SOLUTION

Six phases half-wave rectifier or 3 Phase Full Wave Rectifier

In three-phase full-wave rectifier, six diodes are used. It is also called 6-diode half-wave rectifier. In this, each diode conducts for 1/6^th part of the AC cycle. The three-phase full-wave circuit is often used instead of the three-phase halfwave when less ripple is required and the static magnetization of the transformer core is to be avoided.

The six-phase voltages can be obtained in the secondary by using a center-tapped arrangement on a Star-connected three-phase winding and the vector diagram of six-phase voltages is shown in Fig. There are six diodes in a six-phase rectifier. When a particular phase voltage is higher than other phases, diodes on the particular phase conducts. This rectifier circuit is also called a three-phase midpoint six-pulse rectifier.

Each diode conducts for π/3 or 60° duration. Current flows through one diode at a time. Therefore, the average current is low but the ratio between maximum current to the average current in the diodes is high. Hence the utilization of transformer secondary is poor. The dc currents in the secondary of the six-phase Star rectifier can be canceled in the secondary windings and core saturation is not encountered.

The ripple frequency of a six-phase half-wave rectifier is a six-time supply frequency.

Since the Supply frequency is 60 Hz, therefore, the ripple frequency is 6 × 60 Hz = 360 Hz