Year 2024

Week # 2 Quiz 2

Q1. A single-phase transformer is fed with a rated supply and operates at no load. If the core of the transformer is air-core, then the waveform of steady state magnetising current drawn from the supply would be a ___________.

Q2. A series DC generator delivers a load current of 50 A at 400 V and has armature and series field resistance of 0.05 Ω and 0.04 Ω respectively. Determine the induced emf in the armature if the brush contact drop is 1 V per brush.

Q3. Shunt generator running at 800 R.P.M. as the generated E.M.F. as 200 V. If the speed increases to 1000 R.P.M.(assuming other conditions to remain same). The generated E.M.F. will be

Q4. In a DC machine, the number of mechanical and electrical degrees will be same when the number of poles on the machine is

Q5. Which of the following is the most likely source of harmonics in a transformer ?

Q6. If the supply frequency for an induction motor is increased by 5%, then the synchronous speed will________

Q7. A 150 V DC motor of armature resistance 0.4 Ω has back emf of 142 V. The armature current is

Q8. The copper loss of a certain transformer at the half-full load is measured as 400 watts. The copper loss at full load will be

Q9. A three phase four pole 50 Hz induction motor has a rotor resistance of 0.02 \(\Omega\)/phase and stand-still reactance of 0.5 \(\Omega\)/phase. Calculate the speed at which the maximum torque is developed.

Q10. A synchronous motor, fed from infinite bus , is working at half load, if increased in it's field current causes a reduction in the armature current, then the motor is