Five 150Nm3 air compressors were added to the air compressor station of the cold rolling mill. Each air compressor was equipped with a separate small complete controller to control and monitor the operating parameters of the air compressor. In order to realize the remote monitoring of the air compressor, each air compressor controller communicates with the overall control system of the unit, and the communication connection is as shown. After the equipment is put into operation, lightning strikes occurred in the air compressor station several times, and the welding work in the vicinity area, even the adjacent air compressor started, causing the air compressor controller to crash, or even the damage, causing the normal supply of compressed air to the production unit. Great impact. To this end, the focus on the air compressor controller is subject to electromagnetic interference, causing crashes or even damage, analyze the corresponding causes, and propose corresponding improvement measures. 1 Electromagnetic interference mechanism and suppression measures 1.1 Electromagnetic interference mechanism The electromagnetic interference (EMI) mode is divided into differential mode interference and common mode interference. The former is mainly caused by the interference voltage formed by the coupling of the space electromagnetic field between the signals and the conversion by the asymmetric circuit. If the loop circuit of the air compressor station control system is in an external alternating magnetic field, a disturbance voltage and a useful signal voltage u. are induced in series in the loop, and a corresponding interference current is generated in the loop. The differential mode interference voltage is generated in the receiving device. The latter is mainly due to the ground potential difference and the superposition of the same direction voltage induced by the space electromagnetic radiation on the signal line, as shown, if the ground potential is raised, at the signal line The common mode interference voltage u occurs between the ground and the ground. Although the coal mine electromechanical interference current generated by u=4a = is insufficient to form the interference voltage in series with the useful signal u, when it is large enough, it may cause breakdown of the circuit or equipment. Serious damage. If the frequency of the wanted signal and the interfering signal increases, due to the stray capacitance between the wire and the ground, the common mode voltage drives the same current in the two signal lines and the impedance of the two signal lines on the current loop is completely When the same, =, there is no interference voltage at both ends of the receiving device. However, when the impedance of the two signal lines is different, the differential mode interference voltage will also appear at both ends of the receiving device, which results in the increase of the interference signal frequency and the conversion of the common mode interference into differential mode interference. 1.2 Inhibition measures of electromagnetic interference 1.2.1 Inhibition measures of resistive coupling Resistive coupling is mainly caused by the resistance coupling between the working current loop and the working current loop and the ground current loop due to the common resistance between the lines. There are two cases of resistive coupling between. The former is mainly the impedance of the common circuit of the two circuits. When the signal frequency is not too high, the impedance of the wire is mainly composed of the resistance R and the inductance L, but the current through the circuit generates an interference voltage on the common wire, and is connected in series with another voltage. Become a differential mode interference signal. The main measures to reduce this interference are: separating the two working current loops, eliminating or reducing the common impedance, eliminating or reducing the interference voltage; installing a capacitor of sufficient capacity at the input of the working unit, when a transient interference voltage occurs. When the capacitor absorbs its energy, the interference voltage is reduced. The coupling between the working current loop and the ground current loop is mainly due to the grounding of the outer casing of the transmitting device and the receiving device, the transmitting device casing, the communication line, the receiving device casing, and a ground loop formed with the earth. When there is a potential difference between the transmitting device and the receiving device, or an electromotive force induced by an external magnetic field in the ground loop, a differential mode interference voltage is generated in the grounding current loop. Measures to reduce the coupling interference between the working current loop and the ground current loop are: single-point grounding, that is, only one point of the transmitting device and the receiving device is grounded, or an isolation transformer is used between the communication lines to cut off the grounding current loop. In addition, optical couplers and optical fibers can be used to cut off the ground current loop, thereby effectively reducing electromagnetic interference. 1.2.2 Capacitive coupling suppression Capacitive coupling is mainly derived from the interaction of electric fields between lines, that is, electromagnetic interference caused by the coupling of "stray capacitance" between conductors. The measures to reduce the interference between the wires through capacitive coupling are mainly: by increasing the distance between the interference wires and the interfered wires, shortening the parallel segments of the two wires, reducing the stray capacitance between the two wires; or using shielding technology to shield Layer grounding to reduce electromagnetic interference caused by capacitive coupling. 1.2.3 Inductive coupling suppression measures are mainly caused by the interaction of magnetic fields between the lines, electromagnetic coupling mainly occurs between two or more circuits with current. When a current is passed through a circuit, a magnetic field is generated and an interference voltage is generated in the circuit nearby. Measures to reduce inductive coupling interference include: shortening the length of parallel wires between the two circuits; increasing the distance between the circuits; placing the two circuits orthogonally; tightening the return wires of the circuit to reduce the magnetic flux area; Measures such as shielding the loop to reduce or eliminate the differential mode interference voltage generated by the inductive coupling. 1.2.4 Radiation coupling suppression measures refer to the interference generated by the interference source propagating through space to sensitive equipment, mainly the combination of electric field and magnetic field. Electromagnetic radiation interference in the near field is caused by interference caused by electrostatic induction and electromagnetic induction, and far field is interference caused by electromagnetic waves. Any current-carrying conductor generates an induced electromagnetic field and radiates a predetermined intensity of electromagnetic waves, which is equivalent to a section of the emission line. In the electromagnetic field, any conductor is equivalent to a receiving antenna, which generates a certain electromotive force. Measures to reduce ray coupling include: reducing the length and area of ​​the loop; twisting the back and forth wires; shielding, etc. 2 Analysis and countermeasures for electromagnetic interference of air compressor station control system 2.1 Electromagnetic interference source and existing problems of air compressor station control system 2.1.1 Electromagnetic interference source Coal mine electromechanical investigation and confirmation confirmed the interference source of electromagnetic interference of air compressor station controller Mainly for electrostatic induction lightning, electromagnetic induction lightning, high voltage cable start surge current, argon arc welding radiation interference. The interference path is: also from the electrostatic induction lightning and the capacitive coupling interference caused by the large starting surge current of the high voltage cable when starting from the high voltage motor; the impulse current from the lightning electromagnetic pulse, the starting current of the high voltage motor, and the operation of the argon arc welding machine Radiative coupling interference. 