Difference Between Star and Delta Connection

Last Updated : 06 Oct, 2023

Electric circuits are divided into types i.e. Single-phase AC circuits and Three-phase AC circuits. A circuit that transmits the power and current in one phase only and across a single wire is known as a single-phase AC circuit. Three-phase AC circuits transmit power in three phases. The three-phase circuit at least has 3 wires or conductors that carry AC voltage. These three-phase AC circuits are divided into star and delta connection circuits. Both circuits differ from each other concerning some parameters. Let’s study the difference in detail.

Star Connection

Star connection is one type of three-phase AC circuit. Star connection is denoted by ‘Y’. The star connection consists of four wires out of which three wires are phase wires that carry current and one is the neutral wire. This neutral wire helps to prevent electrical equipment from overcurrent and voltage. Star connection can be implemented using three wires or four wires. If only three phase wires are used then it is known as 3 phase 3 wire system. If three-phase wires and one neutral wire are used it is known as a Three-phase four-wire system.

Star Connection

Advantages of Star Connection

Star connection requires less insulation and less number of turns.
As neutral wire is used in star connection, it is suitable for both three-phase and four-phase systems.
In the star connection, there is no phase shifting for primary and secondary voltage.
The neutral point of the star connection can be earthed.
The phase voltage VP is given by $V_{P} = \frac{V_{L}}{\sqrt3}$ .
A star connected alternator will require fewer turns than a delta connected alternator for the same voltage because the induced emf in the primary winding of an alternator is directly proportional to the number of turns.

Disadvantages of Star Connection

Dependency on Neutral Conductor: The neutral conductor plays a critical role in maintaining balanced voltages. Failure of the neutral conductor can lead to unbalanced voltages and potential damage to the system.
Neutral Current: The neutral conductor carries the return currents from the loads. Unbalanced loads may result in significant neutral currents.
Higher Cost: Implementing a star connection requires additional wiring and a neutral conductor, increasing installation and maintenance costs.

Applications of Star Connection

Power Distribution: The star connection is widely used in electrical power distribution systems, where it enables efficient power distribution to multiple loads. It simplifies the wiring and allows for individual control of loads connected to different phases.

Industrial Motors: Three-phase induction motors are commonly connected in a star configuration. The star connection provides a balanced supply voltage and allows for high starting torque while reducing the current and voltage stress on the motor windings.

Power Generation: Many electrical generators, such as alternators or synchronous generators, are connected in a star configuration. It allows for a neutral point to be established, which is essential for grounding and balancing the load currents.

Delta Connection

Delta connection is another type of three-phase AC circuit. Delta connection is denoted by ‘∆’. Delta connection is also known as mesh connection. Delta connection consists of only three phase wires. The neutral wire is not used in the delta connection. Delta connection is also known as mesh connection. As the neutral wire is not used in a delta connection it cannot prevent the circuit from over-current. Therefore delta connection is mostly used for applications at short distances and for distributed networks.

Delta Connection

Formula for conversion from delta to Star connection:

Star= $\frac{V_{L}}{\sqrt3}$

Where VL is line to line voltage in delta connection and star is line to line voltage in star connection.

Advantages of Delta Connection

The overall construction cost required for a delta connection is low.
The design of the motor using a delta connection is easy.
Delta connection requires less power.
Delta connection provides more torque as compared to the Star connection.
Most of the three phase loads are connected using Delta Connection because in the case of unbalanced load, flexibility is there to add or remove the loads on a single phase. It is difficult to do with star 3-wire load.

Disadvantages of Delta Connection

The Delta connections lack a neutral point, which can make grounding and fault detection more complex.
In delta connection detection of faults under the earth’s surface is difficult.
The Delta connections may result in higher phase currents compared to star connections.

Applications of Delta Connection

High-Power Transmission: The Delta connections are commonly used in the high-power transmission and distribution networks due to their ability to handle high currents efficiently.

Motor Applications: The Delta connections are employed in the industrial motors as they provide a simpler and cost-effective solution for the driving three-phase motors.

Electric Generators: The Many generators are configured in the delta connection as it offers better insulation and more compact than a star connection.

Transformers: The Delta configurations are often used in the transformers. It is used to step up or step down voltage levels.