In industrial automation and new energy vehicle drive systems, motors serve as the core actuators, and the stability and accuracy of their drives are directly linked to the overall system’s performance and safety. However, whether it is AC motors driven by industrial frequency converters or permanent magnet synchronous motors in new energy vehicles, the power switching devices in their drive circuits generate steep voltage and current gradients during high-speed switching operations, exciting a wide spectrum of electromagnetic noise ranging from tens of kHz to several MHz. These high-frequency interferences not only affect the control precision of the motors themselves through conduction and radiation—causing torque ripple, speed fluctuations, or even positioning deviations—but can also interfere with other sensitive electronic equipment on the same power grid or vehicle platform. In this complex and demanding electromagnetic environment, feedthrough capacitors have emerged as key components for suppressing conducted electromagnetic interference in motor drive systems and ensuring electromagnetic compatibility (EMC), thanks to their superior physical structure and electrical characteristics.
The core advantage of feedthrough capacitors lies in their unique “through-type” design, which enables ultra-low equivalent series inductance (ESL). Unlike traditional leaded or surface-mount capacitors, current flows directly through the capacitor dielectric, creating the shortest possible current path and grounding loop, thereby reducing parasitic inductance to below 1nH. This characteristic means that even when faced with the typical high-frequency switching noise in motor drives, feedthrough capacitors can maintain extremely low impedance, providing an efficient discharge path for such noise. This allows the noise to be channeled into the system’s grounding plane rather than coupling into power or signal lines for further propagation.
From selection to installation, the application of feedthrough capacitors is a precise engineering art. The capacitance value must be carefully chosen based on the spectral characteristics of the target noise, the system’s operating voltage, and the required insertion loss curve. Their metal housing must achieve a large-area, low-impedance connection with the drive’s metal baseplate or dedicated grounding busbar to ensure that high-frequency noise is effectively “shorted” to ground. As motor drive technology advances toward higher switching frequencies and greater power density, the demands for feedthrough capacitors’ high-frequency performance, voltage rating, and temperature stability are also increasing. In the future, integrated and modular filtering solutions will become more favored, and feedthrough capacitors, as an indispensable high-frequency filtering cornerstone, will continue to play a silent yet powerful protective role in enhancing the reliability of motor drive systems and supporting the advancement of electrification and automation processes.
