Transformers: A transformer is a static unit. It simply transforms the voltage level of an AC signal. It either steps up or steps down the AC voltage. It works on the principle of electromagnetic induction. A transformer does not change the frequency of applied AC signals. Transformers play an important role in the electrical systems. 

1. Transformers are available in a number of sizes. For example, a transformer used in a mobile charger is very small, whereas transformers used in the substation of an electricity board are big.

2. High voltage is used for transmission and low voltage is used in offices and at home.

3. Transformers are used to increase or decrease AC voltage in transmission and distribution of electricity.

4. Basic construction of the transformer includes two coils wound on the magnetic frame or core.

5. Both the coils are magnetically coupled, whereas they are electrically insulated from each other.

6. The primary or input coil is connected to the energy source, while secondary or output coil supplies power to load.

7. Electromagnetic induction is used in a transformer. In power grids, large transformers are used. These transformers are used in the generation, distribution and transmission in the electrical systems. Transformers are placed in every location from the generator to the user.

One of the main reasons that we use alternating AC voltages and currents in our homes and workplace’s is that AC supplies can be easily generated at a convenient voltage, transformed (hence the name transformer) into much higher voltages and then distributed around the country using a national grid of pylons and cables over very long distances.

The reason for transforming the voltage to a much higher level is that higher distribution voltages implies lower currents for the same power and therefore lower I2*R losses along the networked grid of cables. These higher AC transmission voltages and currents can then be reduced to a much lower, safer and usable voltage level where it can be used to supply electrical equipment in our homes and workplaces, and all this is possible thanks to the transformer basics of the Voltage Transformer.

voltage transformer basics

A Typical Voltage Transformer

The Voltage Transformer can be thought of as an electrical component rather than an electronic component. A transformer basically is very simple static (or stationary) electro-magnetic passive electrical device that works on the principle of Faraday’s law of induction by converting electrical energy from one value to another.

The transformer does this by linking together two or more electrical circuits using a common oscillating magnetic circuit which is produced by the transformer itself. A transformer basics operate on the principals of “electromagnetic induction”, in the form of  Mutual Induction.

Mutual induction is the process by which a coil of wire magnetically induces a voltage into another coil located in close proximity to it. Then we can say that transformers work in the “magnetic domain”, and transformers get their name from the fact that they “transform” one voltage or current level into another.

Transformers are capable of either increasing or decreasing the voltage and current levels of their supply, without modifying its frequency, or the amount of electrical power being transferred from one winding to another via the magnetic circuit.

A single phase voltage transformer basically consists of two electrical coils of wire, one called the “Primary Winding” and another called the “Secondary Winding”. For this tutorial we will define the “primary” side of the transformer as the side that usually takes power, and the “secondary” as the side that usually delivers power. In a single-phase voltage transformer the primary is usually the side with the higher voltage.

These two coils are not in electrical contact with each other but are instead wrapped together around a common closed magnetic iron circuit called the “core”. This soft iron core is not solid but made up of individual laminations connected together to help reduce the core’s magnetic losses.

The primary and secondary windings are electrically isolated from each other but are magnetically linked through the common core allowing electrical power to be transferred from one coil to the other. When an electric current passed through the primary winding, a magnetic field is developed which induces a voltage into the secondary winding and this transformer basics operating principle.

What is a transformer used for?

Transformers have two primary functions: Voltage transformation and isolation:

  • The voltage of the secondary can be higher or lower than the voltage that drives the primary and is determined by the ratio of turns of wire in the two coils.
  • Isolation refers to the fact that the coils are connected only by a magnetic field, so they can be independent of a common ground.

Primary applications are for power and for signal isolation / impedance transformation.

An autotransformer is a transformer with a single coil with intermediate "taps" to effect the changed outgoing voltages. They do not provide isolation.

Transformer capacity is rated in kilovolt-amps (KVA): The volts x amps / 1000.