2.1.2 Problems at the site 1) During the actual construction process, an intermediate terminal box, 5 controller communication cables, and cable trays were inserted into the intermediate terminal box, and then the total control system was connected through the root communication line. , forming a tree connection as shown, resulting in a decrease in anti-interference ability. 5 controller connection methods 2) The screen connection of each communication cable is not continuous. As shown, between the air compressor field controller A and the electric room control cabinet controller B, the outer shield mesh end of the communication cable is disconnected in the field junction box, and the air compressor controller A signal floats when shielding After the line receives the interference signal, the common mode voltage VQS of the transmitting and receiving terminals will increase, causing the controller to crash or even be damaged. Through the shielded communication line of the high-altitude cable tray, from the controller A to the communication intermediate junction box, one end of the shielding layer is suspended in the middle junction box, and the other end is connected with the signal ground of the controller. The ground is still in a floating state for shielding of the shielding. The layer can neither act as a shielding function, but also resembles an antenna to receive radiation interference from lightning current, high voltage cable impulse current when the motor starts, and argon arc welding. As shown, the interference voltage generated by the shielded line causes the common mode voltage Vs of the RS485 ground line and the receiving and transmitting ends to rise. When the common mode is too high, it will inevitably cause a false signal and even destroy the RS485 interface and other components. Shielded line interference principle) There is a problem in the laying of high-voltage cable, power cable and communication cable. During the construction process, the same wall is covered with 3kV high-voltage cable tray, 380V/220VAC cable tray and communication cable tray, of which high-voltage cable At the top, the communication cable is placed at the lowest position. During the start and stop of the high-voltage motor, the communication cable runs through the powerful magnetic field formed by the high-voltage cable and the ground. At the same time, the high-voltage cable descends from each cable bridge to each air compressor. The distance from the communication cable is only 10cm, and the distance is too close, which increases the capacitive coupling interference and the inductive coupling interference intensity. 2.2 Technical measures to suppress electromagnetic interference of control system 2.2.1 Reduce the interference intensity of interference source 1) Increase the full-closed cover plate of high-voltage cable tray to reduce the radiation intensity of external electromagnetic interference of high-voltage cable. 2) Add a lightning protection belt at the top of the plant to reduce the impact of lightning interference on the controller and communication cable. 3) The welding machine is away from the plant operation and reduces the electromagnetic interference to the control system during the welding machine operation. 2.2.2 Disconnecting the interference path 1) Lay the high-voltage cable and the communication cable in parallel to lay the spacing, and the communication cable is laid along the ground; reduce the length of the high-voltage cable and the communication cable to be laid in parallel, and the communication cable is laid along the ground, perpendicular to the vertically-radiated high-voltage cable. The specific measures are that the communication cable is laid along the outer wall, enters the controller through the wall, pulls the high-voltage cable and the communication cable parallel to lay the spacing, and forms a radiation pattern perpendicular to the high-voltage cable before entering the controller to reduce electromagnetic interference. 2) Communication cable wears galvanized steel pipe along the ground, galvanized steel pipe, multi-point grounding, double-layer shielding, communication line end shielding, reducing electromagnetic interference and static induction interference, see. Communication cable galvanized steel pipe diagram Coal mine electromechanical hydraulic support structural parts welding process research Fan Zhixin (Datong Coal Mine Group Electromechanical Equipment Company Central Machine Factory, Datong, Shanxi 037001) Selection of process parameters, selection of welded joints, welding stress control, welding process Process measures such as prevention of stress concentration, control and prevention of welding residual deformation. Practice has shown that the use of these technological measures can ensure the welding quality of the structural members of the bracket and achieve good results. INTRODUCTION In recent years, with the continuous improvement of the comprehensive mechanized coal mining level, the hydraulic support design is also lighter in weight, high in material strength, and pressure-bearing 2.2.3 to improve the anti-jamming performance of the controller. The RS485 communication line uses a "hand-hand" connection. Ways like. Set the terminating resistor to solve the non-terminal resistance of the original tree connection, causing communication interference and noise reflection problems. At the same time, the communication cable is connected to realize the equipotential connection between each controller and the electric room control cabinet. 5 controllers "handshaking" connection mode 3 Conclusion Through the analysis of the electromagnetic interference of the air compressor station control system, the effective electromagnetic compatibility design is proposed to develop the reasonable connection height of the communication cable. The thin plate thickness will inevitably cause the problem of increased welding deformation; the high strength will also result in the increase of welding residual stress. Therefore, the guarantee of welding quality and the control of welding deformation become the key to the quality of hydraulic bracket manufacturing. The author participates in the hydraulic bracket knot-type, the effective connection of the shielded cable, and the extension of the distance between the high-voltage cable and the communication cable can effectively reduce The impact of electromagnetic interference, since the implementation in October 2010, the electromagnetic interference problem of the air compressor station control system has been effectively solved.
The machine is a
semi-Automatic Welding Machine for the welding of vertical pole cuplock, which
can realize the process of automatic spot welding, automatic girth welding and
automatic unloading of the cuplock vertical pole.
Description of cuplock scaffolding
Automatic Welding Machine
Guarantee time: 1
year
MOQ: 1 set
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Delivery: Tianjin
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70% TT paid before shipment or against B/L copy.
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