Question

Q1A 4-poles, wave wound, 600 conductors DC long shunt generator has the armature, series and shunt resistances are 0.15 ohm, 0.18 ohm and 200 ohm respectively. It runs at 1500 rpm. Calculate the following if it is required supply to the load resistance of 20ohm with flux per pole as 8.33 mWb. Take the Iron and Frictional losses as 550 W.(i)Induced Emf(ii)Terminal Voltage(iii)Output Power(iv)Input Power(v)Efficiency

Q2Write short notes on following characteristics of dc generator(i) Open Circuit Characteristics (OCC)(ii) Load Characteristics

Q3A dc short shunt generator supply 500V to a 20 kW load. Its armature, series and shunt resistance are 0.8 , 0.6 and 700 respectively. Calculate the armature current, induced emf, input power, torque supplied by the prime mover and efficiency if its speed and mechanical losses are 1500 rpm and 910W respectively.

Q4A 500V, 4 poles, wave-wound DC Series Motor has 900 conductors on its armature. It has armature and series field resistance of 0.6, and 0.8respectively. The motor takes a current of 40A. Estimate the speed and gross Torque developed if it has a flux per pole of 20mWb.

Q5A dc shunt motor takes a no load current of 5 A at 300V. Its armature and shunt resistances are 0.45 ohm and 0.68 ohm respectively. Calculate the Constant Loss (Iron and Frictional Loss) of the machine.

Q6A dc series motor operates at 1000 rpm with a line current of 82A from 250V mains. its armature circuit resistance is 0.2and its field resistance is 0.6. Find the speed at which the motor runs at a line current of 65A, assuming that the flux at this current is 33% of the flux at 82A.

Q7A 3 phase, 50Hz, 4 poles induction motor runs at 1440 rpm. Calculate the following i.Synchronous speedii.Slipiii.Slip speediv.Rotor frequency while runningv.Rotor cu loss if mechanical power developed is 16 kW.

Q8A 40 kW (Rated Output), 415V, 50Hz, 3 phase, star connected induction motor has a synchronous speed of 1800 rpm. The full load slip is 4% and full load power factor is 0.9 lagging. Stator Cu losses are 2500 W. Iron losses are 2000W. Rotational losses are 1400 W. Calculate i.Shaft or Net Torque developedii.Mechanical power developediii.Power inputiv.Efficiencyv.Supply current

Q9The following are the equivalent circuit parameters of a 3phase, star connected 415V, 50Hz, 4 poles Induction Motor:R1= 0.5, R'2= 0.4/s , X1= 0.9, X'2= 0.8, Xm= 50,(neglect Ro)Calculate the input impedance, motor current, power input, power supplied to the rotor, power developed and efficiency if its rotational losses are 1200W. It runs at 1410 rpm.

Q10A 415-V, 29.84 kW, 50 Hz, delta-connected 3-phase induction motor gave the following test data:No load test:415V, 15A, 2000 WLocked rotor test:125V, 40A, 4000 WConstruct the circle diagram and determine the line current and power factor for the rated output. Assume stator and rotor Cu losses equal at standstill.Q11With a aid of neat circuit diagram, explain the working principle of Automatic star-delta starter of three phase induction motor

Answer 1