Title Electrical Machine WB.pdf ✅

Address : Street 04, Narsingh Vihar, Katulbod, Bhilai 490022 (C.G.), Contact : 97131-13156 Live class room: https://play.google.com/store/apps/details?id=com.gateacademy1 Gate Academy Shop https://www.gateacademy.shop/ Online Test Series http://onlinetestseries.gateacademy.co.in Objective & Numerical Ans Type Questions : Q.1 A 3-phase, 2 pole, 400 V, 50 Hz, squirrel- cage induction motor is operating at a slip of 0.02. The speed of the rotor flux in mechanical rad/sec sensed by stationary observer, is closest to (A) 1500 (B) 1470 (C) 314.15 (D) 154 [GATE 2017, IIT Roorkee] Q.2 An 8-pole, 3-phase, 50 Hz induction motor is operating at a speed of 700 rpm. The frequency of the rotor current of the motor in Hz is _____. [GATE 2014, IIT Kharagpur] Q.3 The rotor of a three phase, 5 kW, 400 V, 50 Hz, slip ring induction motor is wound for 6 poles while its stator is wound for 4 poles. The approximate average no load steady state speed when this motor is connected to 400 V, 50 Hz supply is : (A) 1500 rpm (B) 500 rpm (C) 0 rpm (D) 1000 rpm [GATE 2002, IISc Bangalore] Q.4 The stator of a 4 pole, induction machine is supplied from , 50 Hz supply and a prime mover drives its rotor at a speed of 750 rpm. The slip rings of the machine are open circuited. The frequency of the voltage across any two slip rings is : (A) 50 Hz (B) 75 Hz (C) 100 Hz (D) 25 Hz [GATE 1994, IIT Kharagpur] Q.5 A three-phase 440 V, 6-pole, 50 Hz, squirrel cage induction motor is running at a slip of 5%. The speed of stator magnetic field with respect to rotor magnetic field and speed of rotor with respect to stator magnetic field are [GATE 2011, IIT Madras] (A) Zero, – 50 rpm (B) Zero, 950 rpm (C) 1000 rpm, – 50 rpm (D) 1000 rpm, 950 rpm Q.6 A 3-phase stator winding of a SCIM is fed by 3-phase ac supply at a frequency f. If the rotor speed is and synchronous speed is , then the absolute speed of resultant flux in space is (A) , irrespective of rotor speed (B) if the flux rotates in the same direction as the rotor (C) if the flux rotates in the same direction as the rotor (D) , irrespective of Q.7 A induction motor has 2 poles and is connected to 400 V, 50 Hz supply. When the slip is 4%, calculate the actual rotor speed and rotor frequency. (A) 2880 rpm, 2 Hz (B) 3120 rpm, 2 Hz (C) 2880 rpm, 48 Hz (D) 3120 rpm, 48 Hz Q.8 A , 6 pole, 50 Hz induction motor has a slip of 1% at no load and 3% at full load. Find : (i) No load speed and full load speed. (ii) Frequency of rotor current at standstill and at full load. 1 Principle of Operation 3-  3-  Nr Ns Ns Nr ( ) N N s  r ( ) N N s  r Nr Ns 3  3 