What are common types of tap changers?

• A. Terminal board and rotary switch.
• B. Electronic and digital.
• C. Hydraulic and pneumatic.
• D. Fixed and movable.

Answer: (A)

Tap changers adjust a transformer's output voltage by selecting different turns on the winding. The common mechanical ways this selection is made are: a terminal board approach, where taps are brought out to a terminal board and connected via contacts; and a rotary switch approach, where a rotating contact connects to the chosen tap. These represent the primary ways the connections are made to pick different voltages.

The other options don’t describe the typical switching mechanisms for tap changers. Electronic or digital usually refer to control logic rather than the actual switching method. Hydraulic or pneumatic describe actuation methods, not the standard tap-selection method. Fixed and movable isn’t a standard classification for how taps are selected in transformer windings.