What is electromagnetic interference in power electronic circuits?

Dear Vahid
Three major issues in designing a power electronic system are Losses, EMI (Electromagnetic interference) and Harmonics. These issues affect system cost, size, efficiency and quality and it is a trade-off between these factors when we design a power converter. In power electronics, high voltages and high currents are processed by fast switching to reduce losses which are significant sources of electromagnetic noise and it cause additional costs.

Two major sources of EMI in power electronics are dv/dt and di/dt during switching times. In fact, a DC voltage of few hundred volts is chopped by a power switch in a fraction of microsecond. Thus, conducted emission is a major issue in most power electronic systems due to significant over voltage and leakage current generated by fast switching and stray components of the system.
- High di/dt may create significant over voltage in power converters due to stray inductance of current loops.
- High dv/dt may create significant leakage current in magnetic elements and electric motors due to stray capacitive coupling between windings and a frame.