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A transformer couples two or more AC signals through a magnetic field. Often used as galvanic isolation and to transform one AC voltage to another.

A transformer couples two or more AC signals through a magnetic field. Often used as galvanic isolation and to transform one AC voltage to another.

There are several types of transformer:

Step down transformer The most common type used in electronics to reduce the voltage of a mains supply to a low voltage (typically 12v or 5v), as the first stage in the power supply. This provides isolation of the low voltage circuit from the mains supply.

Auto transformer Transformer where input and output(s) are on the same coil. This does not provide isolation.

Audio transformer Used for impedance matching in audio circuits.

3 phase transformer Used in power transmission systems.

Transformers have a number of specifications used to identify it for use in a particular circuit:

  • Primary Voltage - the supply voltage.
  • Secondary Voltage - the output voltage.
  • Power rating - the load the transformer is designed to operate with, measured in VA (in most cases, i.e. resistive loads, this is equivalent to Watts).

Schematic Symbol:

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