ABB XVC768101 3BHB007211R0101 circuit board module in stock

Description

The interference in the control system and its source on-site electromagnetic interference are one of the most common and easily affecting factors in the reliability of the PLC control system. The so-called “addressing the symptoms first, identifying the root cause, and then proposing solutions to the problem. Therefore, it is necessary to know the source of on-site interference.

(1) The interference sources and their general classification affect the PLC control system. Most of the interference sources occur in areas with drastic changes in current or voltage. The reason for this is that the current changes generate magnetic fields, which generate electromagnetic radiation on the equipment; Magnetic field changes generate current, and electromagnetic waves are generated at high speeds. Usually, electromagnetic interference is divided into common mode interference and differential mode interference according to different interference modes. Common mode interference is the potential difference between a signal and ground, mainly formed by the superposition of the common state (in the same direction) voltage induced by the grid connection, ground potential difference, and spatial electromagnetic radiation on the signal line. The common mode voltage can be converted into differential mode voltage through asymmetric circuits, directly affecting the measurement and control signal, causing component damage (which is the main reason for the high damage rate of some system I/O modules). This common mode interference can be DC or AC. Differential mode interference refers to the interference voltage acting between the two poles of a signal, mainly formed by the coupling induction of spatial electromagnetic fields between signals and the conversion of common mode interference by unbalanced circuits. This interference is superimposed on the signal and directly affects the measurement and control accuracy.

(2) The main source and pathway of interference in the PLC system is strong electrical interference. The normal power supply of the PLC system is powered by the power grid. Due to the wide coverage of the power grid, it will be subjected to all spatial electromagnetic interference and induce voltage on the line. Especially the changes within the power grid, such as surges caused by knife switch operation, start-up and shutdown of large power equipment, harmonics caused by AC and DC transmission devices, and transient impacts caused by power grid short circuits, are all transmitted to the power source through transmission lines. High voltage electrical appliances inside the cabinet, large inductive loads, and chaotic wiring can easily cause a certain degree of interference to the PLC. The interference introduced by the signal line and various signal transmission lines connected to the PLC control system, in addition to transmitting effective information, will always be invaded by external interference signals. There are two main ways for this interference: firstly, it is caused by the power supply of the transmitter or the power supply of the shared signal instrument connected in series to the power grid, which is often overlooked; The second is that the signal line is interfered by the induction of spatial electromagnetic radiation, that is, external induced interference on the signal line, which is very serious. Introducing interference from signals can cause abnormal operation of I/O signals and greatly reduce measurement accuracy, and in severe cases, it can cause component damage. Grounding is one of the effective means to improve the electromagnetic compatibility (EMC) of electronic equipment due to interference from chaotic grounding systems. Proper grounding can not only suppress the impact of electromagnetic interference but also suppress external interference from equipment; However, incorrect grounding can actually introduce serious interference signals, making the PLC system unable to function properly.

4911014-SNM
3BUC640023R1
3BUC950040R1
3BUR000546R1
3BUR000548R2
3BUR001399R1
3BUR001400R1
3BUR001661R1
3BUR002086R1
3BUR002123R1
3BUR002124R1
3BUR002125R1
3BUR002253R1
3BUR002254R1
3BUR980001R1
3BUR980024R1
3BSC950120R1
3BSE018448R1
3BSE018450R1
57160001-NF
57160001-NL
57160001-NR
57160001-NV
57160001-P