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A single-phase full-wave half-controlled bridge converter feeds an inductive load. The two SCRs in the converter are connected to a common DC bus. The converter has to have a freewheeling diode

1. because the converter inherently does not provide free-wheeling
2. because the converter does not provide free-wheeling for high values of triggering angles
3. or else the free-wheeling action of the converter will cause shorting of the AC supply
4. or else if a gate pulse to one of the SCRs is missed, it will subsequently cause a high load current in the other SCR

Correct answer: because the converter does not provide free-wheeling for high values of triggering angles

Solution

In a half-controlled bridge feeding an inductive load, the freewheeling diode allows the load current to continue when the source is not conducting. This becomes necessary especially at higher firing angles, when the converter would otherwise fail to provide a current path.

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