What Is Star Connection And Delta Connection?

What is Star Connection and Delta Connection? | How is the star connection and delta connection done?

The 3 Phase Winding connection is done in a specific way to make the 3 Phase Supply System more efficient. That connection is called the internal connection of the 3 Phase. For the transmission, distribution and utilization of 3 phase power, 3 phase internal connection is very important.

Star Delta connection Diagram

Star Delta connection Diagram


This internal connection is made by Star & Delta  in these two ways.

Star Connection

This connection is called Star Connection or (Y) Connection. As shown in the figure, U1, V1, W1 or U2, V2, W2 starting from the 6 terminals of 3 Phase Winding, all three terminals of any one of these 2 groups are shorted together. The remaining 3 terminals are outfitted for supply.

Star Point Of Star Connection

 Properties of Star Connection

The group which is shortened together, their shortened point is called the Star Point of Star Connection. Neutral wire is drawn from this star point.

Properties Of Star Connection

  • Star Connection has the same phase current and line current. (IL = Iph) because due to Star Connection, the current flowing through any of the 2 phase windings is the same.
  • The line voltage is √3 times higher than the phase voltage.
  • One of these 2 phase voltages has a phase difference of 60 ° at both the negative phase voltage (-Vph) and the other positive phase voltage (Vph).
  • The line voltage is 30 ° above the phase voltage.
  • The total power is equal to the total power of all three phases.

Formula For Total Power Of Star Connection

Formula for Total Power of Star Connection

Where Is Star Connection Used?

  • 3 Phase 4 Wire System- In Star Connection is used in 3 phase 4 wire system. The 3 Phase 4 Wire System is used for secondary distribution. It uses 3 phase wires R, Y, B and a neutral ‘N’. Neutral wire that connects to the Star Point of the Star Connection.
  • The star connection of the alternator is done in the generating stations.
  • To start Big 3 Phase Induction Moters. The use of Star Connection is pest.

Delta Connection

Delta connection diagram

Delta Connection Diagram

How Is The Delta Connection Done?

Delta connection is also called mesh connection.

As shown in the figure above, individual points of 3 Phase Winding are shorted in the delta connection. And 3 wires from the shorted ponts are taken out for spay. Meaning U, V, W in 3 phase windings of U2 V1, V2 W1, W2 U1 like this or

U1 V2, V1 W2, W1 U2 The points are thus shortened. And 3 wires are supplied to the supply from the shortened points. This is how the delta connection is made.

Properties Of Delta Connection

  • In this connection, each phase winding has parallel phases of 2 phase, due to which the phase voltage and line voltage are the same.
  • The line current is √3 times higher than the phase current.

What Is The Difference Between A Star And A Delta Connection?

Star Connection

Delta Connection

  1. Line current = phase current
1. Line current = √3 × phase current
  1. Line voltage = √3 phase voltage
2. Line Voltage = Phase Voltage
  1. Total power = √3 × VL × IL × power factor
3. Total power = √3 × VL × IL × powerfactor
  1. Phase voltage is √3 times less than the line voltage due to which number of turns it takes to winding is less. This saves copper.
4.Due to the same line voltage and phase voltage, the number of turns in the winding of this connection is high.
  1. Neutral is available in it.
5. Which is not neutral.
  1. Due to the availability of neutral, 2 types of voltages are available such as 240 volt phase voltage and 415 volt line voltage. Hence the lighting load on single phase and power load on 3 phase can be added on this connection.
6. Only 415 volt 3 Phase is available in this connection. For this reason, you cannot take a load of 1 single phase in it.
  1. In this the line voltage is 30 ° leading to this phase voltage.
7. In this line current it is 30 ° leading from phase current.
  1. It has a lower breakdown voltage.
8. It has a low breakdown voltage.


Leave a Comment

%d bloggers like this: