Measurement and Modeling of the Magnetic Near Field Radiated by a Buck Chopper

Static converters are used with increasingly high switching frequencies. Consequently, they impose increasingly severe electromagnetic interference (EMI) constraints in their environment. In order to study and to quantify the radiated perturbations, we have used a test bench for measuring the magnetic field radiated in the near zone. In this paper, we present measurements of the magnetic field radiated by the switching cell of a Buck chopper in the near field at high and low frequencies. By comparing the mappings of the magnetic field over the switching cell with the ones of a circular loop, we have deduced that the switching cell can be effectively modeled by a loop. The loop's geometric characteristics and its equivalent current flowing in have been determined from near magnetic field data. The model has been validated at high and low frequencies.