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| Fig. 6.7. (a) Single-phase two-pulse bridge converter and (b) Three-phase six-pulse bridge converter |
There is a large variety of SCR controlled converters (or rectifiers). One way of classifying these ac to dc converters is accroding to the number of supply phases on the input side. As per this classification, the ac to dc converters discussed in Figs. 6.1 to 6,4 are single-phase half-wave converters. Three-phase controlled rectifiers, as the name suggests, have three- phase supply on their input side, these are discussed later in this chapter. The other way of classification is according to the number of load current pulses per cycle of source voltage. It is seen from Art. 6.1 that single-phase half-wave controlled rectifiers produce only one pulse of load current during one cycle of source voltage, these can therefore be termed as single-phase one-pulse converters. Thus, the controlled rectifiers discussed in Figs. 6.1 to 6.4 are all single- phase one-pulse converters.
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| Fig. 6.6. (a) Single-phase two-pulse mid-point converter and (b) three-phase six-pulse mid-point converter The disadvantages of single-phase half-wave, or single-phase one-pulse minimised by the use of single-phase full wave, or single-phase two pulse, practice, there are two basic configurations for full-wave controlled co configuration uses an input transformer with two windings for each input F This is called mid-point converter. A single-phase two-pulse mid-point SCR conv in Fig. 6.6 (a) and a three-phase 6 pulse mid-point converter in Fig. 6.6 (6). |
The second configuration uses SCRs in the form of a bridge circuit. Single-phase full-wave. or two-pulse, bridge converter using four SCRs is shown in Fig. 6.7 (a) and a three-phase six- pulse bridge converter using six SCRs in Fig. 6.7 (b). A bridge converter has some advantages over mid-point converter, these will be discussed after both these configurations are studied in the next article.