Single phase half bridge converter working help

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Discussion Overview

The discussion revolves around the operational differences between using diodes and silicon-controlled rectifiers (SCRs) in a single phase half bridge converter, particularly focusing on the implications for circuit behavior and load types.

Discussion Character

  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions the necessity of using diodes instead of SCRs in a half bridge converter, suggesting that firing SCRs simultaneously with other switches could yield similar operation.
  • Another participant notes that while SCRs might work for resistive loads, they could present issues with highly reactive loads, indicating a need for further examination of the circuit design.
  • A different viewpoint suggests that using all four SCRs could lead to a negative voltage output before certain switches are triggered, raising concerns about circuit behavior.
  • One participant acknowledges that the introduction of diodes creates a freewheeling path, which addresses their initial confusion regarding the circuit operation.

Areas of Agreement / Disagreement

Participants express differing opinions on the use of diodes versus SCRs, with no consensus reached on the best approach for all load types. The discussion remains unresolved regarding the implications of using SCRs in various scenarios.

Contextual Notes

Considerations regarding load types (resistive vs. reactive) and the behavior of SCRs in the circuit are mentioned but not fully explored, leaving some assumptions unaddressed.

electricallov
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why are we using two diodes instead of two scrs in a single phase half bridge converter? What difference does it make? (say in my attachment s2 and s3 are diodes instead of scrs?)
Wont we get the same operation with two scrs itself (only thing you have to fire them together with s1 and s4). I am confused. Please help.
 
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electricallov said:
why are we using two diodes instead of two scrs in a single phase half bridge converter? What difference does it make? (say in my attachment s2 and s3 are diodes instead of scrs?)
electricallov, your attachment is missing.
 
Im sorry. Now I've resubmitted.
 

Attachments

  • RLload.gif
    RLload.gif
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Hi electricallov. http://img96.imageshack.us/img96/5725/red5e5etimes5e5e45e5e25.gif

Offhand, I can't see a reason for not using 2 SCRs and 2 diodes here, at least for resistive loads. (Highly reactive loads can pose problems for SCRs, so I'd need to examine this closely to see whether that may be a consideration, especially when the L element is shown so prominently in the schematic here. :wink:)
 
Last edited by a moderator:
In my humble opinion,
if you use all four SCRs then you would end up with negative voltage output for a short duration before s2 and s4 are triggered.
 
GingerLee, this negative voltage concept solves everything. I did not notice the freewheeling path created when the two scrs are replaced by two diodes. This solves my question. Thanks
 

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