Numerical methods and measurement systems for networks containing magnetic nonlinearities

Abstract

ContentsIn the last years an increasing interest in computer aided circuit calculation methods could be observed. This can be seen in combination with the short innovation processes in commercial products. Especially there is a need in modelling of nonlinear magnetic elements. In order to overcome these problems, a new method was developed, which makes it possible to calculate the steady state solution of circuits containing nonlinear magnetic elements by the help of an interactive CAD-program. After separating the network into linear and nonlinear subnetworks, it is possible to choose between several models for the nonlinear elements. In applications, where numerical models are insufficient a realtime measurement system can be activated to extract the nonlinear behaviour (dynamic hystersis loops). This concept is discussed for earth-leakage circuit breakers. These networks contain a toroidal highly permeable NiFe-alloy and a relay as nonlinear elements and some resistors, inductors and capacitors as linear elements. AC-signals at the primary winding of the core in any waveform must be regarded as an input, 135 degree phase cut off sinusoidal signals are especially important. These signals with extreme high frequency components make it impossible to use numerical models for the description of the nonlinear behaviour of the core and the relay. Therefore for both elements the realtime measurement system must be used during the iteration process.