What is Star Connection? Properties, Application, Diagram
In a three-phase electrical system, two types of connection are mainly used - 1. Star Connection and 2. Delta Connection. In this article, we are going to discuss about star connection. In the next article, we will discuss about the delta connection. The single-phase power system has two conductors that are phase and neutral whereas the three-phase power system has a minimum of three conductors and sometimes it also has four conductors. In the star connection, you can see sometimes three conductors or sometimes four conductors.
What is Star Connection?
In the three-phase system, where all the three-phase wires are connected to a common point. This common point is known as the neutral point. And this type of connection is known as a Star Connection. The star connection will be called a three-phase three-wire system when only three live wires are used. And the star connection will be called a three-phase four-wire system when all three phases and the neutral wire are also used. The neutral wire is connected to the neutral point where all three phases are connected. Generally, in the power system, the neutral point is connected to the ground through a neutral grounding resistor, that keeps the system balanced. As the star connection looks like the English letter 'Y', it is also known as the wye connection.
Star Connection Symbol
Here, you can see the symbol of Star Connection. It has three open ends and a junction point. These three ends for three phases and the junction point is the neutral point.
Star Connection Diagram
Here, you can see the diagram of star connection.
Properties of Star Connection
1. In the star connection, all three phases are connected to a neutral point. If the voltage across all the phases and the current in each phase are equal, the voltage of the neutral point will be zero.
2. In the star connection, the line voltage and phase voltage are different. Line voltage is root 3 times of phase voltage. Line voltage is measured between any two phases whereas phase voltage is measured between any one phase and neutral.
3. In a star connection, we can have two different voltages, so we can connect it with two different circuits operated at two different voltages. For example, from a 440V three-phase system, we can get two different voltages such as 440V and 230V.
4. In the star connection, the line current is equal to the phase current.
5. In the star connection, less insulation is required for each phase as the phase voltage is less than the line voltage.
Star Connection Formula
As the line and phase voltage are different for the star connection,
So the formula of Line voltage is,
The formula of line current in the star connection is
The formula of power in the star connection is,
Here, VL = Line Voltage
VPh = Phase Voltage
Advantages of Star Connection
1. The main advantage of a star connection over a delta connection is that a star connection provides neutral, so we can get two different voltages from the same power system.
2. As the individual phases are carrying low voltage so less insulation is required which reduces the cost.
3. In the Star connection, the line current is equal to the phase current, so low current rating protective devices can be used.
4. Star connections can be used for both low and high-voltage systems. Low voltage can be obtained from any one phase and neutral whereas high Voltage can be obtained from two phases.
5. Both three-phase three-wire and three-phase four-wire systems are possible with the star connection.
Applications and Uses of Star Connection
1. Star connection is used for both low and high-voltage transmission and distribution systems. It is mostly used for Distribution systems rather than transmission systems.
2. Even a star connection is used for the electrical power generation also. Because we know that alternator in power generation plant is always star connected.
3. Star connection is used for the starting of heavy induction motors to reduce the starting current at starting by applying the lower phase voltage.
4. Star connection is used when single-phase devices are operated by taking power from the three-phase system.
Read Also:
What is Star Connection? Properties, Application, Diagram
Reviewed by Author
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July 28, 2021
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Reviewed by Author
on
July 28, 2021
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