Bro, I dont catch ur question correctly. As far as I understand.......
Tap changers are generally used on low current side (HV side) so that the current to be handled is less. In case of an on-load tap changer, before the existing tap is opened, the next tap to be closed is closed and then the existing tap is opened. This is to ensure continuity of supply. but by this, the no of turns between these two taps will be short citcuited for a brief period. There are many methods to avoid this short circuit ( refer any book on on-load tap changers). Tap change produces harmonics. OFF -load tap changers have no problems except that the load is to be shut before tap is changed.
Bro, I dont catch ur question correctly. As far as I understand.......
Tap changers are generally used on low current side (HV side) so that the current to be handled is less. In case of an on-load tap changer, before the existing tap is opened, the next tap to be closed is closed and then the existing tap is opened. This is to ensure continuity of supply. but by this, the no of turns between these two taps will be short citcuited for a brief period. There are many methods to avoid this short circuit ( refer any book on on-load tap changers). Tap change produces harmonics. OFF -load tap changers have no problems except that the load is to be shut before tap is changed.
I think this practice varies between countries. I understand that HV tap changers are usual in Europe and LV tap changers are common in America. The LV tap changers break larger currents so contact maintenance and oil condition can be a maintenance issue.