How to rectify the conducted emission failure of frequency converter?

To rectify issues arising from failed conducted emissions tests of frequency converters, a systematic analysis of the out-of-range frequency bands and targeted measures are necessary. Conducted emissions are typically tested in the 150kHz-30MHz frequency band.

Rectification steps include: analyzing the test report to determine the out-of-range frequency points and amplitudes; determining the nature of the noise based on the frequency points (low-frequency bands may originate from switching frequency harmonics, while high-frequency bands may originate from switching overshoot or diode reverse recovery); checking and optimizing the input EMI filter: ensuring the common-mode inductor (e.g., the CMZ7060A series) has sufficient inductance and still provides impedance at high frequencies; checking the capacitance and installation of the X and Y capacitors; and ensuring proper filter grounding.

Strengthening internal noise suppression: checking the high-frequency characteristics of the DC bus capacitors (parallel film capacitors can be connected); optimizing the IGBT drive to reduce overshoot; and checking for RC absorption in the rectifier diodes.

Checking installation and wiring: ensuring the filter is installed close to the power input; separating input and output cables; and ensuring low impedance grounding connections. For specific frequency points, ferrite cores can be added to the input lines.

Verifying the effectiveness of the rectification measures item by item using pre-testing equipment (LISN + spectrum analyzer). Audiotech's filters, capacitors, and magnetic rings offer a wide range of options for conducted emission rectification.