If the vector $$\left[ {\matrix{ 1 \cr 2 \cr { - 1} \cr } } \right]$$ is an eigen vector of $$A = \left[ {\matrix{ { - 2} & 2 & { - 3} \cr 2 & 1 & { - 6} \cr { - 1} & { - 2} & 0 \cr } } \right]$$ then one of the eigen value of $$A$$ is

If $$A = \left[ {\matrix{ 5 & 0 & 2 \cr 0 & 3 & 0 \cr 2 & 0 & 1 \cr } } \right]$$ then $${A^{ - 1}} = $$

A $$3$$-phsae, fully controlled, converter is feeding power into a $$d.c.$$ load at a constant current of $$150A.$$ The $$r.m.s$$ current through each thyristor of the converter is

When the firing angle $$\alpha $$ of a single phase, fully controlled rectifier feeding constant $$d.c.$$ current into a load is $${30^ \circ }$$ , the displacement power factor of the rectifier is