The supply for the charger is from MCC. The supply is tapped for power supply to control card, PF correction capacitor. LC filter is used for suppressing surge voltage. The main supply is stepped down and given to the half control rectifier module. The SCR conducts only when gate gets positive pulse. This pulse is given by pulse transformer, which gets pulses from firing card. Firing card gives pulse to the respective RYB SCR only when their phases are positive maximum. The freewheel diode is incorporated to protect the SCR and diodes from back emf when supply to coils is cut off due to collapsing magnetic field.
The filter is provided to smoothen the ripple output and the bleeder is used for voltage regulation. It gives improved voltage regulation and acts as a minimum load. Also it keeps the SCR in conducting state by drawing the minimum current which is higher than the SCR holding current. Thus there is always output voltage irrespective of load
DC CT is used for limiting output current. It works on principle of magnetic amplifier. There is also provision for smooth rising of output voltage.
