Difference between Star (Y or Wye) and Delta (Δ) Connection

Star Connection (Y or Wye)

Delta Connection (Δ)

A Star Connection is a 4 – wire connection (4th wire is optional in some cases)

A Delta Connection is a 3 – wire connection.

Two types of Star Connection systems are possible: 4 – wire 3 – phase system and 3 – wire 3 phase system.

In Delta Connection, only 3 – wire 3 phase system is possible.

Out of the 4 wires, 3 wires are the phases and 1 wire is the neutral (which is the common point of the 3 wires).

All the 3 wires are phases in a Delta Connection.

In a Star Connection, one end of all the three wires are connected to a common point in the shape of Y, such that all the three open ends of the three wires form the three phases and the common point forms the neutral.

In a Delta Connection, every wire is connected to two adjacent wires in the form of a triangle (Δ) and all the three common points of the connection form the three phases.

The Common point of the Star Connection is called Neutral or Star Point.

There is no neutral in Delta Connection

Line Voltage (voltage between any two phases) and Phase Voltage (voltage between any of the phase and neutral) is different.

Line Voltage and Phase Voltage are same.

Line Voltage is root three times phase voltage i.e. VL = √3 VP. Here, VL is Line Voltage and VP is Phase Voltage.

Line Voltage is equal to Phase Voltage i.e. VL = VP.

With a Star Connection, you can use two different voltages as VL and VP are different. For example, in a 230V/400V system, the voltage between any of the phase wire and neutral wire is 230V and the voltage between any two phases is 400V.

In a Delta Connection, we get only a single voltage magnitude.

Line Current and Phase Current are same.

Line current is root three times the phase current.

In Star Connection, IL = IP. Here, IL is line current and IP is phase current.

In Delta connection, IL = √3 IP

Total three phase Power in a Star Connection can be calculated using the following formulae.

P = 3 x VP x IP x Cos(Φ) or

P = √3 x VL x IL x Cos(Φ)

Total three phase Power in a Delta Connection can be calculated using the following formulae.

P = 3 x VP x IP x Cos(Φ) or

P = √3 x VL x IL x Cos(Φ)

Since Line Voltage and Phase Voltage are different (VL = √3 VP), the insulation required for each phase is less in a Star Connection.

In a Delta Connection, the Line and Phase Voltages are same and hence, more insulation is required for individual phases.

Usually, Star Connection is used in both transmission and distribution networks (with either single phase supply or three – phase.

Delta Connection is generally used in distribution networks.

Since insulation required is less, Star Connection can be used for long distances.

Delta Connections are used for shorter distances.

Star Connections are often used in application which require less starting current

Delta Connections are often used in applications which require high starting torque.