Application of the hottest frequency converter in

2022-08-08
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Application of frequency converter in the transformation of sheet fed lithographic printing machine

introduction

at present, new electrical control technology has been widely used in domestic sheet fed lithographic printing machines, such as PLC, touch screen, frequency converter, etc. Compared with the old type of equipment a few years ago, these new sheet fed lithographic printing machines have the advantages of high reliability, energy saving and high efficiency, and perfect functions. However, in many printing enterprises at present, the old type of sheet fed lithographic printing machines still have a considerable number. If they are transformed and PLC and touch screen are all used, a large number of lines need to be changed, which is almost equivalent to remaking the electrical control system. If only the main drive part of the sheet fed lithography press is transformed with frequency converter, the line change is small and the workload is small. It not only retains the simple and practical characteristics of the original relay contact control, but also includes domestic automobile manufacturers such as Great Wall Motors, Chang'an Automobile (Weibo), Chery Automobile, SAIC automobile group, etc. which have also been pocketed by it, giving full play to the advantages of reliable and energy-saving frequency converters, and the cost performance of the transformation is high. The following is about the application of frequency converter in the transformation of domestic single and double color sheet fed lithography press

2 process characteristics of printing machine operation control

in order to make the inverter driven variable-frequency motor can be well applied to the printing machine and meet the requirements of production process, we must first understand the process characteristics of printing machine operation control, what requirements it puts forward for the function of the inverter, then choose what type of inverter, and how to concretely transform and connect the original circuit

the operation of the sheet fed lithographic press is driven by the motor through belt drive, gear drive and chain drive. The action of each drum, tooth row and mechanism is coordinated by mechanical connection, so the motor that controls the main drive controls the operation state of the whole machine. During mechanical adjustment, inspection, installation and disassembly of PS version and blanket, and cleaning of the machine, it is necessary to control the forward and reverse operation of the machine by manual car counting. The speed of about 4r/min is more appropriate. During the printing pause, in order to ensure that the PS version is not damaged and the ink is not dry, the machine should be operated at the same speed for a long time. When the machine starts formal printing production, it has an initial speed of about 3000 rpm. When the paper feeder starts to feed paper, it can accelerate to make the machine produce at a higher speed, generally 6000 ~ 8000 rpm. In order to adapt to different production speed requirements, the high speed can be adjusted through a speed regulating potentiometer, and the actual value of the speed can be indicated by the speedometer. There are two situations when the printing speed drops from the high speed of printing to the initial printing speed. One is to slow down the manual button, the other is to detect paper faults in the printing process, such as skew sheet, no paper, double sheet, etc., which makes the printing machine automatically slow down, and all parts make coordinated actions accordingly, such as pressure off, water off, ink off, paper feeding stop, etc. At the end of production, press the stop button, and the machine will stop smoothly in a free stop mode accordingly. In addition, in order to ensure personal safety, safety protection switches or emergency stop buttons are installed in the dangerous parts of the printing machine. As long as these switches act, the machine must stop immediately and the whole machine must be braked urgently no matter what state it is in

3 requirements for the functions of the frequency converter

(1) there should be three-stage speed control and direction control functions to meet the requirements of positive and negative car counting, positive and low speed, initial printing speed and high speed

(2) the simple experimental setting of high-speed application is more reasonable; For research users who care about the details of the experiment, the speed value of operation is variable. It is best to adjust the speed steplessly by manually adjusting the potentiometer to meet the requirements of different processes

(3) there should be speed indication for machine operation, so that the operator can know the current operation state

(4) the acceleration and deceleration process of the machine should be stable and the speed should be appropriate, so that the speed change is timely and smooth without impact, and the whole machine should also be stopped in case of failure of the frequency converter itself

4 parameter selection of frequency converter

according to these requirements, the vast majority of frequency converters can meet. For the occasions used, choose general-purpose frequency converters. The selection of voltage capacity depends on the connected power supply and the motor used by the original machine. Here, we use 400V inverter, 5.5kW inverter for monochrome machine and 11kw inverter for two-color machine. There are many kinds of inverters in the market. Generally, we choose mainstream products with good quality, such as Mitsubishi A540 series, Yaskawa G5, Delta, etc. Although these products have high prices, their quality is guaranteed. For the electrical core components of a printing machine, it is better to invest a large amount at one time to avoid the trouble caused by frequent failures in the future. Of course, if you have a grasp of the quality and performance indicators of other brands of frequency converters according to the fault performance of the equipment, you can also choose, which can save some. After having the hardware of the frequency converter, its internal parameters should be set. In terms of speed parameters, the inching frequency can be set to 2.5hz, the initial printing speed is 25Hz, and the high speed is about 60Hz. Taking Mitsubishi inverter A540 series 400V and 11kw products as an example, the following describes its specific wiring and transformation connection with the old printing machine. The wiring of the two is shown in the attached figure, and the relevant precautions are as follows

attached drawing frequency converter connection diagram (KM1, km2, KM3, KA1, KA3 are the element numbers of the original drawing)

attached table comparison table of main motor energy consumption before and after the transformation

(1) the main drive device of the original printing machine is an electromagnetic speed regulation (slip) motor, low-speed motor, clutch, brake and other mechanisms, which are removed and not used, and replaced by a special motor for frequency conversion and speed regulation produced by Shanghai Tongtai motor company, The 11kw/380v machine is equipped with three-phase power-off brake and cooling fan. The mounting base of the original motor can be used, and the pulley of the original motor can also be removed and installed on the new motor shaft

(2) since the original main motor c= (c1+c2+c3+c4)/4 and the low-speed motor have been removed, the wiring of the main contacts of contactors KM1, km2 and KM3 in the distribution box can be removed. Use the remaining available contacts as the switch contacts of the frequency converter control signal according to the new line. Because the contact of the original relay may have a long service life and poor contact, it is best to replace it. The forward input terminal STF, the reverse input terminal STR, the medium speed terminal RM, the low speed terminal RL, the reset terminal Mrs, and the common terminal SD wiring of the frequency converter need to combine the relevant contacts in series and in parallel to meet the three-stage speed regulation requirements

(3) the original electromagnetic governor zlk-11 is also removed. It is just possible to use its installation position to make a suitable speed regulation display box. Use a 1K Ω/zw wound potentiometer to connect to the analog signal input port - 10e, 2.5, and use a full-scale 10V DC voltmeter to connect

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