Fig. 1,560.—Diagram showing determination of path and value of current flowing in delta connected armature.
Ques. Since most three phase windings can be connected either Y or delta, what should be noted as to the effects produced?
Ans. With the same winding, the delta connection will stand 1.732 as much current as the Y connection, but will give only 1 ÷ 1.732 or .577 as much voltage.
Fig. 1,561.—Triumph brushes and brush holder. The holder is of the box type provided with an adjustable tension spring, making the brushes self-feeding. Each holder is carried on insulated studs attached to a cast iron yoke which is mounted on the bearing.
Fig. 1,562.—Diagram of Y connection with a common return wire. When the three lines leading from a, b and c are equal in resistance and reactance, or in other words when the system is balanced, the currents of the three phases are equal and are 120° apart in phase (each current lagging behind its pressure by the same amount as the others) and their sum is at each instant equal to zero. In this case the resultant current being equal to zero there is no need of a common return wire. However, in some cases, where power is distributed from transformers or three wire systems, the different branches are liable to become unbalanced. Under such circumstances the common return wire is sometimes used, being made large enough to take care of the maximum unbalancing that may occur in operation. The return wire is used sometimes on alternators that furnish current mostly for lighting work.