On Load Tap Changer :- How it works? 

In this video you can understand through animation and in very simplified manner that how an OLTC i.e. On load tap changer works.
It is an important device, installed along with the winding assembly inside transformer tank and helps in changing tap position in transformer's High Voltage winding. Voltage regulation i.e. variation of terminals voltage with variation of load is the main concern which can be restricted to safe limit