Taps are provided at the HV windings of the transformer because of the following reasons:
- The number of turns on high-voltage winding is large and hence a fine voltage variation can be obtained.
- The current on low voltage winding of the large transformer is high, therefore interruption of high current is a difficult taste.
- L.V. winding is placed nearer to the core and H.V. winding is placed outside. Therefore, providing taps on H.V. winding is comparatively easier than that of L.V. winding.
Transformer tappings are always done on the high-voltage side of the transformer. The high voltage side has a low current and vice versa for the low voltage side. When we use tappings due to the low current on the high voltage side, there will be fewer sparks and the turns are higher when compared to the LV side (low voltage, high current). Moreover, the HV side is outside the transformer so tappings are easily done on the HV side.