# Difference Between Star and Delta Connection

This article describes the most prominent differences between the star and delta connection and their basic introduction.

Electric circuits can be divided into the following two types.

• Single-phase AC circuit
• Three-phase AC circuit

Single-phase AC circuits transmit power and current in one phase across a single wire. While three-phase circuits produce and transmit power in three phases each phase having a phase shift of 120 degrees from each other.

Three-phase circuits are further subdivided into two kinds of connection namely –

• Star connection circuit
• Delta connection circuit

## What is Star Connection?

Star connection is a type of electrical connection of a three-phase AC circuit, comprised of four conducting wires. Three of the four wires are carrying each of the three-phase currents and the fourth wire is the neutral wire.

The three-phase wires carry the line currents at a phase difference of 120 degrees each. A star connection is the most preferred type of three-phase circuit connection for transmitting power and current over long distances, due to the presence of the neutral wire in the star connection.

The neutral wire is used to safeguard the electrical equipment such as the transformers from over-current and over-voltage flow across it.

The star circuit connection can either be balanced or unbalanced. In the balanced condition of the star connection, the same magnitude of current flows through each of the three-phase wires, and the current flowing across the neutral wire is zero.

Thus, the star-connected circuit is said to be balanced, and this balanced flow of current is the desired condition in a three-phase power system, to ensure the safety of the electric equipment connected to it.

On the other hand, an unbalanced condition of the star-connected circuit is achieved when uneven current flows across the three-phase wires. In this scenario, the neutral wire comes into action. In the unbalanced condition, the neutral wire carries the unbalanced current and passes it to the ground, thus protecting the electrical equipment connected to the supply system.

Thus, the neutral wire plays a crucial role in converting the unbalanced current flow in the three-phase system to a balanced current flow, which would otherwise be harmful to the connected electrical and electronic equipment.

Figure 1 shows the star-connected circuit. The relation between the three-phase line voltage and phase voltage, and the line current and phase current is given below.

The line voltage is equal to √3 times the phase voltage or neutral voltage as shown in equation 1. While the phase current and line current remain the same as shown in equation 2.

## What is a Delta Circuit Connection?

Delta connection is a type of three-phase circuit connection comprised of only three conducting wires carrying three-phase currents without a neutral wire. The three-phase wires are connected in the form of a delta. The delta connection is also called the mesh connection.

Due to the absence of a neutral wire in the delta connection, there persists an unavoidable unbalanced current flow in the phases of the circuit. That is why a delta circuit connection is used in three-phase systems requiring short-distance transmission of power and current.

Figure 2 depicts the three-phase representation of three phase delta circuit connection.

In the case of a delta circuit connection, the line current of each phase of the three phases is equal to √3 times the phase as shown in equation 3. While the line voltage and phase voltage are equal in magnitude as shown in equation 4.

## Difference Between Star and Delta Connection

The table below highlights the important differences between the three-phase star connection and delta connection of electronic circuits –

### Conclusion

In conclusion, this article discusses the differences between star and delta connections used in the transmission and distribution of power. The main difference between the two of these types of connections is that the star-connected systems achieve a balanced condition due to the presence of a neutral wire that carries the unbalanced current to the ground, while the delta-connected systems are mostly unbalanced systems due to the absence of a neutral connection.

Therefore, for this reason, star connections are used to transmit three-phase AC power over long distances, while delta connections are used to distribute three-phase AC power over short distances.