ABSTRACT
The transformer forms the basis of all ac power-distribution systems. In the most basic definition, a transformer is a device that magnetically links two or more circuits for time-varying voltage and current. Magnetic coupling has a number of intrinsic advantages, including:
• DC isolation between the circuits • The ability to match the voltage and current capability of a source to a load • The ability to change the magnitude of the voltage and current from one side of the transformer to the other • The ability to change the phases of voltage and current from one side of the device to the other
Inductance is, primarily, a geometrical property of a current-carrying element in an electrical circuit [1]. A circuit element with this property may be termed an inductor. The magnitude and, for that matter, the frequency dependence of inductance also depend on the material environment of that element. Similar remarks to these could — of course — be used to define capacitance; inductance and capacitance are invariably intimately related in electronic circuits. One reason is that both are (electrical) energy storage devices in time-varying electronic systems. Capacitance is, however, a measure of the capability of a (potential) circuit element to store charge and, thereby, electric field energy; inductance, by contrast, is a measure of a circuit element’s ability to store magnetic field energy. Because a magnetic field is derived from current flow, inductance is always associated with current-carrying circuit elements. This dichotomy extends also to the matter of frequency dependence. At zero signal frequency, for example, an (ideal) capacitor has infinite impedance, whereas the inductor has zero impedance; at infinite frequency, the opposite is true.
