Simulation of a 3-phase common- and differential mode inductor on a four-limb core

Abstract:
An optimized method to simulate the common- mode and differential mode inductance and the core loss of a four limb inductor is presented here. Ordinary sinusoidal filters, which have a common- and differential mode filter effects, consist of two inductors (Figure 1). In the case of a four-limb core, the two inductors can be accommodated on a common core. The fourth limb is required to lead the common mode magnetic flux. With only three limbs and a phase balance of the common-mode currents, the magnetic flux would be zero at the magnetic neutral point [1]. Due the non-linearity of the Hysteresis it is not possible to calculate the core losses by using the superposition method. A transient model, which is based on the principal of loss separation, is used, to calculate the core losses of the four-limb inductor. The core losses of electrical steel are measured with a special measurement system, which can simulate typical waveforms for inductors in power electronic applications. Finally, measurement and simulation results are compared.