Designing An Open-Source Power Inverter (Part 24): Inverter Output Filter Conundrum

Focus:

As the Volksinverter design series winds down, this part addresses the conducted EMI produced by the inverter stage and the design of the LC filter to attenuate this EMI. The author analyzes operation of the LC filter, and discusses different possible solutions to suppress common-mode currents on the inverter output. This analysis explains why the author changed the LC filter from the original design with coupled inductors presented in part 5 to the modified design with uncoupled inductors presented in part 23. In this part, he also analyzes how PWM switching sequences affect EMI performance and which sequences are optimal; and presents design equations for the output filter.

What you’ll learn:

• How to understand the impact of coupled versus uncoupled inductors in suppressing common- mode currents in LC output filters
• How to understand the impact of PWM switching sequences on generation of common-mode currents in inverters
• How to design the LC output filter for a power inverter

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Author & Publication:

Dennis Feucht, Innovatia Laboratories, Cayo, Belize, How2Power Today, Feb 14 2025

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