NEW
Font size
WorksheetsElectrical machines 2 -Unit 1: Alternator principle
Total questions: 15
Worksheet time: 23mins
An alternator works on the principle of:
A. Electrostatic induction
B. Electromagnetic induction
C. Mutual induction
D. Self-induction
The frequency of induced emf in an alternator depends on:
A. Rotor diameter
B. Armature resistance
C. Speed of rotation and number of poles
D. Load current
Which part of an alternator produces the magnetic field?
A. Armature winding
B. Stator winding
C. Field winding
D. Slip rings
Salient pole alternators are generally used for:
A. High-speed applications
B. Low-speed applications
C. Portable generators
D. DC generation
Which type of alternator has a large diameter and short axial length?
A. Cylindrical rotor
B. Permanent magnet
C. Turbo alternator
D. Salient pole alternator
. Hunting in an alternator refers to:
A. Variation in terminal voltage
B. Oscillation of rotor about its synchronous position
C. Increase in armature current
D. Mechanical vibration due to imbalance
In short pitch winding, the coil span is:
A. Greater than pole pitch
B. Equal to pole pitch
C. Double the pole pitch
D. Less than pole pitch or 180° electrical
In a distributed winding, the conductors of a phase are:
A. Concentrated in one slot
B. Placed randomly
C. Distributed over several slots
D. Placed only in rotor slots
The synchronous speed of an alternator is given by:
A. N=60f/P
B. N=120f/P
C. N=P/120f
D. N=120Pf
The emf equation of an alternator is:
A. E=4.44fΦTph
B. E=2.22fΦTph
C. E=1.11fΦTph
D. E=6.66fΦTph
Which cooling method is used in large turbo alternators?
A. Natural air cooling
B. Forced air cooling
C. Hydrogen cooling
D. Oil cooling
The function of an exciter in an alternator is to:
A. Supply AC to stator
B. Supply DC to rotor field winding
C. Increase speed
D. Reduce losses
In a double-layer winding, each slot contains:
A. One conductor only
B. One coil side only
C. Two coil sides belonging to different coils
D. Two conductors of the same coil
Failure of cooling in an alternator may result in:
A. Improved efficiency
B. Reduced copper loss
C. Insulation breakdown
D. Higher power factor
Which of the following is used to reduce hunting in alternators?
A. Slip rings
B. Field winding
C. Damper winding
D. Armature winding
