Discussion on AC contactor control technology of t

  • Detail

Discussion on AC contactor control technology of emulsified modified asphalt equipment

Abstract: from the perspective of AC contactor control technology, this paper analyzes and discusses the new technologies and methods used in AC contactor products at the present stage, and puts forward views on the further application of high and new technologies such as artificial intelligence technology, computer technology and communication technology in AC contactor products

key words: AC contactor intelligent artificial intelligence

1 introduction

AC contactor is an indispensable low-voltage electrical product with large quantity and wide range in electric drive and automatic control system. With the rapid development of science and technology, the requirements of power and automatic control systems for AC contactors are increasing. Thus, the control technology, detection technology and production technology of AC contactor have changed fundamentally. A new generation of AC contactors with excellent performance and reliable control are gradually occupying the contactor stage

2 traditional control technology of AC contactor

the principle and technology of electric, magnetic, optical, thermal, mechanical, mechanical, material, insulation, electrical contact, reliability and so on are involved in the working process of AC contactor. The conversion laws of electric, magnetic, optical, thermal, mechanical and other energy are mostly nonlinear, and many phenomena are transient processes, which makes the theoretical analysis, product design and performance test of AC contactors relatively complex. Therefore, it is not easy to design and manufacture AC contactors with small volume, light weight, high service life, excellent performance and reasonable price

2.1 analysis of the working principle of AC contactors

today, we will talk about the matters needing attention of a material tensile testing machine The main products are air AC contactors and vacuum contactors. Air AC contactors are divided into rotating contactors, direct acting contactors, and switching capacitor contactors derived from direct acting contactors. Among them, the air direct acting AC contactor is the AC contactor with the largest consumption. This kind of product is the first generation of contactors CJ10 to cj20 designed and developed by ourselves in the 1960s and the new product CJ40 AC contactor at this stage. There is no fundamental change in the control principle and overall structure. Its working process can be divided into three stages: pull in stage, pull in stage and break off stage

pull in stage refers to the whole process from the contactor coil receiving electricity to the complete closure of the contactor contact. This stage can be divided into touch stage and pull in stage. In the touch stage, the contactor coil is connected to the process of voltage and current increasing until the suction current. In this stage, the suction is less than the reaction force, and the armature has not moved; In the stage of pull in motion, the suction is greater than the reaction force, the armature starts to move, and the air gap gradually decreases until the contact is completely closed

taking CJA AC contactor as a prototype, we have carried out the dynamic calculation of the magnetic system, and obtained the law that the parameters such as voltage, current, displacement, speed, flux linkage, suction, reaction force and so on change with time in the electromagnetic mechanism of the AC contactor during the pull in action

closing phase angle directly affects the whole closing process of AC contactor. When the closing phase angle is different, the dynamic process is very different. Under some phase angles, there will be a non closing phenomenon, which seriously affects the reliability of the contactor. Although it can be reliably closed under some closing phase angles, the closing speed is fast, resulting in serious collision, which directly affects the mechanical life of the contactor. In the traditional design process of AC contactor, it must be ensured that the contactor can be reliably closed under all closing phase angles

in the holding stage, the AC contactor must be reliably closed under the action of single-phase AC power

during the breaking process, the arc generated by the contactor contact system seriously affects the electrical service life of the contactor. Although, the rapid development of new materials and new processes has brought new development space to the traditional contactor contact system. However, the problems such as the bounce when the contact is closed and the arc when the contact is disconnected make the AC contactor have short service life, low operation frequency and long action time

2.2 energy saving control technology of AC contactor

the electromagnetic system of AC contactor generally adopts AC control to adjust the passive needle spring screw power supply. At present, the active power consumed by the electromagnetic system of large and medium capacity AC contactors with rated current of 100A and above produced in China is between ten watts and more than one hundred watts (such as 118 watts for CJA). The active power consumed by iron core and short-circuit ring accounts for more than 90%

the AC contactor with large quantity and wide range not only consumes a lot of electric energy, but also produces serious noise, which affects the working environment. At the same time, the short-circuit ring is the weak link of mechanical life. The energy-saving silent operation of AC contactors can not only save electric energy, significantly reduce noise and improve the working environment, but also reduce the volume of contactors, save copper and iron consumption, significantly reduce temperature rise and improve product reliability

some enterprises study and discuss the energy-saving technology through AC contactors. The control circuit of directional conduction is set, which has the advantages of simple structure, low price and reliable operation

when the power supply voltage is applied to the circuit, the single chip microcomputer judges the power supply voltage. When the voltage is higher than the pull-in voltage, select an optimal closing phase to turn on the main control element. Under a large starting magnetic potential, the contactor coil is energized and the contactor is pulled in. When the contactor is closed, the single-chip microcomputer system turns off the main control element and turns to the low DC voltage and low current holding circuit, so that the contactor can save energy and operate silently. The power-saving controller composed of this circuit can be used together with the AC contactor to form an energy-saving AC contactor, or it can be an independent appliance used together with the contactor or other AC electromagnetic appliances. The energy-saving effect can reach more than 93%

