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PART ONE TECHNOLOGY /10marks
I- QUESTIONS /5marks
1. Give two main reasons for dividing an installation into many
circuits (0.5
marks)
2. a) Name three methods of starting a fluorescent lamp. b) Why
is the tungstenused for the manufacturing of the filament of
filament lamp? (3x0.5+1 marks)
3. A fuse possesses some characteristics; name and state the
meaning of these
characteristics (2 marks).
II- EXERCISE: Lighting /5 marks
A school classroom 7mx10mx4m height is to be illuminated to
135lm/m2 on
the working plane. If the coefficient of utilization is 0.45 and
the sources give 13
lumens per watt, work out the total wattage required, assuming a
depreciation factor
of 0.8. Sketch roughly the plan of the room, showing suitable
positions for fittings,
giving reasons for the positions chosen.
PART TWO: DRAWING /10 marks
Theme 1: Electrical installation of a villa /4 marks
The layout diagram given in annex (page 3/3) represents the
electrical installation of
Mr. BELL BELL at ESEKA.
WORK TO BE DONE:
Take 5 apparatus per circuit in maximum for each lighting or
socket circuits. With the
help of the architectural diagram given in annex (page 3/3):
1. Give the number of lighting circuits and the number of socket
circuits.
(1 mark).
2. Determine the total number of circuits of the villa.
(mark)
3. Establish a single wire diagram of circuits of the
installation; indicate the
section of each conductor in the diagram. (2marks).
REPUBLIC OF CAMEROONPeace Work Fatherland
GTHS KUMBO/ ELECT DPT
MOCK EXAMINATIONS
Class: F36
Option: Electrotechnology
Duration: 03H
Coefficient: 3
Written paper
DRAWING AND TECHNOLOGY
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GTHS KUMBO_Electrical Department_Mock exam......March.2012 2
Theme 2: Control of the motor of a saw.
I- Description:
In a wood factory, timbers are transformed into plank through
the following process:
The timber is placed on a movable bench. The bench driven by a
three phase
asynchronous motor, takes the timber to the right direction for
the sawing process,
and back left at the initial position.
II- Operation:
When the isolator is switched on:
An impulse on the push button S1 provokes the motion of the
bench with the
timber towards the saw. The timber, as it is approaching the
saw, cuts the light
of the sensor S2, to start the saw. The sawing operation is
executed and at the
end, the piece of plank shall operate during its fall a limit
switch S3 to reverse
the direction of motion of the bench with the timber and stop
the saw. When
the timber reaches the initial position, it operates a limit
switch S4 which stops
the motion of the bench. The position of the timber is then
adjusted
mechanically for the next cycle to start.
The execution of a cycle can be stopped at any moment through an
action on
S0. The execution of a cycle is signalled by a pilot lamp H1,
while a fault on
the motor M1 is signalled by H2. The electrical installation of
the saw motor is
not considered.
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NB: The motor is protected by a thermal relay F2. the control
circuit is protected by a
fuse F1. Supply network: 380V+N
WORK REQUIRED:
1. Establish the power circuit of the motor. (2marks)
2. Establish the control circuit of the installation.
(4marks)
Good luck for your Probatoire exam
Tel electrical Department.
