The Voltage Source Inverter $(VSI)$ shown in the figure below is switched to provide a $50 Hz$, square-wave ac output voltage $(vo)$ cross an $R-L$ load. Reference polarity of $vo$ and reference direction of the output current $i_0$ are indicated in the figure. It is given that $R = 3 \Omega$, $L = 9.55 mH$

Appropriate transition i.e., Zero Voltage Switching $(ZVS)$/Zero Current Switching $(ZCS)$ of the $IGBTs$ during turn-on/turn-off is

1. ZVS during turn-off
2. ZVS during turn-on
3. ZCS during turn-off
4. ZCS during turn-on

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