Off-load tap changers for transformers (DETC) are used to change the transmission ratio in order to adjust the transformer to grid conditions. Therefore tap changer for transformers have several pins to connect with the coil windings. ON-LOAD TAP CHANGER TYPE D General Manual On Load Tap Changer Type D 1. Specification Details Layout: Installed fully sunk in the transformer tank. (Can also be mounted in a separate tank). Diverter switch operates in its own oil space (diverter switch oil tank isolated from the transformer oil. Jul 01, 2018 · There are two main types of tap changer, on load, and off load, but this video focuses on the off load type only. Off load tap changers are used to vary the amount of secondary winding turns. By... Sep 10, 2016 · Off-Load Tap Changer is used for seasonal variation in voltage. A typical simplified diagram of Off-Load Tap Changer is shown in figure below. As shown in figure above, the winding is tapped from six locations corresponding to which six studs are provided. The six studs are arranged along the periphery of a circle.