Question

Explain how an AC electric generator works and how AC power is transformed and why inside a transformer

Answer 1

AC GENERATOR WORKES ON FARADAYS LAW

As the South Pole moves away, the current in the winding decreases, returning to zero again when neither pole is close to the winding. While this simple generator produces AC (alternating current), the current produced is not very large since the strength of the magnetic field is not very large. The principle of electromagnetism may be used to produce a magnetic field of much greater strength. If a conductor is wound around a piece of metal, such as iron or steel, and current is passed through that conductor, a magnetic field is produced around this assembly. It is called an electromagnet.

The strength of the magnetic field produced is determined by the amount of current passing through the conductor. When a stronger magnetic field passes a winding, more current is produced in the winding. In a generator, the amount of current produced in the winding can thus be controlled by controlling the amount of current passi ng through the conductor causi ng the magnetic field. The three-phase generator is basically three separate generators in one casing. It has three completely separate windings in which current is produced, but a single rotating magnetic field. Within the generator, there is no electrical connection between the windings. The rotating magnetic field is the rotor and the windings in which current is produced are in the fixed stator.

TRANSFORMER WORKING

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 I2R 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 basic 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 operates 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 losses.