What is Delta connection in Three Phase Power System

What is Delta connection?

Delta connection is an arrangement of three of same or different passive components. It is also called a mesh connection. The three passive element is connected with each other; the input supply is given through the two junctions of the element. Or the starting ends of the three phases or coils are connected to the finishing ends of the coil. Refer the drawing.

What is Delta connection in Three Phase Power System

In Delta connection, the three windings interconnection looks like a short circuit, but this is not true if the system is balanced, then the value of the algebraic sum of all voltages around the mesh is zero (from Kirchhoff’s voltage rule).

In delta connection, there is three wires alone and no neutral terminal is taken. Normally delta connection is preferred for short distance due to the problem of unbalanced current in the circuit.

The relationship between line and phase measurement:

What is Delta connection in Three Phase Power System
In delta connection, the line voltage is same as that of phase voltage. And the line current is √3 times of phase current.

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Net power transfer in the three-phase system P is

What is Delta connection in Three Phase Power System

Power is an independent quantity of the circuit arrangement of the three-phase system. The net power in the circuit will be same in phase and line.


Advantage of Delta connection:

  • Delta connection is preferred where the equipment needs high running torque. Because of torque is directly proportional to the square of the voltage so to have better performance of induction motor it needed to be connected in delta. So normally star delta starter is used in the induction motor.
  • Size of the conductor is less as the phase current decreases by increasing the phase voltage of the machine. Please see the current relation of both line and phase.

Disadvantage of delta connection:

  • High winding insulation requirement as the voltage increases, that’s why high voltage transformer is not preferred in star winding
  • System stability, delta configuration does not have neutral connection, during abnormal condition fault current remains in the system until to get a path. Due to this reason, the system may damage physically.
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