Ans. In three phase star grouping, one end of each of the three circuits is brought to a common junction M, usually insulated, and the three other ends are connected to three terminals a, b, c, as shown in fig. 1,546, or in the case of revolving armatures to three slip rings.
Fig. 1,546.—Diagram of three phase star grouping, commonly called Y grouping owing to its resemblance of the letter Y. The current in each main is obviously equal to the current in each phase winding, but the terminal pressure is the vector sum of the pressures in the component phase windings, that is, √3 multiplied by the pressure in one phase.
Ques. What other name is given to this connection, and why?
Ans. It is commonly called a Y connection or grouping owing to the resemblance of its diagrammatic representation to the letter Y.
Fig. 1,547.—Radial diagram of three phase, one slot winding with Y connection.
Fig. 1,548.—Radial diagram of three phase one slot winding with delta connection.