The wye connected secondary allows single phase load to be distributed among the three phases to neutral instead of being placed all on one winding as with a four wire delta secondary. As in the balanced system the three phase current i 12 i 23 and i 31 are equal in magnitude but are displaced from one another by 120 electrical.

Analysing Three Phase Circuits
3 phase delta connection diagram. Three phase three wire δ connection has no common. It is used when both single and three phase power is desired to be supplied from a three phase transformer or transformer bank. The phasor diagram of the y connection of the three phase transformer is shown in the figure. Another configuration is known as the delta for its geometric resemblance to the greek letter of the same name δ. One disadvantage of delta connected three phase transformers is that each transformer must be wound for the full line voltage in our example above 100v and for. Delta or mesh connection δ system is also known as three phase three wire system 3 phase 3 wire and it is the most preferred system for ac power transmission while for distribution star connection is generally used.
A three wire three phase circuit is usually more economical than an equivalent two wire. High leg delta also known as wild leg stinger leg bastard leg high leg orange leg red leg dog leg delta is a type of electrical service connection for three phase electric power installations. Hence in delta connection line voltage is equal to phase voltage. The phasor diagram is shown below. A three phase transformer is built for a specific connection and voltage transformation and the unit will have a nameplate with the internal connections shown. When a single unit or bank of three is used there are four types of connections.
The primary line voltage is equal to the secondary phase voltage. Relation between phase current and line current in delta connection. Take close notice of the polarity for each winding in the figure below. The relation between the secondary voltages is v ls 3 v ps. Three phase electric power is a common method of alternating current electric power generation transmission and distribution. The deltawye connection is the most commonly used three phase transformer connection.
The first symbol indicates the connection of the primary and the second symbol is the. Y y y y and. In a delta connected dd group of transformers the line voltage v l is equal to the supply voltage v l v sbut the current in each phase winding is given as. 1 3 i l of the line current where i l is the line current. It is also used to power large motors and other heavy loads. It is a type of polyphase system and is the most common method used by electrical grids worldwide to transfer power.
The y connection of the three winding transformer is shown in the figure below. The four basic connections are.