A synchronous phase modifier as compared to the synchronous motor has same rating has

A. larger shaft diameter and higher speed
B. Smaller shaft diameter and higher speed
C. larger shaft diameter and smaller speed
D. smaller shaft diameter and smaller speed

Answer: B. Smaller shaft diameter and higher speed

Explanation:

synchronous compensator:

• If it is under the excited condition, it draws the lagging current and, therefore, supplies capacitive or absorbs inductive volt-ampere reactive. 
• Thus, a current drawn by a synchronous capacitor or condenser can be varied from lagging to leading smoothly by varying its excitation.
• Synchronous Condensor is also known as Synchronous Compensator or  Synchronous Phase Modifier. 
• A synchronous condenser or a synchronous compensator is a synchronous motor running without a mechanical load.
• It can generate or absorb reactive volt-ampere (VAr) by varying the excitation of its field winding. 
• It can be made to take a leading current with over-excitation of its field winding.
• In such a case it delivers inductive or absorbs capacitive volt-ampere reactive. 
• If it is under the excited condition, it draws the lagging current and, therefore, supplies capacitive or absorbs inductive volt-ampere reactive. 
• Thus, a current drawn by a synchronous capacitor or condenser can be varied from lagging to leading smoothly by varying its excitation.
• Synchronous phase modifiers are installed at load end.
• Synchronous phase modifiers do not carry Load.
• Synchronous phase modifiers are nothing but synchronous motors.