Shorted Turns Detection

Introduction to Shorted Turns

Inductors are made up of a length of wire, usually wound around a core.

The core is usually some type of magnetic material such as iron or ferrite, however air cores are also sometimes used.

The wire, is referred to as the “winding”, and this winding is made up of a number of turns.

Generally, inductors are a single winding, and transformers mostly have multiple windings, (there are special cases, such as “Auto transformers” where only a single winding exists) and in many transformers different wire diameters can be used in the various windings.

Inductors and/or transformers that are wound using a large number of turns and/or using very fine wire, require a method of detecting the existence of shorted turns, and also the ability to stress the winding in order to detect imperfections or potential weaknesses in the winding insulation that could be a weak point over time.

Winding imperfections can normally be attributed to damaged enamel caused by physical damage during manufacture of the transformer, or imperfections during the manufacture of the raw wire itself.

These imperfections can result in shorted turns during normal operation if undetected at point of manufacture.

The high temperatures resulting from the increased current at the short will fairly quickly cause copper melting and create a low resistance spot weld.

This low resistance short will then completely short out one turn, affecting the performance of the winding and hence the whole transformer