3-Phase Transformer Connection

There are Different Connections used in 3-phase transformers to connect their windings Including

Method of Three phase transformer connection

Star-Star or Y-Y Connection
Delta-Delta or Δ-Δ Connection
Star-Delta or Y-Δ Connection
Delta-Star or Δ-Y Connection

Star-Star Connection(Y-Y)

Star-Star is a type of Three-phase winding connection in which both primary and Secondary windings are connected in a Star connection. Star-star connections work better on the balance load. In this type of Connection, Both Sides of the Neutral are on Earth. Star-Star Connection is Suitable For Low Current and High Voltage Transformers. The line current and phase current are equal in the star-star connection. The Other Name of Star-Star Connection is called Y-Y Connection.

3-Phase Transformer Connection

Advantages of Star-Star Connection

We need a smaller number of Turns because Voltage is Reduced by 1/√3 so Copper Saving is possible.
We need less space due to the less insulation Required.
There is No phase Displacement In primary and Secondary Windings so we can easily operate transformers in parallel.
We obtain 3 Phase 4 wire Systems in star-star connection.

Disadvantages of Star-Star Connection

if we do not connect the primary neutral to the source, unbalanced conditions happen so the result is neutral floating.
The transformer obtained a Third harmonic magnetic Current so the result is distorted EMF is produced if we do not connect the primary neutral to the generator neutral.

Delta-Delta Connection(Δ-Δ)

Delta-Delta Connection is a three-phase winding connection in which both primary and secondary windings are in the delta connection. This connection is mostly suitable for low voltages. The Line voltages and phase voltages are equal in the Delta-Delta connection. The Relation between phase current and line current is

3-Phase Transformer Connection

Ip=IL/√3

This System is used where we require low voltage and high current.

Advantages of Delta-Delta Connection

In the Delta-Delta connection phase, the current is reduced by 1/√3 of the line current so the cross-sectional area is reduced and conductor saving is possible.
The third harmonic is easily passed in the Delta-Delta Connection so we obtained sinusoidal voltages.
Imbalance load is Not affecting the Delta-Delta connection.
There is no phase Displacement in primary and secondary windings.
if one phase is not provided supply the other is operated in a full load of 57.7%.

Disadvantages of Delta-Delta Connection

In the Delta-Delta connection, there are no neutral wires so we did not obtain a three-phase 4-wire system.
we need a high value of insulation because line voltage is equal to phase voltage.

Star-Delta Connection(Y-Δ)

Star-Delta is a Three phase winding connection in which primary winding is connected to the star and secondary winding is connected to the delta connection. Star-Delta connections are mostly used in substations end of transmission lines where we step done the voltage. In this connection, we connect primarily to neutral earth. The Transformation ratio of Secondary and primary line voltage is 1/√3 times. The phase Displacement from Primary to secondary is 30૦.

3-Phase Transformer Connection

Advantages of Star-Delta Connection

Disadvantages of Star-Delta Connection

Delta-Star

Delta-Star Is a type of three-phase connection in which primary winding is connected in delta and secondary winding is connected in star connection. Delta-Star connections are mostly used where we need to step up the voltage for example H.T. Transmission system. Delta-Star connections are most frequently used because we operate an A 3- 3-phase lighting circuit.