gce 2022 intermediate level electrical machines 1

gce 2022 intermediate level electrical machines 1

gce 2022 intermediate level electrical machines 1

A single phase transformer has 200 turns on the
primary, 50 turns on the secondary and 120V
applied to the primary. What will be the secondary
voltage?
A 30V
B 24V
C 48V
D 83.3V

I (. To obtain magnetisation characteristics in a DC
generator, its field winding is to be
separately excited from an AC source
B separately excited from a DC
connected in parallel with the armature
D connected in series with the armature
2. The lifting power of an electromagnet depends on
A its weight
B its magnetic flux density
C its shape
D the material used

3. In a tic machine, (he yoke
A offers a path for current circulation
B offers mechanical protection to the machine
C produces working flux
D reduces core losses
12. The law which state that “ancmf induced in a
conducting coilis proportional to the rate of change
of flux linkage by the coir is:
*A Faraday’s first law
B Faraday’s first law
C Lenz’s law
D OhnVs law
4. Magnetic flux has as unit;
A Newton
B Ampere turn
C Tesla
D Weber
13. An ideal auto transformer is used to step down
voltage from V| to V2. An open-circuit occurs in the
• common portion of the winding. The voltage across
5. The role of a commutator in a dc generator is to the load then becomes
A increase the output voltage
B reduce sparking at the brushes
C provide smoother output
•D convcrtthc induced ac cmf to dc cmf
A V,
B • V2
C v,-v2
D Vt+V2
6. The role of brushes in dc generators is that
A theylead current into the armature coils
through the commutator
B they convert the ac generated voltage to dc
C they collect current from the commutator
D they smoothen the generated voltage
14. The most common coupling of a three phase
transformer for distribution is:
A Star-Delta
B Zig-Zag
C Delta-Delta
D Delta-Star
r
7. The quantity which is greater w’hcn a machine is
functioning as a motor is
A the terminal voltage
“B thegenerated emf
C the back emf
D the terminal voltage and generated emf
15. The connections suitable for 3-phase, 4 wire
distribution is:
• ‘A Y-A
B A-Y
C Y-Y
D A-A
8. One of the characteristics of a single phase moloris
that it
A is not self-starting
B is self-starting
C requires only one winding
D can rotate in one direction only
16. Two parts found in the rotor of induction motors
are:
A Rotor core and end covers
B Frame and rotor core
Rotor winding and terminal box
D Shaft and rotor core
C
9. The force on a current carrying conductor in a
magnetic Held is obtained using Fleming’s left hand
rule with the formula:
A F-BIV
B F=Blf
C F=BIR
D F=Blr
17. II the power transmitted to the rotor of a three phase
induction motor is 30KW and the motor has a slip
of 4%, what will be the copper losses in the rotor?
A 1.2KYV
B 7.5KW
C 30KAV
D I 20KW