3 intelligent control technology of AC contactors

3.1 intelligent AC contactors

with the rapid development of intelligent networks, the development of a new generation of intelligent AC contactors has become a top priority. After a lot of experimental research and theoretical analysis, the specialized company successfully introduced intelligent technology into the AC contactor, and realized the optimal control of the starting, holding and breaking process of the AC contactor. The following is the control principle of the contactor

Figure 1 control block diagram of intelligent AC contactor

it can be seen from Figure 1 that the single chip microcomputer system controls the main control element 1, the main control element 2 and the freewheeling element through control loop 1, control loop 2 and control loop 3 respectively

(1) starting phase control

during the starting process, the single chip microcomputer system continuously samples the power supply voltage and judges the threshold voltage of the pull in. If the voltage is higher than the threshold voltage of the pull in, then select the corresponding program according to different input voltage values. At the corresponding time (conduction phase angle) of each half wave, the main control element is turned on through control circuit 1 and control circuit 2, and the coil works under strong excitation. After a certain conduction time, the single chip microcomputer system cuts off the main control element 1 and the main control element 2 through the control circuit, and the starting process ends

(2) closing process control

in the holding stage, the holding winding of the secondary winding of the transformer provides a suitable holding voltage, which makes the contactor coil work under low DC current through the freewheeling circuit. The working mode of DC start and DC hold greatly improves the performance index of the contactor. In the whole operation process, the single chip microcomputer system has been detecting the power supply voltage. Once it is found that the power supply voltage is less than the release voltage, it will immediately switch to the control program of synchronous breaking. After a certain time, the control circuit 3 will close the intermittent current components and the contactor coil will be powered off

(3) breaking stage control

in the breaking process, some enterprises have improved the contact system of the contactor, so that the opening distance of the intermediate phase contact is different from that of the next two phases (national patent). After the intermediate phase contact is opened, the A and C phase contacts are opened after about 5ms. By controlling the breaking time of the intermediate phase contact, the three-phase contact can break the circuit before the current zero crossing, so as to realize the synchronous breaking of the three-phase circuit

3.2 intelligent hybrid AC contactors

since the 1970s, Chinese electrical workers have started the research work of hybrid AC contactors. In the starting process, the trigger circuit first sends a trigger signal to the thyristor, turns on the thyristor, and then selects a suitable phase angle to connect the main contact of the contactor, that is, first connect the thyristor circuit, and then connect the contactor contact. In the closed working state, the current of the main circuit passes through the main contact of the AC contactor, and the thyristor is cut off at this time; When the contactor needs to produce breaking action, turn on the thyristor to transfer the current in the circuit to the thyristor, that is, disconnect the main contact of the contactor first, and then disconnect the thyristor circuit to realize arc free breaking

the whole process optimization control of intelligent hybrid AC contactor is realized by using single-chip microcomputer control technology and three single-phase thyristors. A new type of intelligent hybrid AC contactor with high cost performance has been formed. 4. Do not "zero" the load value after clamping the sample

3.3 intelligent design technology and detection technology

with the rapid development of computer technology, CAD, CAE and CAM technology, the design and research of low-voltage electrical appliances have entered a new stage, and the product development cycle has been greatly shortened

3D CAD system integrates design, manufacturing and analysis. Computer aided design includes structural design, solid modeling, property analysis and dynamic display functions. Electromagnetic mechanisms with different structural forms are suitable for electrical appliances with different functions. CAD software has corresponding expert modules, which can easily determine the structural form of electrical appliances according to the performance requirements, reasonably arrange the excitation system and reaction system, and select reasonable contact bridge type, arc extinguishing device, etc

in a word, computer-aided design includes part design, assembly and final assembly. Designers can observe, conceive, modify, study and check electrical products directly on the computer screen, which greatly shortens the design cycle of products, improves the performance indicators of products and improves the working conditions of electrical workers

to develop low-voltage electrical products with excellent performance, advanced testing and inspection methods must be available. At the beginning of system design, we should also consider the testing problem and design for testability at the same time, so as to shorten the development cycle of products. The dynamic testing device of photoelectric electromagnetic appliances, which combines computer technology, sensor technology, power electronics technology and electrical technology, realizes the real-time detection of the dynamic process of electrical appliances. Software measurement technology, data fusion technology and fuzzy recognition technology are applied to solve the problems of soft measurement, which is difficult to directly measure characteristic parameters, careless errors in the dynamic process of electrical appliances, and comprehensive evaluation of electrical performance

the device has been applied to the research and development of new intelligent AC contactors, which plays an important role in the in-depth study of the real-time optimal control of electrical appliances, achieving the optimal operation and greatly improving its performance index

3.4 communication control function

the intelligent AC contactor developed adopts RS-485 bus standard, and its transmission data is two balanced wires, that is, the output end is a double ended balanced driver, and the input end is a double ended differential amplifier. In this way, if the common mode interference noise signal is mixed in the transmission process, the interference noise will cancel each other due to the differential effect of the two terminal input, and the anti-interference ability of the bus will be enhanced. RS-485 bus

Copyright © 2011 JIN SHI