A $$PWM$$ switching scheme is used with a three phase inverter to

A three phase diode bridge is used to provide rectified output from a $$400V,$$ $$50$$ $$Hz,$$ $$3$$- phase supply to a $$R$$ $$-$$ $$L$$ load with $$10\,\,\Omega $$ resistance and $$300$$ $$mH$$ inductance.
Determine the
(a)$$DC$$ level of the output voltage
(b) $$RMS$$ value of the diode current
(c) $$RMS$$ value of the source current, and
(d) Apparent power drawn from the mains

An overhead line having a surge impedance of $$400$$$$\Omega $$ is connected in series with an underground cable having a surge impedance of $$100$$$$\Omega $$. If a surge of $$50$$ $$kV$$ travels from the line end towards the cable junctions, the value of the transmitted voltage wave at the junction is

Corona losses are minimized when