Several online articles mention the so-called "Single phase SCR Inverter". Sample schematic is attached below.

Source: Single Phase Full Bridge Inverter Explained | Electrical Concepts

In reality, this, of course, will not work, since SCR2 when activated after SCR1, will short the power supply. Obviously, the schematic is missing the circuit that would turn SCRs off.

I searched through the net and found no real implementation of this idea. Can anyone please elaborate on this and share a working schematics of an SCR inverter? Also, what is the advantage of using SCRs over MOSFETs here?

  • \$\begingroup\$ Please link to the article that the pictures came from. \$\endgroup\$
    – Andy aka
    Feb 10, 2022 at 13:28
  • \$\begingroup\$ This is a classical H-Bridge without the circuit controling it. 4 Thyristors (SCR) that can basically "cross out" the input DC voltage thus creating an AC output voltage. The controling circuitry has to make sure that SCR1 and SCR2 (or SCR3 and SCR4) are never switched on at the same time. GTO-Thyristors can be switched off with a negative pulse on the gate. \$\endgroup\$
    – kruemi
    Feb 10, 2022 at 13:35
  • \$\begingroup\$ kruemi, thanks, but this is sort of given. I am looking for a schematics that would work with non-GTO thyristors. Otherwise, the circuit does not make sense. \$\endgroup\$ Feb 10, 2022 at 14:22
  • \$\begingroup\$ Controlling circuit is not shown here, it's obvious. And we are dealing with regular "turn on only" thyristors here. I don't understand the advantages of using SCRs here given all the circuitry needed to turn them off. That is the question, actually. Also, I failed to find a sample of such circuitry online. Numerous websites copy-paste this schematic w/o actually giving detail on how SCRs are supposed to turn off. \$\endgroup\$ Feb 10, 2022 at 14:28
  • 1
    \$\begingroup\$ @JimmyFalcon you said this in your question: Several online articles mention the so-called "Single phase SCR Invertor" and I asked where the pictures came from. Anyone making a decent attempt at an answer has to start with what information you posted. \$\endgroup\$
    – Andy aka
    Feb 10, 2022 at 17:41

2 Answers 2


Also, what is the advantage of using SCRs over MOSFETs here?

The advantage of SCR inverters is that power MOSFETs and other high power switching devices were not available when SCR inverters were invented. SCR inverter technology began to be replaced about 50 years ago. There is not much to be found about it today.

The commutation circuit that was "simplified" out of the schematic more than doubles the complexity of the circuit. Force-commutation circuits typically used another pair of SCRs and an LC circuit to divert the current from the main path for about 25 to 50 microseconds. Some circuits had a commutation circuit for each pair of load-carrying SCRs. Others had just one pair of commutation SCRs and commutated all of the load carrying SCRs whenever one needed to be commutated. Some inverters used a large inductor in the DC supply to give the supply a short-term current-source characteristic. Steering the current rather than switching the voltage made commutation easier. There were also load-commutated inverters that used load characteristics to commutate the SCRs.

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    \$\begingroup\$ So the LC was suppose to ring and that would shut off the thyristors diverting the current? \$\endgroup\$
    – DKNguyen
    Feb 10, 2022 at 15:51
  • \$\begingroup\$ Just to add that SCRs are ok for driving three phases motors. And I know also DHR systems (super-fast circuit breakers) that can break 10 kA in 5 ms without arcing. \$\endgroup\$
    – Antonio51
    Feb 10, 2022 at 17:27
  • \$\begingroup\$ In french ... What is a DHR patentimages.storage.googleapis.com/bd/e4/73/b33e94e0ea2606/… \$\endgroup\$
    – Antonio51
    Feb 10, 2022 at 18:09
  • \$\begingroup\$ @DKHguyen, I don't remember exactly how the various commutating schemes worked. The point is that there were several schemes used in various products that were on the market in the mid 1960's through the 1970's. They made the power circuit considerably more complicated that the one in the question. The GE SCR Manual of 1972 lists six distinct classes of forced commutation methods some of them used LC pulse shaping schemes. \$\endgroup\$
    – user80875
    Feb 11, 2022 at 1:49

The schematic should be ...

From this

enter image description here


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