Development of automatic static frequency conversion power supply for viscose filament spinning machine
The development of automatic static frequency conversion power supply for viscose filament spinning machine Shenzhen Dongneng Electronics Co., Ltd. Lin Dongyu's unique hot backup function, and proposed a solution to the on-site problems in practical applications. 1Proposal of the problem In the semi-continuous spinning production of viscose filament fiber, the spinning machine is the most critical equipment in the production process. Each spinning machine is equipped with dozens of electric ingots, and the electric spindle is driven by a centrifugal tank to rotate at a high speed, and the tow entering the centrifugal tank is opened and wound into a cake having a certain twist. The speed of the ingot is generally 7500~8500r/min, and a special intermediate frequency power supply of 160V/150Hz is required. For a long time, most manufacturers have used electric-to-intermediate frequency generator sets to provide such power. Because the motor-IF frequency generator set (commonly known as dynamic frequency conversion) technology is backward, the disadvantages brought to the production are very obvious: the power frequency is fixed and difficult to adjust, the precision is poor, the stability is not good enough, and the quality of the cake is difficult to improve. The area is large and the noise is seriously exceeded. Poor reliability and standbyness do not guarantee continuity of production in the event of a unit failure. The spinning and electromechanical powers have to be re-started for more than 3 seconds, and each time they raise their heads, they will produce waste silk and waste a lot of raw materials. With the rapid development of power electronics technology, the technical level and performance of the frequency conversion device are continuously improved. The existing frequency conversion device and programmable controller (PLC) are used to form a fully automatic static frequency control system, replacing the original motor-intermediate frequency power generation. The unit has become an inevitable trend. 2 static frequency conversion system composition and performance characteristics Take a third spinning workshop of a chemical fiber plant as an example, each spinning machine has a total of 72 electric ingots (140W per ingot, rated 160kW for every 12 spinning machines) The inverter drive, the inverter output voltage (AC380V) is changed to the rated voltage of the electric spindle through the intermediate frequency transformer (380V/160V). At the same time, each inverter of 5 inverters is used as a hot backup, and is composed of programmable controller PLC. A set of fully automatic static frequency conversion system, its circuit diagram is as follows. The circuit diagram of the static variable frequency power supply system According to the working characteristics of the viscose filament spinning machine, the following problems should be considered in the composition of the entire control system. 2.1 Selection of frequency converter According to the habit of the production site, the start of the spinning electromechanical ingot usually adopts a single direct start mode; for the electric spindle with the speed up to 80009000 rpm, the reverse connection braking needs to be carried out when the viscose filament is dropped. Parking, drop wire is carried out according to several spinning machines in the zone. Therefore, the capacity of the inverter must be left with a margin. Generally, the total capacity of the ingot driven by the inverter is about 75% of the rated capacity of the inverter. It is appropriate. In addition, since the inverter output is directly connected to the IF transformer, the harmonic content and DC component of the inverter output waveform must be at a lower level. The inverter should be equipped with a power supply AC reactor and a DC side to improve the power factor reactance. Or install a filter on the output side. Of course, these conditions are very easy to implement for current general purpose inverters. 2.2 PLC control mode PLC is the control center of the static frequency conversion system, responsible for the start and stop, alarm, hot switching and interlock control of the inverter. There are two ways to control the PLC: First, a medium-sized PLC is used to control all the inverters. The advantage is that the control circuit is simple. The disadvantage is that although the PLC products have a fairly high reliability, once the PLC fails. It will bring a large area of ​​spinning machine 瘫痪, which is almost fatal for chemical fiber production. If two medium-sized PLCs are used for mutual preparation, the control circuit is very complicated; the second method is to use one for each inverter. Small PLC control, then establish correlation and interlock between each PLC; add emergency switch in each PLC control cabinet, can effectively cut off when PLC fails, and ensure that the inverter can still operate normally, guarantee the running reliability At the same time, minimize the impact of the accident. 