A 3-phase Inductor Motor is driving a constant torque load at rated voltage and frequency. If both voltage and frequency are halved, following statements relate to the new condition if stator resistance, leakage reactance and core loss are ignored.
P. The difference between synchronous speed and actual speed remains same
Q. The air-gap flux remains same
R. The stator current remains same
S. The p.u. slip remains same
Among the above, correct statements are

A single phase induction motor with only the main winding excited would exhibit the following response at synchronous speed

Figure shows a $$\triangle$$ - Y connected 3-phase distribution transformer used to step down the voltage from 11000 V to 415 V line-to line. It has two switches S₁ and S₂. Under normal conditions S₁ is closed and S₂ is open. Under certain special conditions S₁ is open and S₂ is closed. In such a case the magnitude of the voltage across the LV terminals a and c is

A single phase transformer has a maximum efficiency of 90% at full load and unity power factor. Efficiency at half load at the same power factor is