Electromagnetic interference (EMI) can come from various sources such as power networks, electrical equipment transients, lightning, radio, TV, radar, and high-frequency heating devices. This type of interference is often referred to as radiation and can be very complex in distribution. If a PLC system is placed within an RF field, the radiation can cause issues by directly inducing signals into the circuit or through communication lines that pick up interference. The severity of this interference depends on the size and frequency of the electromagnetic field generated by nearby equipment. To mitigate these effects, shielding cables, partial PLC shielding, and high-voltage bleeders are commonly used. Conducted interference comes from external leads such as power and signal lines, which is particularly common in industrial environments. This type of interference is often more severe and can lead to significant problems in PLC operations. For example, a project I worked on had issues due to power supply interference, which were resolved by replacing the power supply with one offering better isolation. Power grids are widely distributed, making them susceptible to induced voltage and current fluctuations. Switching operations, large equipment start-ups, and harmonic distortions can all introduce disturbances into the power supply. While isolated power supplies are typically used, they may not provide perfect isolation due to factors like distributed capacitance. This means some level of interference can still reach the PLC system. Signal lines can also be a source of interference. They not only carry useful signals but can also pick up unwanted noise. One common issue is power grid interference entering through the power supply of a transmitter or shared signal meter, which is often overlooked. Another is electromagnetic radiation affecting the signal line itself, causing serious disruptions. These interferences can lead to abnormal I/O behavior, reduced measurement accuracy, and even component damage. In systems with poor isolation, signals can interfere with each other, causing logical errors, data corruption, or system crashes. Grounding plays a crucial role in improving electromagnetic compatibility (EMC). Proper grounding helps suppress both internal and external interference. However, incorrect grounding can create ground loops and introduce harmful currents. For instance, if a cable's shield is grounded at both ends, a potential difference between the two points can cause current flow, especially during events like lightning strikes. This can lead to additional interference and instability in the system. Interference from within the PLC system itself, such as electromagnetic coupling between internal components, can also affect performance. Logic circuits may interfere with analog circuits, and improper grounding between different parts of the system can lead to operational issues. While these problems are typically addressed during the design phase by manufacturers, it’s important for users to choose reliable systems and perform thorough testing. Dell Certified Refurbished,Refurbished Dell Computers,Used Dell Computers,Used Dell Laptops For Sale Guangzhou Panda Electronic Technology Co., LTD , https://www.panda-3c.com
PLC control system electromagnetic interference source analysis - Database & Sql Blog Articles
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