1.  series

3.  cumulative compound

4.  differential compound

1.  A, B, C, A

3.  C, B, A, B

4.  B, A, B, C

1.  because the converter inherently does not provide for free-wheeling

3.  or else the free-wheeling action of the converter will cause shorting of the AC supply

4.  or else if a gate pulse to one of the SCRs is missed, it will subsequently cause a high load current in the other SCR

1.  

2.  

4.  

1.  True, because being majority carier devices, MOSFETs are voltage driven

2.  True, because MOSFETs have inherently anti-parallel diodes

3.  False, because it can be operated both as Current Source Inverter (CSI) or a VSI

1.  46 %

2.  55 %

3.  63 %

1.  S is always either zero or odd

2.  S is always either zero or even

3.  S = 1 only if the sum of A, B, C and D is even

1.  1  

2.  τ/2

3.  τ

1.  It makes a transition from - 5 V to + 5 V at t = 12.98 µs

2.  It makes a transition from - 5 V to + 5 V at t = 2.57 µs

3.  It makes a transition from + 5 V to - 5 V at t = 12.98 µs

2.  

3.  

4.