In power electronic equipment, inverters play a central role in converting DC to AC energy, and the stability of their performance directly affects the reliability of the entire system. However, it is precisely this high-frequency, high-power energy conversion process that makes inverters one of the primary sources of electromagnetic interference. When switching devices rapidly turn on and off, steep voltage and current gradients form in the circuit, generating electromagnetic noise ranging from tens of kHz to several MHz or even higher frequencies. This noise can not only interfere with surrounding equipment through spatial radiation but also conduct to other parts of the system through power lines, DC busbars, or signal loops. In severe cases, it can even cause disturbances in the inverter’s control logic, false protection triggering, or damage to power components. Against this backdrop, feedthrough capacitors have become key components in suppressing conducted interference in inverters and enhancing electromagnetic compatibility, thanks to their low inductance and high-frequency response characteristics.
The unique structure of feedthrough capacitors determines their advantage in high-frequency filtering. Unlike traditional capacitors, they employ a through-type design, allowing current to flow directly through the capacitor dielectric, effectively reducing the parasitic inductance introduced by leads. This enables them to maintain low impedance at frequencies as high as tens or even hundreds of MHz, creating a low-impedance path for switching noise and efficiently channeling it to the ground plane. In inverter design, feedthrough capacitors are often used in synergy with inductors to form composite filtering networks. For example, on the AC output or DC input side of an inverter, a Pi-type filter structure can be adopted: feedthrough capacitors are placed at both ends of the filter, with an inductor connected in series in the middle. This configuration not only filters external interference from the grid or DC power supply but also effectively suppresses the outward conduction of noise generated by the inverter itself, providing bidirectional purification.
It is worth noting that the selection and installation techniques of feedthrough capacitors are critical to their performance. Capacitance selection must be tailored to the target noise frequency band, while during installation, it is essential to ensure a large-area, low-impedance connection between the metal housing of the capacitor and the system’s grounding layer to establish a complete return path for high-frequency noise. As inverter technology advances toward higher switching frequencies and greater power density, feedthrough capacitors continue to evolve with higher voltage resistance, broader temperature adaptability, and enhanced high-frequency characteristics, becoming an indispensable foundation for noise management in the next generation of highly efficient and reliable inverter systems.
