(a) A chopper controlled electric train is powered from a 1500 VDE supply. The power semi- conductor switch element has a minimum effectice ON time of 40 Ms. during starting and slowspeed running, the output of the chopper has to go as low as 15 V. what is the highest chopper frequency possible to satisfy this reqirement ?
(b) The chopper in (a) has a minimum effective OFF time of 30 Ms. The chapper frequency is 2000Hz
(i) what is the maximum duty cycle and maximum output voltage possible?
(ii) if the full input voltage is to be made available to theload, show how this can be done