My doubt is when we intend to negative voltage from sinusoidal voltage as shown in the picture below, how does T3,T4 conducts when they are reverse biased(in positive half cycle). Graphically, Vout = (-V) makes sense but how would these thyristors even turn on with the gate pulses if they are reverse biased?
T3 and T4 still conducts in positive half cycle because of back emf generated by inductive load. Polarity of inductive load changes as soon as phase of input signal changes.
Back emf due to inductive load V = (do/di)(di/dt)= L(di/dt) = do/dt, variation of flux with variation of time, higher the L, more would be negative voltage...
Dear Bhupendra,
Follow the link for your answer.
https://www.google.com/url?sa=t&source=web&rct=j&url=https://nptel.ac.in/content/storage2/courses/108105066/PDF/L-10(DK)(PE)%2520((EE)NPTEL).pdf&ved=2ahUKEwjvprzVstjvAhUo_7sIHUVDAl0QFjAKegQIHBAC&usg=AOvVaw3OXKsMvfaKHr9afr1-9Pio
Viswanatha v. Bhupendra Desai Zia Hameed Thank you for your responses. Here it is alpha>90 and it is pretty clear that inductor will keep the thyristor pair on. I am currently learning a course called industrial drives by nptel which is archived. As shown the figure below we give pulses to T2 and a delayed one to T4 in positive cycle. Mathematically Vout= -Vin but how would T2 and T4 start conducting in positive cycle(similarly T1,T3 in negative cycle) since they are reverse biased. In the above case T1,T3 & T2,T4 are turned on in positive and negative cycles so no issues. (T1,2,3,4 are w.r.t the attached jpg below)
You have inductive load which return energy and polarises mentioned tyristors
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