PYQs Based test 10: Electrical Machines

A three-phase, $50Hz$ salient-pole synchronous motor has a per-phase direct-axis reactance $\left(X_d\right)$ of $0.8pu$ and a per-phase quadrature-axis reactance $\left(X_q\right)$ of $0.6pu$. Resistance of the machine is negligible. It is drawing full-load current at 0.8 pf (leading). When the terminal voltage is $1pu$, per-phase induced voltage, in $pu$, is _________.

A 15 kW, 230 V dc shunt motor has armature circuit resistance of 0.4 Ω and field circuit resistance of 230 Ω. At no load and rated voltage, the motor runs at 1400 rpm and the line current drawn by the motor is 5.A. At full load, the motor draws a line current of 70 A. Neglect armature reaction. The full load speed of the motor in rpm is______

The figure shows the per-phase equivalent circuit of a two-pole three-phase induction motor operating at 50 Hz. The “air-gap” voltage, $V_g$ across the magnetizing inductance, is 210 V rms, and the slip, is 0.05. The torque (in Nm) produced by the motor is _______.

Find the transformer ratios a and b that the impedance Zᵢₙ is resistive and equal to 2.5 Ω when the network is excited with a sine wave voltage of angular frequency of 5000 rad/s

A three-phase, 11 kV, 50 Hz, 2 pole, star connected, cylindrical rotor synchronous motor is connected to an 11 kV, 50 Hz source. Its synchronous reactance is 50 Ω per phase, and its stator resistance is negligible. The motor has a constant field excitation. At a particular load torque, its stator current is 100 A at the unity power factor. If the load torque is increased so that the stator current is 120 A, then the load angle (in degrees) at this load is ________.