GATE 2019: Electrical Machines Rapid Quiz 2 (App update required to attempt this test)

A 440V, 50 Hz squirrel cage induction motor has a ratio of standstill reactance to resistance of rotor per phase of 3 to 1 and a maximum torque which is 4 times the normal full-load torque. What will be the full-load slip (in percentage )?

A transformer with tororidal core of permeability μ is shown in the figure. Assuming uniform flux density across the circular core cross-section of radius r<<R, and neglecting any leakage flux, the best estimate for the mean radius R is

A star-connected, 12.5 kW, 208 V (line), 3-phase, 60 Hz squirrel cage induction motor has following equivalent circuit parameters per phase referred to the stator: Neglect shunt branch in the equivalent circuit. The starting current (in Ampere) for this motor when connected to an 80 V (line), 20 Hz, 3-phase AC source is __________.

A three-phase, 50Hz, star-connected cylindrical-rotor synchronous machine is running as a motor. The machine is operated from a 6.6 kV grid and draws current at unity power factor (UPF). The synchronous reactance of the motor is 30 per phase. The load angle is .The power delivered to the motor in kW is _______.

Two parallel connected, three-phase, 50Hz, 11kV, star-connected synchronous machines A and B, are operating as synchronous condensers. They together supply 50 MVAR to a 11 kV grid. Current supplied by both the machines are equal. Synchronous reactance’s of machine A and machine B are 1Ω  and 3Ω respectively. Assuming the magnetic circuit to be linear, the ratio of excitation current of machine A to that of machine B is ________.