In many high-powered applications, three-phase voltages need to be rectified to give rise to a single DC supply; such rectification can be accomplished using an extension of the bridge rectifier such as the three-phase diode bridge rectifier.
Let’s consider the balanced three-phase circuit shown in Figure 1.0 below; the three-phase wye-connected source is connected to a resistive load by means of a three-phase transformer, with a delta-connected primary and a wye-connected secondary. The circuit may also operate without the transformer.
The three secondary currents i.e. ia, ib, and ic, flow through pairs of diodes D1 to D6 in a way very similar to the single-phase rectifier. The diodes will conduct in pairs depending on the relative line voltages, according to the following sequence: D1-D2, D2-D3, D3-D4, D4-D5, D5-D6 and D6-D1.
The line-to-line voltage in a three-phase wye-connected source is √3 times the phase voltage. The instantaneous source voltages and the related diode conduction periods, in addition to the load voltage are shown in the Figure 1.1.
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