Page 109 - Louth Transformer Catalogue

LT DATA

WHAT IS A TRANSFORMER?

WINDINGS
The wire used in a transformer is usually solid copper magnet wire with an insulated coating, in order to
electrically insulate adjacent turns in the coil from each other to ensure that current travels through the
entire winding. Extra tape insulation is usually provided between winding layers in larger transformers.

Windings on both the primary and secondary coils may have taps to enable adjustment of the voltage
ratio. A centre tapped transformer is often used in the output stage of an audio power amplifier in a
push-pull type circuit. Tapped transformers are also used as amplifier components. Transformers can
also be manufactured with multiple primary and secondary windings, to allow for multiple step-up
and/or step-down ratios in the same device. A variable transformer can also be made by providing
a moveable arm that sweeps along the length of the winding, making contact at any point along its
length.

OPERATING AT DIFFERENT FREQUENCIES

By operating at higher frequencies, transformers can be physically more compact without reaching
saturation, and a given core is able to transfer more power. However, other properties of the
transformer, such as losses within the core and skin-effect, also increase with frequency. Generally,
operation of a transformer at its designed voltage but at a higher frequency than intended will lead
to reduced magnetising current. At a frequency lower than the designed value, with the rated voltage
applied, the magnetising current may increase to an excessive level.

A transformer designed for 50Hz will work at 60Hz; however a transformer designed for 60Hz may be
damaged if required to work at 50Hz.

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