A transformer is a static electromagnetic device that is designed to convert (transform) an alternating voltage by increasing or decreasing it. It can also be used to change the number of phases and less often to change the frequency of alternating current.
Electrical energy is usually transmitted over long distances at a voltage that is several times higher than the voltage level used by domestic consumers. The use of transformers provides an improvement in the quality of the process of transmission of electrical energy and allows to reduce losses occurring in networks.
Device and principle of operation
A transformer structurally consists of two (or more) windings and a core, which is also called a magnetic circuit. The voltage is applied to the device on the primary winding, and the already converted voltage is removed from the secondary winding. The windings are connected to each other by an alternating magnetic field, which is created in the core by the voltage supplied to the primary winding.
Types of transformers
- power;
- measuring;
- low power;
- pulse;
- peak transformers.
Losses
The transmission of electricity from the primary to the secondary is invariably accompanied by losses.
There are no rotating components in the transformer and therefore no mechanical losses. However, in the unit, losses occur in the copper of the windings due to the presence in the windings of an electric resistance, as well as magnetic losses in the steel of the core due to the resulting eddy currents and magnetization reversal.
For these reasons, not all energy is transferred, but only most of it.
Efficiency and ways to increase it
Like any other energy converter, a transformer has a coefficient of performance (COP), which characterizes the efficiency of its operation.
Efficiency is the ratio of the power that the unit's payload draws to the power that the loaded transformer draws from the grid. Also, the efficiency can be expressed in terms of the ratio of the energy efficiently used to the energy consumed from the system.
Since the transformer is a passive energy converter, its efficiency is always less than unity (η <1). This means that the power consumed by the load connected to the secondary winding is always less than the power consumed by the loaded device from the system.
There are a number of ways to improve efficiency, primarily aimed at reducing losses. For example, to reduce losses in copper, it is necessary to increase the cross-section of the winding wires. And a decrease in losses due to magnetization reversal can be achieved when using soft magnetic steel with a certain composition and structure for the core.
To reduce eddy current losses, the magnetic core should be collected from separate, isolated from each other steel bars. Also, silicon can be used as an additive in the material of the magnetic circuit.