Leakage inductance is that property of an electrical transformer that causes a winding to appear to have some pure inductance in series with the mutually-coupled transformer windings. Transformers - Typical electrical configurations. ... Inductance is a physical characteristic of an inductor, which is an electrical device that produces at any time a voltage proportional to the instantaneous rate of change in current flowing through it. ...

Usually, this is an undesirable property, but it is sometimes deliberately introduced into a transformer that is used as a ballast for a gas discharge lamp such as a neon sign, fluorescent lamp, or a high-intensity discharge lamp. In this case, the leakage inductance limits the current flow to the desired magnitude. (Without the leakage inductance, the negative resistance characteristic of these gas discharge lamps would cause them to destroy themselves by conducting too much current.) Ballast may mean: track ballast: gravel or cinders forming the railroad or railway track-bed on which sleepers (ties) and track is laid, for proper drainage ships ballast: water, sand, rocks, or bricks used to weight a ship down when it has very little cargo (though water may contain... -1... The acronym LAMP refers to a set of free software programs commonly used together to run dynamic Web sites or servers: Linux, the operating system; Apache, the Web server; MySQL, the database management system (or database server); Perl, PHP, and/or Python, scripting languages. ... a neon sign at night Neon signs are produced by the craft of bending glass tubing into shapes. ... A compact fluorescent lamp with an integrated electronic ballast A fluorescent lamp is a type of lamp that uses electricity to excite mercury vapor in argon or neon gas, producing short-wave ultraviolet light. ... High-intensity discharge (HID) lamps include the groups of electrical lights commonly known as mercury vapor, metal halide, high-pressure sodium, and xenon short-arc lamps. ... In electricity, current is the rate of flow of charges, usually through a metal wire or some other electrical conductor. ... In electrical circuits, static resistance is the ratio of the voltage across a circuit element to the current through it. ...

Leakage inductance is primarily controlled by the design of the core and the wire windings used to form the transformer. It can have a significant effect on cross regulation - the regulation of one output of a power supply when another is loaded.

Further Reading

Texas Instruments Magnetics Design Handbook covers leakage inductance, it's causes and effects as well as how to design it out of a transformer.