Use of Transformers

Purpose of Transformers

Transformers are electrical devices used to change the voltage of alternating current (AC) electricity. Their main purpose is to either increase or decrease voltage levels depending on the need.

• Step-up transformers increase the voltage from the primary coil to the secondary coil.
• Step-down transformers decrease the voltage from the primary coil to the secondary coil.

By changing voltage levels, transformers enable efficient transmission of electrical power over long distances. High voltages are used to reduce energy loss during transmission, while lower voltages are used to make electricity safe for domestic and commercial use.

How Transformers Work

Transformers operate on the principle of electromagnetic induction, which is the process where a changing magnetic field induces a voltage in a coil (covered in other topics), but here we focus on their use:

• An alternating current in the primary coil creates a changing magnetic field.
• This changing magnetic flux passes through the iron core and induces a voltage in the secondary coil.
• The voltage induced in the secondary coil depends on the ratio of the number of turns in the primary coil to the number of turns in the secondary coil.

If the secondary coil has more turns than the primary coil, the voltage increases (step-up). If it has fewer turns, the voltage decreases (step-down).

For instance, if a transformer has 100 turns on the primary coil and 200 turns on the secondary coil, the voltage in the secondary coil will be twice the voltage in the primary coil, stepping the voltage up.

Use in the National Grid

The National Grid is the system that distributes electricity across the UK. Transformers play a vital role in this system to ensure electricity is transmitted efficiently and safely:

• Step-up transformers increase the voltage from power stations to very high levels (hundreds of thousands of volts) for transmission across long distances.
• Increasing voltage allows the current to be reduced for the same power output, which reduces energy lost as heat in the cables.
• Step-down transformers near towns and homes reduce the high voltage to safer, usable levels (around 230 V) for domestic and commercial use.

This system minimises energy loss and ensures safety for consumers.

For example, if electricity is transmitted at 400,000 V instead of 230 V, the current is much lower, and since energy loss due to resistance in cables depends on the square of the current, losses are greatly reduced.