Disc switch

When the transformer is de-energized and in a non-excitation state, the connection of the high-voltage winding taps is changed by rotating the disc to adjust 

the transformer transformation ratio and achieve fine-tuning of the output voltage.

Rotary switching: Turning the handle → the rotating shaft drives the moving contact to rotate → connecting different static contacts (winding taps) → changing 

the effective turns of the high-voltage winding → adjusting the transformation ratio and output voltage.