Test: Electrical Machines- 2 - Electrical Engineering (EE) MCQ

A d.c. series motor is accidently connected to single-phase a.c. supply. The torque produced will be

The ‘synchronous-impedance method’ of finding the voltage regulation by a cylindrical rotor alternator is generally considered as

Generally the no-load losses of an electrical machine is represented in its equivalent circuit by a

The power factor of a synchronous motor

A 6-pole, 3-phase alternator running at 1000 rpm supplies to a 8-pole, 3-phase induction motor which has a rotor current of frequency 2 Hz. The speed at which the motor operates is

For maximum current during ‘Slip Test’ on a synchronous machine, the armature mmf aligns along

A 3-phase 50 MVA 10kV generator has a reactance of 0.2 ohm per phase. Hence the per-unit value of the reactance on a base of 100 MVA 25 kV will be

The results of a ‘Slip-Test’ for determining direct-axis (X_d) and quadrature-axis (X_q) reactances of a star-connected, salient-pole alternator are given below:

Phase values: V_max = 108V; V_min = 96V, I_max = 12A, I_min = 10A. Hence the two reactances will be 

A two-winding transformer is used as an auto-transformer. The kVA rating of the auto-transformer compared to the twowinding transformer will be

A 20 kVA, 2000/200V, 1-phase transformer has name-plate leakage impedance of 8%. Voltage required to be applied on the high-voltage side to circulate full-load current with the low-voltage winding short-circuited will be

The full-load copper-loss and iron loss of a transformer are 6400W and 5000W respectively. The copper-loss and ironloss at half load will be, respectively

In a 100 kVA, 1100/220V, 50 Hz single-phase transformer with 2000 turns on the high-voltage side, the open-circuit test result gives 200V, 91 A, 5kW on low-voltage side. The coreloss component of current is approximately

For a given torque, reducing the diverter-resistance of a d.c. series motor

Possible three-to-three phase transformer connection for parallel operation is

A 4 kVA, 400/200V single-phase transformer has resistance of 0.02 p.u. and reactance of 0.06 p.u. Its actual resistance and reactance referred to high voltage side are respectively

Two 10 kV/440V, 1-phase transformers of ratings 600 kVA and 350 kVA are connected in parallel to share a load of 800 kVA. The reactances of the transformers, referred to the secondary side are 0.0198Ω and 0.0304Ω respectively (resistances negligible). The load shared by the two transformers will be respectively

The current drawn by a 120V d.c. motor with back e.m.f. of 110V and armature resistance of 0.4 ohm is