This article gives a brief introduction to the design and operation of the electronic control system for finished-product flying shears. The main design specifications of the double-spaced flying shears are as follows: bar line speed V1=4~12m/s; multiple-length cut length: 54m (fixed length 9m); cutting accuracy: *600mm; start-stop period: 2.5 s; tail steel length range: (20m, 60m) finished product double cut fly shears is the key equipment to improve the yield rate and length rate. There have been no failures since the two flying shears were formally put into operation. This shows that the hardware and software design is successful, and it has taken a step toward localization of high-speed flying shear equipment.
2 Hardware Setup Overview The flying shears are set as follows: The drive motor is a domestic low inertia DC motor, model number is ZFQZ*315*32 rated capacity, voltage and speed are 200kW400V600rpm in sequence. The flying shear machinery is manufactured by a domestic high-speed gear machine factory without The reduction gearbox is directly connected to the output shaft of the DC motor.
Velocity and position feedback share a single encoder, model number TRD-1000; the flying shear main drive adopts all-digital DC device, model: 6RA7087; PLC adopts S7*3(1) series of products, totaling only 4 modules: CPU (Model: CPU315*2DP), high speed count input module (FM350-2), digital input module and power supply module.
Communication is via the MPI bus and the CBP module, respectively.
Each of the two flying shears electronically occupies a dedicated panel, which houses the 6RA70 host and PLC and shares a switchgear. Three cabinets account for a total of three steel rolling process requirements for the finished product flying shears electronic control system 1 from the start to the flying shears after cutting for some time, the electronic control system works in a closed loop speed, cut in the steady speed, shear Small dynamic speed drop; 2 After the electronic control system is turned into the closed loop of the shear edge angle position, it can return to zero position quickly and accurately without zero oscillation; 3 It has a perfect detection system. Through the hot metal detector to get the bar, to go through the mill encoder to get the bar travel speed and the shear angle of the flying shear shear, and to calculate the actual length of the bar; 4 communication with the host computer, receive Order multiples, bar diameter and other directive information, and with the host computer to exchange the shears machine and other mill rolling mill fault information; 5 has a perfect accident warning and protection system.
4 Optimized Shearing Introduction A piece of bar material that is cut is called tail steel. The head that is not formed by shearing is called the head piece. Although it is possible to arrange the rolling schedule and try to control the length of the tail steel, it is still a random variable with a large variance.
The task of optimizing the shear is to make the length of the tail steel moderate to ensure that no empty cuts occur.
If the tail steel is too long, the cold bed will not survive; if it is too short (including air-cut), there are the following problems: 1 Because the acceleration force and resistance of the bar on the roller path to the cold bed are related to its length, the short steel tends to go slowly. If the tail steel is chased after the head, it will cause the HMD3 to report the arrival of the head, resulting in the result that the entire bar is not sheared straight into the cooling bed; 2 if the bar end has left the exit mill after shearing, 2 The speed of travel will be uncertain, and the precision of cut length will be difficult to ensure. 3 Because the rapidity of the cooling bed operation is limited, there must be a certain time interval between the two actions of the cold bed. If the tail steel is too short, the speed of the cold bed will be dialed. Can not keep up with the speed of steel; 4 flying cut air cutting is not only a waste of resources, but also may cut to the next head of the bar, resulting in difficult to "short head."
By predicting the length of the finished steel product, PLC made a decision on how many knives will be cut, and whether or not it is necessary to judge the last one by “debit* (by taking 1~2 lengths of cut lengths)†in order to optimize the cutting.
The premise of optimizing the shear is to predict the length Ls.Ls of the finished bar of the entire billet as Ls=EV. Among them, TX is the time of billet in the field of view of HMD2, V, is the average value of M. Ls = TV, derivation: set the total volume of the rack exit steel to W steel cross-sectional area of ​​S, then Ls = W / S,.
