What are delta connections,current voltage anf power in delta connections,summery of delta connection,uses/advantages of delta connection

Delta Connection

           A delta connection is a connection used in a three phase electrical system in which three elements in series form a triangle ,the supply being input and output at the three junctions.

           It is also known as 3 phase 3 wire system.It is preferably used in AC transmission.It is denoted by Δ .The other name of delta connection is Mesh connection.

              In case of Delta connection all the three coils are connected in series to form a close circuit.From each junction we take out one wire and out-going current from each junction assumed to be positive.In case of delta connection it look like a short circuit but in case of balance load the sum of all voltage should be zero.

             In the following fig. all values Current,Voltages and power for 3 phase delta connection can be shown.

fig

Line Current IL and Phase Current IPH in Delta Connection

                In Delta connection the line current is √3 times of Phase Current.

IR = IY = IB = IPH …. The phase currents

Then;

The current flowing in Line 1 would be;

IL or I1 = 2 x IPH x Cos (60°/2)

= 2 x IPH x Cos 30°

= 2 x IPH x (√3/2) …… Since Cos 30° = √3/2

IL= √3 IPH

Voltage in Delta Connection

                In case of Delta connection the line voltage is equal to the phase voltage. 

If the line voltage between;

Line 1 and Line 2 = VRY

Line 2 and Line 3 = VYB

Line 3 and Line 1 = VBR

Then, we see that VRY leads VYB by 120° and VYB leads VBR by 120°.

Let’s suppose,

VRY = VYB = VBR = VL   …………… (Line Voltage)

Then

VL = VPH

Power in Delta Connection

               In case of Delta Connection the total power is given below

Total Power = P = 3 x VPH x IPH x CosФ ….. (1)

We know that the values of Phase Current and Phase Voltage in Delta Connection;

IPH = IL /√3   ….. (From IL = √3 IPH)

VPH = VL   

Putting these values in power eq……. (1)

P = 3 x VL x ( IL/√3) x CosФ …… (IPH = IL / /√3)

P = √3 x√3 x VL x ( IL/√3) x CosФ …{ 3 = √3x√3 }

P = √3 x VLx IL x CosФ  

P = 3 x VPH x IPH x CosФ

Summary Of Delta Connections

•  In case of delta connections every wire is connected with the other two wires to form a triangle,and all the common points (Three) form the three phases.
• In case of delta connection we have 3 wire 3 phase system.
• In case of delta connection we have 3 wire 3 phase system.
• In delta connection we do not have  any neutral.
• In case of delta connection we have same line and phase voltage.
• In delta connection line current is root three times the phase current.
• As we know in case of delta connection line and phase voltage is same hence we need more insulation for each phase.
• Delta connections normally used in distribution networks.
• Due to high insulation delta connection used for shorter distance.
• total three phase power can be calculated in delta connections with the help of following.

                 P = √3 x VLx IL x CosФ

                  P = 3 x VPH x IPH x CosФ

• These types of connections are normally used in application which require high starting torque.

Uses/Advantages of Delta Connections

• One of the biggest advantages of delta connection is high reliability.If one of the three primary windings fails the secondary will still produce full voltage on all three phases.If remaining phases must be able to carry the load.
• Delta type of connections are most suitable for rotatory conveyors.
• Most of the 3-phase induction motors are delta connected.
• If we consider three phase we will find majority as delta connected.Reason for this is that in case of unbalanced load is the flexibility with which loads may be added or removed on a single phase.