Delta Connection In Three Phase System-Advantages

In the Delta connection, the dissimilar terminals of three phase windings are connected together. The finishing end of one phase is joined to the starting end of the other phase to obtain mesh or delta-connected winding. 

Delta connection in power system is shown in the below diagram 


As shown in the diagram of the three-phase Δ-connected motor, the three line conductors are brought from the three junctions of the delta and named R(U1&W2), Y (U2&V2), and B(W1&V1), and this connection is called a three-phase three-wire delta connected system. 

the delta connection is also called a mesh connection because it forms a closed circuit. 

This connection looks like the Greek letter Δ hence named as delta connection. 

In Δ connection, only three phase three-wire system can be formed no neutral exists in delta connection. 

In delta connected system only one phase is included between R&Y, Y&B, R&B any two lines hence magnitude of voltage between two-line voltages is equal to the phase voltage in a delta or mesh-connected system. 

And the current flowing through phases is 

 IL= √3 IPH

Three line currents are equal in magnitude and displaced by 120 degree from each other. 

Voltage in balance delta connected system

Relation between line voltage and phase voltage 

As the system is balanced hence three-phase voltages are equal in magnitude and displaced by 120 degree apart from each other from the diagram of delta connection we can see that only one phase winding is included between any pair of lines hence phase voltage is equal to line voltage for mesh connection. 


Relation between line current and phase current 

As said, the above system is balanced the three currents flowing through the system are IR, IY, and IB are equal in magnitude and displaced by 120 degree. 

Current in line 1 is  I1 = IR – IB

Current in line 2  is I2 = IY – IR

Current in line 3 is I3 = IB – IY

Line current IL= √3  Iph

Power in Delta Connection

the power of each phase
Power / Phase = VPH x IPH x CosФ
the values of Phase Current and Phase Voltage in Δ Connection

IPH = IL /√3   ….. (From IL = √3 IPH)

VPH = VL  

Putting these values in power in  VPH x IPH x CosФ

P = 3 x VL x ( IL/√3) x CosФ  

P = √3 x√3 x VL x ( IL/√3) x CosФ 

P = √3 x VLx IL x CosФ 

Hence proved;

Power in Δ Connection,

P = 3 x VPH x IPH x CosФ …. or

P = √3 x VL x IL x CosФ

Advantages of delta connection

  • This type of connection is most suitable for rotary conveyer
  • The majority of 3 phase loads are delta connected rather than star connection
  • Most three phase induction motors are delta connected

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