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For very high-power rectifiers the 18-pulse bridge connection is sometimes used. A 18-pulse bridge consists of three six-pulse bridge circuits connected in series or parallel, with their AC connections fed from a supply transformer that produces a 20° phase shift between the two bridges. This cancels many of the characteristic harmonics the six-pulse and twelve-pulse bridges produce and as a result the input current waveform looks much more sinusoidal than the six or twelve pulse rectifier case.
In the example every three phase source represents one of the three secondary windings of the supply transformer.