2.3 IF transformer manufacturing The intermediate frequency transformer is proposed because the primary side of the transformer is connected to the output of the inverter, and its operating frequency (about 150 Hz) exceeds the rated frequency of the usual power transformer (50 Hz). The output voltage of the voltage type inverter has a certain amount of higher harmonics, which increases the transformer loss. At the same time, due to the error of the inverter control signal and the switching device, the positive and negative half cycles of the output phase voltage of the inverter always have slight asymmetry. Therefore, the output voltage contains a certain DC component, which puts certain requirements on the manufacture and operation of the IF transformer. If it is only manufactured according to ordinary transformers, it will cause the transformer to be in a state of saturation of the magnetic circuit very quickly, and the no-load current is very large and cannot be operated at all. In the manufacturing process of the intermediate frequency transformer, some corresponding measures need to be taken to overcome the above problems, such as reducing the design value of the core flux density, increasing the air gap in the core to reduce the adverse effect of the DC magnetic potential, and at the same time, according to the output of the inverter Features, need to increase the insulation capacity of the transformer, reduce leakage resistance, improve heat dissipation and so on. 2.4 Hot Backup Mode The hot backup mode is one of the features of the fully automatic static variable frequency power supply system. Reliable static frequency conversion power supply is the most basic guarantee for continuous and stable production of viscose spinning machine. Since each variable frequency power supply directly drives more than ten spinning machines, once a static variable frequency power supply fails, production will be made. Affected by a large area, the viscose filaments need to be re-raised after the power cord is powered off, not only for a long time, but also a large amount of waste silk, which has great economic losses. Therefore, although the current inverter devices and other components can guarantee very reliable reliability, it is still necessary to use the inverter hot backup method on the system to ensure foolproof. The hot backup mode is mainly the backup of the inverter device. According to the division of the spinning machine, several static frequency conversion devices are grouped into one group, and one frequency converter is used as a common backup machine. Both operational reliability and investment economy are considered, and 5-6 static frequency conversion devices are generally used for sharing. A frequency converter standby machine is more suitable. In some occasions, for the higher reliability, the standby units of the two sets of static frequency conversion devices are mutually standby, but the control circuit is slightly complicated. The operation of the backup static frequency conversion device is mainly divided into two modes: n static frequency conversion hosts share one standby machine, and if any one of them fails, it immediately switches to the standby machine. Host failures include: over current, over load, over voltage, short to ground, fuse open circuit, overheat, CPU abnormality and other faults. At the same time, if a static frequency conversion host inputs an abnormality on the power supply side (phase loss, trip, etc.) Etc.), the system can also automatically switch the load of the host drive to the standby machine to ensure the continuity of production. All the switching process is completed by the PLC system, mainly to control the parameters such as the switching time and switching frequency of the inverter, to ensure the corresponding chain relationship, and to give the operator a signal indication. During the commissioning and maintenance of the equipment, the host load can be manually switched to the standby machine. The manual switching mode is still performed by the PLC. In order to ensure the reliability of the system, each static frequency conversion device is equipped with an emergency switch. Once a PLC has failed, the operator can switch the static frequency conversion host to the standby device through the emergency switch. The machine is running. 3 On-site problems and countermeasures As the medium frequency power supply of viscose filament spinning machine, there are many unique features in the field use of the inverter. The parameter setting is also different from the ordinary load. The main aspects are as follows: The voltage often does not need to be as high as 160V (some new energy-saving electric spindles have lower rated voltages), so the output voltage of the inverter is often as low as 320-350VAC, and the automatic voltage adjustment function (AVR) cannot be disabled within this range. (Otherwise, the output voltage of the inverter will be proportional to the input voltage), which puts certain requirements on the selection of the inverter. As an intermediate frequency power supply, the static frequency conversion device only runs at the working point required by the electric spindle. Therefore, some functional parameters such as torque boost and DC braking, which are critical to the dynamic load operation, are not very important; The power of a single electric spindle is small, usually after the inverter runs at the working frequency, the electric spindle is started directly one by one, and the inverter is not required to drag the entire load for soft start, so the efficiency is rather low. Therefore, the acceleration time and deceleration time of the inverter can be set as short as possible, so that the inverter can reach the rated working point quickly