle exits the cloth layer 3mm away from the cloth surface (with an accuracy of 1%) for easy operation. Operation. We can use the programmable input and output terminals of the inverter and PLC programming to realize the key points of this technical requirement. The specific process is as follows. When the inverter decelerates and stops to the set frequency of 6hz, it uses a programmable relay to output a signal to the PLC. After the PLC judges the signal, it outputs a jog signal to the inverter and keeps running at a low speed of 6hz for a certain period of time. At this time, the photoelectric proximity switch starts to work and detects the position detection point installed on the flyer wheel. The detection output switch signal is PLC. The PLC counts once when the wheel rotates once. After the count is completed twice, the PLC outputs a signal to the inverter to turn off the output. , At the same time the electromagnetic clutch is activated.
3. Frequency conversion jog realization
Frequent jog is another feature of the carpet machine. As long as the jog button is pressed, the carpet machine will keep running at a certain frequency. This low-speed operation is for the convenience of operation, testing, and maintenance. It requires low-speed operation and can be parked at any position. But the inverter cannot work under 6hz for a long time, and continuous and frequent movement will cause over-current protection. We add a judgment program to the PLC, which means that the continuous jog only responds once within a certain period of time. When inching, we do not require an accurate position to stop, so we add another judgment program to the PLC programming to judge whether it is inching or normal operation. If it is inching, it will not respond to the prompt sound, the proximity switch will not work, and the electromagnetic clutch will continue to work. PLC can fully realize these functions because of its rich programmable instructions. Dien Electric Inverter also has complete programmable external control terminal input and output, which can be easily connected with PLC. The wiring diagram of the external control terminal of the inverter is as follows:
4. Emergency stop system
In this equipment transformation, we have added many functions: install a safety cable switch on the front and back of the device, and workers can easily pull the cable in an emergency to stop the motor immediately. We chose the fiber optic photoelectric sensor to detect the disconnection. After the disconnection, the end of the thread drifts through the photoelectric detection area, and the photoelectric switch acts to output a signal to the PLC. The PLC issued a warning and stopped.
Because the flyer rotation has a certain inertia, and the equipment is constantly in the process of rapid stop during operation, the inverter adds a braking resistor to achieve energy consumption braking to ensure that the inverter will not be protected against overvoltage.
3. Effect analysis
After the carpet machine has been transformed into operation by the inverter equipment, the work is stable and reliable, the operation is convenient, and significant economic benefits have been achieved. After adopting frequency conversion speed regulation, the motor speed can be adjusted according to needs to improve production efficiency. The motor runs steadily, the quality of the carpet surface is obviously improved, and after parking can be realized at an accurate position, there are no more signs of shutdown on the woven carpet. The safety protection system is perfect, and the labor intensity of workers is greatly reduced.
Four, concluding remarks
The above content analyzes how the frequency converter realizes the frequency conversion speed regulation and automation transformation in the imported carpet textile machinery, and describes the carpet machine using the frequency converter to control the positioning, slow start, and variable speed process during operation. It meets the requirements of the textile technology, greatly improves the textile quality and reduces the labor intensity of the operators. In this way, with the continuous improvement of the automation level, the production equipment is more and more advanced, and the product quality is continuously improved. Only good quality products can be invincible in the market competition.