ABSTRACT
This chapter extends steady-state sinusoidal analysis to circuits that include magnetic coupling between current-carrying coils. This type of coupling is described in terms of a fourth circuit parameter, namely, the mutual inductance between the coupled coils. The linear variable differential transformer (LVDT) is a useful device for measuring displacement. It consists of a transformer having two secondary windings on either side of the primary winding and connected in series opposition. Ferrites made of manganese and zinc oxides or nickel and zinc oxides are linear, at least under normal operating conditions, whereas those containing iron oxide are generally nonlinear. Circuits involving ideal transformers can be conveniently analyzed by reflecting the circuit on the primary side to the secondary side, or conversely. The mutual inductance of two magnetically coupled coils is the flux linkage in one coil per unit current in the other coil. The cores of high frequency and pulse transformers are often made of high-resistivity material to reduce eddy currents.
