AI server power supplies generate switching noise that can travel into the rack and out to the grid – and a feedthrough capacitor is one of the most effective ways to keep that EMI at the power entry point. As AI servers push power consumption to 175 TWh in 2026, the EMI filtering on their power supplies matters more than ever.

Switching power supplies in AI servers switch at high frequency, and every switch edge produces conducted and radiated interference. Left unfiltered, that noise disrupts other equipment in the rack and can fail EMC compliance. Feedthrough capacitors sit on the power line and shunt high-frequency noise to ground while letting DC through – exactly what a server PSU input needs.

Why AI Power Supplies Need EMI Filtering

• Fast switching edges (high dv/dt) from power stages generate broadband noise.
• Dense racks mean many PSUs in close proximity, so noise from one can couple into another.
• Compliance limits (CISPR/FCC-style) apply to the whole server or rack.

The Role of the Feedthrough Capacitor

A feedthrough capacitor passes the DC line through its centre while its outer electrode connects to the chassis ground. High-frequency noise is bypassed to ground rather than passed along. Because it is a true through-line component, it keeps high-frequency performance that ordinary two-terminal capacitors lose at frequency. Our guide to high-frequency interference feedthrough capacitors covers the behaviour in detail.

The EMI environment around AI racks is getting harder: more PSUs, higher switching frequencies and tighter compliance margins all push the power entry to do more filtering in less space.

What to Specify for AI Power Supply EMI Filtering

• Capacitance – pick for the frequency range you need to suppress.
• Voltage and current rating – match the PSU input rail.
• Insertion loss at your switching frequency – the real measure of filtering performance.
• Mounting – panel or solder-in feedthroughs; see Xuansn threaded feedthrough capacitors.

Common Questions About Feedthrough Capacitors in AI Power Supplies

Where do feedthrough capacitors go in a server PSU?

At the AC or DC power entry, between the connector and the rectifier or switch-mode stage, to bypass conducted noise to chassis ground.

Why use a feedthrough capacitor instead of a normal capacitor?

A feedthrough capacitor keeps its filtering performance at high frequency because the line passes through it, unlike a two-terminal capacitor whose leads add inductance that degrades high-frequency bypassing.

How do I choose the capacitance for AI PSU EMI filtering?

Choose based on the target frequency band and the required insertion loss; higher capacitance filters lower frequencies, while the feedthrough structure preserves performance at high frequencies.

More on AI Power and EMI

AI server power demand is reshaping power design here. For the fundamentals, see what a filter capacitor is and anti-RFI design with feedthrough filters.

Need feedthrough capacitors for AI power or EMC filtering? Xuansn Capacitor manufactures feedthrough and EMI filter capacitors – our engineers will reply within 24 hours with feasibility and a quote.

✉ sales1@xuanxcapacitors.com | ☎ +86-769-8166 8821 | Send your specification

Sources: Gartner data center electricity forecast, June 2026 (AI-optimized servers 175 TWh, up 84%).