The supply system which has only two phases is known as two phase supply system. In this case there are two sets of windings which are placed at 90 to each other. The four ends are taken out and connected to the slip rings. The ends or terminals of the windings are connected in the following manner:
(a) Two four wire supply system. In this case four wires are taken out from the four slip rings. Two wires from each phase are connected with two separate circuits as shown in Fig. 16.1.
(b) Two phase three wire system. In this case two ends are connected together and only three wires are taken out as shown in Fig. 16.2. The line and phase voltages are taken from the different terminals. The line voltage is obtained from the two outer ends and the phase voltage between the middle wire and either of the outers. These both voltages are at right angle to each other.