after receiving the running command, which also meets the requirements of hot backup switching. When the static frequency conversion device performs hot backup switching, it is important to set a reasonable switching time and switching frequency. When the hot backup is switched, after the contactor on the output side of the main unit is disconnected, the electric spindle maintains a certain speed under the inertia until the output side contactor of the standby machine is closed and re-converted. Therefore, for the standby inverter, it is equivalent to starting the running motor online. To complete this online startup process without impact, and strive to keep the switching time as short as possible, several measures need to be taken: in order to ensure the safety and reliability of the switching, a certain time interval is required between the opening and closing of the two contactors. At the same time, when switching instantaneously, the voltage output by the inverter of the standby machine and the residual voltage of the electromagnet are very different in phase, which may cause electrical or mechanical failure, so sufficient decay time is required to make the residual voltage of the electromagnet after the power is turned off. Basically disappeared; however, the longer the interval between switching, the more the speed of the ingot decreases, the larger the slip, the greater the fluctuations during switching, and the impact on the production process. According to multiple field practices, this interval is usually selected. It is more suitable within 1-2 seconds. According to the functions of most general-purpose inverters, the inverter starts the motor that is rotating freely. It needs to search and detect the speed of the motor, and the output and the speed of the motor are the same, so that the motor can start smoothly without impact. (As shown) Inverter online switching diagram In order to shorten the time t1 and t2, reduce the current impact as much as possible. During the hot switching process, the frequency of the inverter running should be as close as possible to the actual speed of the ingot. This frequency value (second The frequency can be calculated by measuring the speed at which the electric spindle drops during the power-off time (1-2 seconds) and then converting it to the inverter output frequency. In fact, since the load driven by the electrospin is a cylindrical wire can, the rotation is stable and the inertia is large, so the speed of the short time drop is not much, about l-2 Hz. This allows the inverter to output one in the shortest time. The switching process is completed quickly with the same frequency as the spindle speed. Subsequently, the PLC continues to give instructions to increase the output frequency of the standby inverter to the original operating frequency. 4 use effect and conclusions viscose filament spinning machine automatic static frequency conversion power supply since its successful development in 1992, after a lot of field practice and continuous improvement, has become a type of mature industrial applications. Compared with the original motor-IF frequency generator set, it has the following advantages: stable power supply and high frequency precision, which improves the quality of viscose filament products and increases the grade rate. The operation is reliable, the design of online hot backup basically eliminates the heat stoppage time, ensures the continuity of production, greatly reduces the amount of waste wire, and significantly increases the output of the product. The maintenance of the device is small, the burning rate of the electric beaker is reduced, and the maintenance cost is greatly saved. The device has a small footprint, and the noise is greatly reduced compared with the dynamic frequency conversion unit, which greatly improves the production environment and is welcomed by workers. Based on the above advantages, most of the domestic viscose filament production plants have selected automatic static frequency conversion power products, such as Jilin Chemical Fiber Co., Ltd., Dandong Chemical Fiber Factory, Hubei Chemical Fiber Co., Yibin Chemical Fiber Factory, Weifang Julong Chemical Fiber Co., Ltd. The company, Shaoyang Chemical Fiber Factory and Jiujiang Chemical Fiber Factory have not only greatly improved the overall technical level of the production equipment, but also achieved significant economic benefits.
Flexible 4 and 8 Pvc Foam Sheet For Kitchen Cabinets for Kitchen Cabinets Pvc Foam Board is also called the chevron board and Andy board, with polyvinyl chloride ( PVC ) as the main raw material, add a variety of additives.Surface: printing color, can be coated or made of a variety of colors, with flame retardant, moisture, acid and alkali, long life, high strength, non-toxic, anti-aging ability, can be hot forming and so on .Environmental protection: Flexible 4*8 Pvc Foam Sheet for Kitchen Cabinets to save valuable forest resources, save energy, protect the ecological environment and promote the sustainable development of human society is of far-reaching significance.
Flexible 4 and 8 PVC Foam Sheet for Kitchen Cabinets for Kitchen Cabinets Key Features :
Flexible 4 and 8 PVC Foam Sheet for Kitchen Cabinets Applications:
PVC Foam Sheet Pvc Foam Sheet,Flexible Pvc Foam Sheet,Pvc Foam Sheet For Kitchen Cabinets,Pvc Foam Board SHENZHEN XIONGYIHUA PLASTIC INSULATION LTD , https://www.xyhplastic.com