Construction and operation of transformers
A transformer is a device used to change the properties of the flowing current (i.e. the voltage value, but also the input electrical intensity to the required output value). It is also an energy transforming equipment, among other things, used to change the voltage between subsequent stages of electricity transmission. These devices are worth taking a closer look at. How a transformer is constructed and how it works?
Safe energy transfer
A transformer is a basic component that transfers energy from one electrical circuit to another. Energy is transferred via a magnetic field between two windings that are close to each other. The circuits between which energy is transferred are separated from each other and the windings are insulated. This allows the transformers to operate safely, preventing the possibility of electric shock to the user.
What is the structure of a transformer?
The main parts of the transformer’s construction are a steel, ferromagnetic core and two windings placed close to each other, called primary and secondary. They can be made of aluminium or copper insulated wires. The core is a magnetic circuit and conducts magnetic flux. It consists of columns connected by yokes on which the winding is wound. The core is made of thin insulated sheets saturated with silicon. This makes it possible to reduce losses resulting from eddy currents.
Energy transferred by a magnetic field
Typically, the winding is used in the form of concentric cylinders mounted on one column. The lower winding is mounted directly on the column, while the upper winding is created on the lower one. The construction of the transformer allows for maintaining the insulation of the column and the insulation between the windings themselves, which are galvanically separated. Therefore, there is no electrical connection between them and energy is transferred via a magnetic field.
How does a transformer work and what does it affect?
Changing the properties of electrical energy requires its supply to the transformer windings. The primary winding is connected to a current source, which results in energy flow and the creation of an alternating magnetic field. The transformer core conducts an alternating magnetic field that flows through the secondary winding. This operation of the transformer, i.e. a change in the secondary winding, causes electromagnetic induction and a variable electromotive force. Energy is transformed in this way, and the level of its change depends on the number of turns the windings have.
Step-down and step-up transformers
If the number of turns in the primary winding is greater than that of the secondary winding, the induced voltage will be lower than the primary voltage. Such a device is referred to as a step-down transformer. In the opposite situation, the secondary voltage is higher than the primary one and it is a step-up transformer. In some cases, autotransformers are also used, in which a single winding serves as both windings. Such equipment is used, among others, in the power energy industry.
Power transformers
Power transformers are the largest devices in terms of dimensions and power transfer capabilities. They are installations connecting various nodes of the power system, which operate at different voltage levels. In Poland, three-phase transformers are used, which have three windings on the core for each circuit – lower and upper. These windings can be connected in the form of a triangle, an insulated star or a grounded star.
Effective delivery of energy to consumers
Voltage conversion in the power energy system is also performed to reduce transmission losses on power lines. Additionally, phase shifters are used, i.e. transformers that allow the adjustment of the phase shift in order to change the active and reactive power flows. The operation of the transformer allows you to connect highest voltage networks (400 kV and 220 kV), high voltage networks (110 kV), medium voltage networks (6, 10, 15 and 20 kV) and low voltage networks (0.23 and 0.4 kV).
Transformers are used to change the voltage value of the current. These devices are placed at all stages of the transmission network. In the power industry, they are used to distribute energy and transport it on lines with lower voltages. In this way, energy can be efficiently delivered to end users.