1. The emf equation of DC generator is E
2. A 220 V separately excited dc motor takes 20 A and the armature resistance is 1.0 Ω. If the armature constant KaΦ = 1.5 rad/sec, the speed of the motor is
3. In which mode machine is operating, given that conductor current is in the same direction as conductor emf?
- Can’t be determined using directions
- In both modes for different cycles
4. A 4-pole Dc wound machine is lap wound with 400 conductors. The pole shore is 20 cm long and the average flux density over the one-pole pitch is 0.4 T, the armature diameter is 30 cm. What is the value of flux/pole?
- 0.188 Wb
- 18.88 Wb
- 0.0188 Wb
- 1.888 Wb
5. In a DC machine, let ϕ be the flux per pole, ωm be the armature speed in rad/s, Nc be the number of coil turns in the armature and P be the number of poles. What will be the average coil EMF in that machine?
- Ea = φωmNc/P
- Ea = φωmNcP/60
- Ea = ϕωmNcP
- Ea = φωmNcP/π
6. Nature of the flux density wave in the air gap is __________ (for armature current equal to 0).
- Flat-topped with quarter-wave symmetry
- Point topped with quarter-wave symmetry
- Flat-topped with half-wave symmetry
- Point topped with half-wave symmetry
7. A 4-pole Dc wound machine is lap wound with 400 conductors. The pole shore is 20 cm long and the average flux density over the one-pole pitch is 0.4 T, the armature diameter is 30 cm. What is the value of induced emf?
- 188 V
- 276 V
- 94 V
- 188 mV
8. A four-pole, lap-would DC machine has 462 conductors in the armature. The average flux per pole is 0.02 Wb. Determine the induced armature voltage when the armature rotates at 1000 rpm.
9. In a DC machine, the average energy stored in the magnetic field remains _______ of the armature rotation.
- Any of the above
10. Coil torque for 20 kA armature current (T1) and 40 kA armature current (T2), will have a ratio T1/T2 = ____ (assuming all other parameters same for both machines).