How to design power frequency magnetic field immunity for frequency inverters

The primary goal of power frequency magnetic field immunity design for frequency converters is to prevent interference voltages induced in the internal loops of the equipment by 50/60Hz and its harmonic magnetic fields. This interference can affect sampling accuracy or cause malfunctions. Design measures include: reducing the area of sensitive loops within the equipment, which is the most effective method. For current sampling transformers, Hall sensors, analog input circuits, etc., signal transmission should use twisted-pair cables to utilize their magnetic field cancellation characteristics. Vulnerable circuits should be placed away from strong magnetic field sources, such as input reactors, transformers, and high-current buses. For unavoidable sensitive loops, magnetic shielding can be used, i.e., using high-permeability materials, such as permalloy, to create a shielding cover to enclose the circuit and provide a low-resistance bypass path for the magnetic field. In circuit design, band-stop filters can be used to filter out power frequency and its harmonic components. For current sensors using the Hall principle, which may be sensitive to stray magnetic fields, models with built-in shielding or strong anti-interference capabilities should be selected. The design effectiveness should be verified through power frequency magnetic field immunity testing. Audiotech Electronics can provide guidance on the selection of magnetic shielding materials and related filtering devices.