The star connection is a frequently used connection type in electrical engineering, especially for three-phase applications. It is characterized by a star-shaped arrangement of the phases, in which the loads are connected to a common point, the so-called neutral conductor. This electrical circuit enables a stable distribution of voltage, current and power and is often used in power distribution and transformers.
In the star connection, three phase conductors are each connected to one end of a load. The other ends of all three loads are brought together at the common neutral conductor, also known as the star point. This results in a star-shaped topology. Each load is located between a phase conductor and the neutral conductor. The voltages applied to these loads are referred to as phase voltages.
Between two outer conductors there is the so-called conductor voltage, which is greater than the phase voltage. The following relationship applies:
UL=3â‹…USU_L = sqrt{3} cdot U_SUL=3â‹…US
ULU_LUL stands for the conductor voltage and USU_SUS for the phase voltage. The symbol “cdot” stands for the multiplication. In a symmetrical star connection, the phase voltages are equal, as are the phase currents, if the resistances of the individual loads are identical.
In addition to the star connection, there is also the delta connection, in which the loads are connected in the form of a closed triangle. In contrast to the star connection, the connection points of the loads are connected directly to each other, creating a triangle. Both types of connection are used in electrical circuits such as electric motors or transformers.
An important difference lies in the applied voltages and currents. In the delta connection, the phase voltage corresponds to the voltage at the load, whereas in the star connection, the phase voltage is applied to the load. With identical resistance per phase, the phase currents in the star connection are equal to the phase conductor currents.
The voltages, currents and resistances in the star connection can be easily calculated. With the same load – i.e. the same resistances in all phases – the currents are the same. In this case, we speak of a symmetrical load. The current in the neutral conductor is then zero, as the currents cancel each other out.
The level of the current depends on the respective resistance through which it flows. The lower the resistance, the higher the current. The value of the resistors in the individual strings is decisive for the current distribution in the grid.
The star connection plays a central role in the transformation of electrical energy. In energy supply, it is often used in conjunction with transformers to transport electrical energy efficiently over long distances. The star connection is particularly advantageous, as the same voltages can be realized for consumers and different voltage levels can be provided.
The combination of star and delta connection allows motors to be operated initially in star (lower current consumption) when starting up and later in delta (full torque). Such solutions are typical for industrial use with three-phase current.
The most important content relating to the star connection includes the structure with phase conductors, neutral conductors, resistors and the calculation of voltages and currents. The star connection offers a stable and safe way of distributing energy under the same connection conditions.
Due to its versatility, it is used in both industrial and private networks and represents one of the most important fundamentals in electrical engineering. Its applications range from simple electrical circuits to complex transformation systems.
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