What impact does the load have on the EMC testing of the frequency converter?

Load conditions have a significant impact on the EMC test results of frequency converters, and representative loads must be considered during testing.

Load effects include: load type (resistive, inductive (motor), or capacitive loads) affects the inverter's output current waveform, switching transistor stress, and feedback energy, thus influencing the noise spectrum; load size (light and heavy loads result in different switching losses, current ripple, and potentially different conducted and radiated noise levels); motor cable length (as part of the load), where parasitic parameters interact with the output filter, potentially triggering resonance and affecting radiation at specific frequencies; and motor characteristics, such as the motor's capacitance to ground, which affect the common-mode current loop.

Therefore, EMC certification testing typically requires testing under rated or typical load conditions. Pre-testing in R&D should also use load conditions similar to those in actual applications to ensure the validity of test results. Using purely resistive loads during testing may yield results different from those with a motor load. Load conditions during testing should be recorded, and the impact of load changes on EMC should be analyzed when problems arise. The output filter design of Audiotech also considers different load conditions.