Two semiconverters are connected in series to form a single phase series converter. The input v = Vm sin t and a1 = a2 are the firing angles of the two converters. If a1 = a2 = 0, the dc output voltage is

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• B. <img src="/_files/images/electronics-and-communication-engineering/power-electronics/267-52-1.png">
• C. <img src="/_files/images/electronics-and-communication-engineering/power-electronics/278-273-1.png">
• D. <img src="/_files/images/electronics-and-communication-engineering/power-electronics/278-273-2.png">