Because the rolling does not change the total volume of steel, if HMD2 is installed in Gaoyue Nong, Shi Qingyuan et al. Start-stop cut-head shears using PLC control design and commissioning Electrical Drive Automation, 1999, (3). (Continued on page 60) Calculating short-circuit current values ​​at different short-circuit points does not require blind pursuit of high-short-circuit breaking indicators. Molded case circuit breakers currently available on the market include Economic Type (C), Basic Type (N), Standard Type (S), and High Breaking Capacity Type (H). Their short-circuit breaking currents are from small to large in order to suit different line protection needs. In the same case current, the higher the short-circuit breaking capacity, the higher the price. The price of CCM1-400H MCCB (80V, 65kA) is 1.2 times that of CCM1*400S (380V, 35kA), and the price gap of imported products is even greater. It can be seen that saving the investment in circuit breakers when designing the system should be considered as a problem to be considered by the designer when selecting the type.
The distribution system design also requires that all levels of circuit breaker operating characteristics should be able to coordinate with each other, according to selective action, that is, when a fault occurs, the breakers close to the fault point should be disconnected, and the upper and upper levels rely on the power supply The side direction is up.) The circuit breaker does not operate, limiting the power-off range to a minimum.
There are two kinds of rated breaking capacity of circuit breakers, that is rated rated short-circuit breaking capacity I* (the circuit breaker carries out the test of this item, its test procedure is OtCO, O is breaking, CO means immediately after being connected, t is the rest time, (usually 3min) and rated running short-circuit breaking capacity Is (test procedure is OtCOtCO) IEC947*2 and GB14048.2 standard both stipulate that Is can be 25% of I* 50% 75% and iro%. In general, Is is less than/ (Depending on the type of installation for the circuit breaker, universal breakers (CCW1 such as DW17, AH, etc.) are usually used for power supply (V). It is focused on /s. and used for power distribution (Class I). ) Plastic-cased circuit breakers (such as dishes 1,10,1,0220, etc.) weigh heavily on the requirements of /1.4 undervoltage release if the line voltage is reduced to 70% of the rated voltage, this voltage is called The breakdown voltage will make the motor unable to start, the dark light of the lighting equipment, and the insufficient heat of the resistance furnace, while the motor in operation, when the working voltage drops to the critical voltage of about 50%, the motor will stall and the motor current Rise sharply up to 6 , the time is slightly longer motor will In order to avoid the above situation, the undervoltage release of the circuit breaker should be selected.Operation of Undervoltage Release (P.39 of the previous page) Rolling Production Process and Equipment Beijing: Metallurgical Industry Press, 1999.: Industry Tsinghua University's Department of Automatic Control, once worked at Wuhan University of Science and Technology, is currently working at Tianjin Pioneer Electromechanical Co., Ltd. It is mainly engaged in control theory teaching, electrical transmission, steel rolling automation, and motor soft start work.
The voltage is set at 70% of the way and important branches, and the instantaneous action is often used for the general branch. In regions with poor power supply quality, voltage fluctuations are large, and often undervoltage trip units are not suitable for use when operating near the upper limit voltage of the undervoltage release.
5Using quadrupole disconnection The current distribution in the city promotes the TN*S grounding system (three-phase five-wire). Under the premise of ensuring that the PE line is not disconnected, it is required to connect three phase lines with the neutral line (N line). On the circuit breaker, its purpose and reasons are: 1 If the N line is not connected and disconnected with the phase line, the zero potential rise of one system may be transmitted to another system, which will endanger the safety of the maintenance personnel. 2 TNTT systems with large zero-sequence currents. When a power line or tie line is laid with a shield or metal pipe, if the switchgear used to switch or connect incoming power is not connected at the same time, the N line will be connected together with other phase lines or Disconnected, or several loops of PE lines are connected in parallel by repeated grounding, then the neutral line will be shunted, causing the metal pipe or shield to generate heat due to the internal synthetic magnetic potential is not zero, resulting in accidents and large internal losses.
In view of the above-mentioned reasons, especially the first one, four-pole circuit breakers can be used for the TT and TN systems. The four-pole circuit breakers are provided for electrical isolation and should be located at the power inlet and one for two power supply switching locations. .
In the selection and installation of circuit breakers, attention should be paid to the synchronism between the N pole and other poles (this is not in contradiction with the design of the N pole of some circuit breakers after the first combination). The most dangerous is the N pole action, poor contact of the static contact or after closing, forming the actual N line break, will make other three phases and the change of the phase voltage after disconnection increase or decrease, resulting in some equipment Burned, so the choice of four-pole circuit breakers should be careful.
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