2. With respect to the connections, as
- a. Star;
- b. Delta;
- c. Star delta;
- d. Delta star.
The six wire system is shown in fig. 2,160. It is equivalent to three independent single phase circuits. Such arrangement would only be used in very rare instances.
Fig. 2,160.—Three phase six wire system. It is equivalent to three independent single phase circuits and would be used only in very rare cases.
Ques. How can three phase current be transmitted by three conductors?
Ans. The arrangement shown in fig. 2,160 may be resolved into three single circuits with a common or grounded return.
When the circuits are balanced the sum of the current being zero no current will flow in the return conductor, and it may be dispensed with, thus giving the ordinary star or Y connected three wire circuit, as shown in fig. 2,163. The transformation from six to three wires being shown in figs. 2,161 to 2,163.