For a specified input voltage and frequency, if the equivalent radius of the core of a transformer is reduced by half, the factor by which the number of turns in the primary should change to maintain the same no load current is

A star connected 400 V, 50 Hz, 4 pole synchronous machine gave the following open circuit and short circuit test results:
Open circuit test: V_OC = 400 V (rms, line–to–line) at field current, I_f = 2.3 A
Short circuit test: I_SC = 10 A(rms, phase) at field current, I_f =1.5 A
The value of per phase synchronous impedance in Ω at rated voltage is __________.

A 3 phase, 50 Hz, 6 pole induction motor has a rotor resistance of 0.1 Ω and reactance of 0.92 Ω. Neglect the voltage drop in stator and assume that the rotor resistance is constant. Given that the full load slip is 3%, the ratio of maximum torque to full load torque is

The following four vector fields are given in cartesian coordinate system. The vector field which does not satisfy the property of magnetic flux density is