Flanagan Transformers - How a transformer works, transformer basic principals

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Transformer Fundamentals

How to order

To order a transformer you will need to know -

Input voltage (single or three phase?)
Output voltage
Output current or power required

You will also need to advise if there are any special circumstances that will affect the final design, such as -

High temperature / humid conditions
Size or weight restrictions
Duty cycle (ie. 60% on 40% off)

Basic principals

A simple transformer consists of two electrical conductors called the primary winding and secondary winding, and a steel core that magnetically links them together

These two windings can be considered as a pair of mutually coupled coils. Energy is coupled between the windings by the magnetic field that links both primary and secondary windings.

Classifications

Transformers are adapted to numerous engineering applications and may be classified in many ways:

By power level (from fraction of a VA to over a thousand MVA),
By application (power supply, impedance matching, circuit isolation),
By frequency range (power, audio, RF)
By voltage class (a few volts to about 750 kilovolts)
By cooling type (air cooled, oil filled, fan cooled, water cooled, etc.)
By purpose (rectifier, arc furnace, amplifier output, etc.)

By ratio of the number of turns in the coils -

Step up
Step down
Isolating
Variable

Circuit symbols

Two windings and an iron core, step-up or step-down as windings are different ratios.

Transformer with two windings and an iron core.

Transformer with three windings, two secondary windings.

Transformer with an earth screen.

Three phase circuit symbols

The three primary windings are connected together and the three secondary windings are connected together. This is also sometimes referred to as a polyphase transformer.

The most common connections are Y-A, A-Y, A-A and Y-Y.

There are many possible configurations that may involve more or fewer than six windings and various tap connections.

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