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A single-phase half controlled converter shown in the figure given below is feeding power to highly inductive load. The converter is operating at a firing angle of 60° . If firing pulses are suddenly removed, then steady state voltage (v0) waveform of the converter will become
Correct Option: B
Single phase half controlled converter.
For highly inductive load, load current is almost constant.
During, 0 < ωt < α
freewheeling will be done by T2D1, V0 = 0
For, α < ωt < π
T1D1 conducts V0 = Vs
For π < ωt < π + α
Freewheeling will be done by T1D2, V0 = 0
For π + α < ωt < 2π
T2D2 conduct, V0 = – Vs
T1 is again triggered at 2π + α
Hence, during 2π + α < ωt < 3π, T1D1 conducts.
Now, if firing pulses are removed after T1 is triggered at 2π + α.
At ωt = 3π + α, no firing pulse will be available to trigger T2. So, load current will flow through T1D2 as load current is continuous. So during 3π + α + ωt < 4π, TD2 will continue to conduct and V0 = 0
At, ωt = 4π, Diode D1 will become forward-biased and therefore D2 will become reverse-biased.
Hence, D1 will conduct and as T1 is already in conduction, load current will flow through T1D1 and then V0 = Vs
