The Rectifier reference article from the English Wikipedia on 24-Jul-2004 (provided by Fixed Reference: snapshots of Wikipedia from wikipedia.org)

Rectifier

A rectifier is one or more diodes arranged for converting alternating current (AC) to direct current (DC).

When just one diode is used to rectify AC (by omitting the negative going portion of the waveform) the difference between the term diode and the term rectifier is merely one of usage, e.g. a rectifier depicts a diode that is for being used to convert AC to DC.

However, almost all rectifiers comprise a plurality of diodes in a specific arrangement for more efficiently converting AC to DC than is possible with just a single diode.

Full wave rectifiers negate the negative portions of the alternating current waveform. The positive portions thus combine with the negated negative portions to produce a wholly positive result.

For single phase AC, if the AC is center-tapped, then two diodes back-to-back (i.e. anodes-to-anode or cathode-to-cathode) form a full wave bridge rectifier. If there is no center tap, then four diodes, arranged in a bridge, are needed.

For three phase AC, six diodes are used. Typically there are three pairs of diodes, each pair though, not being the same kind of double diode that would be used for a full wave single phase split supply. Instead the pairs are in series (anode to cathode). Typically the double diodes have four terminals so the end user can configure either as single phase split supply use, or for half a bridge or three phase use.

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