In the design and operation of industrial control systems, electromagnetic compatibility is a pervasive and fundamental challenge. The industrial field environment is complex, with high-power equipment such as variable frequency drives, motors, and relays frequently starting and stopping, injecting substantial high-frequency transient noise into the power grid. Simultaneously, external radiation interference from wireless communications, radar, and other sources is ever-present. These interferences couple into the industrial control computer through power and signal lines, ranging from causing data acquisition errors and communication bit errors to triggering system crashes or control failures, directly impacting production continuity and safety. Against this backdrop, feedthrough capacitors have emerged as key components in building the electromagnetic defense line for industrial control systems, thanks to their unique electrical characteristics and structural advantages.

The inherent strength of feedthrough capacitors stems from their design, which breaks through the physical limitations of traditional capacitors. Conventional capacitors, due to their leads or pads, introduce parasitic inductance on the order of several nanohenries, significantly degrading their high-frequency filtering performance or even rendering them entirely ineffective in the target frequency bands. In contrast, feedthrough capacitors employ a “through-type” coaxial structure, where the signal or power line passes directly through the capacitor dielectric. This minimizes the current path and grounding loop, reducing self-inductance to below 1nH. This characteristic enables their self-resonant frequency to easily extend into the GHz range, allowing them to maintain near-ideal capacitor impedance characteristics—stable and highly effective filtering—within the frequency bands where industrial interference is most concentrated, from several hundred kHz to several hundred MHz. Moreover, their input and output terminals are physically separated by a complete metal plate, fundamentally blocking the path for high-frequency interference to “bypass” the capacitor through electric field coupling. This achieves true “feedthrough filtering,” making them particularly effective at suppressing crosstalk between lines and common-mode noise.

Furthermore, in the face of the compact, space-constrained interior of industrial control computers and the growing trend toward modularization and high-density integration, the miniaturized packaging of feedthrough capacitors offers significant advantages. Their cylindrical or block-shaped form factors can be made extremely compact, allowing them to be installed directly in PCB mounting holes or on the walls of shielded enclosures, occupying almost no additional valuable board area. This “embedded” installation method not only saves space but also, by connecting directly to the metal chassis or a large-area ground plane, achieves excellent high-frequency grounding effects, maximizing filtering performance.