Electrical Technology 3 2012
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GTHS KUMBO_Electrical Department_Third sequence exam……………………………Jan.2012 1 PART ONE : ELECTRICA L INSTALLA TION I. Generation : 1. Give two advant ages an d two disad vant ages of win d power ge neration over nuclear power generation. 2. Def ine renewable en erg y. Apart from wind ene rgy ; cite three othe r for ms of renewable energy. 3. Acco rding to y ou, why h as Cameroon chosen h ydro electr icity a s the main method of power generation? 4. Name in C ameroon: a) a n in terco nnecti on subs tation , b) A di strib ution stati on. 5. Give in MW, th e power of the follow ing g enera ting s tations: a) The hyd roe lec tric gen era ting st ati on a t Songl oul ou; b) The c oal fired therma l station a t Oy omaba ng; c) The therma l ge ner ati ng station at Bamenda . II. Electrical wiring system. 1. Give one a dvan tage and one disad vant age of each of the follow ing systems: a) Overhead wi ring sys tem; b) Und ergrou nd w iri ng sys tem. 2. Expl ain the reasons for th e us e of high volta ge (HV) for the tr ansmission of electrical energy. 3. A con duit carries the follow ing sy mbol: ICO5APE16. Give t he meanin g of ea ch indication. 4. Name two rooms of a domestic h ous e where it is forbidden to use woo den skirting trunking. REPUBLIC OF CAMEROON Peace – Work – Fatherland …………… GTHS KUMBO/ ELECT DPT THIRD SEQUENCE EXAM Class: F 3 7 Option: Electrotechnology Duration: 03H Coefficient: 2 Written paper ELECTRICAL AND ELECTRONIC TECHNOLOGY No document is allowed except the one given to the cand ida tes b the examiners.
Transcript of Electrical Technology 3 2012
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5. Give the size of conductor that can be used to supply the following loads:
a) incandescent lamp;
b) water heater
c) electric cooker
III. Safety
1. Give two methods used for the protection of persons against electrical shocks
resulting from direct contact.
2. In the neutral regime IT:
a) Which device is used for the protection of the network against overload?
b) Which device can be used to detect the first insulation fault?
c) Which procedure can be used to allocate the first insulation fault?
PART TWO: POWER ELECTRONICS
1. Name three application areas of power electronics.
2. Name three criteria of selection of a Zener diode.
3. Name three elements that facilitate the selection of a power diode.
4. Name two methods of triggering thyristors.
5. What is the difference between natural switching and controlled switching?
6. What are the advantages of controlled switching over natural switching?
7. Consider the single phase rectifier of the figure below.
D
R
E
UcvVd
0 t
v(t)
T/2T
i
a) Draw in synchronism with v, the waveforms of Uc(t), i(t) and Vd(t).
b) Give the expression of the maximum reverse voltage supported by the diode.
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PART THREE: ELCTRICAL MACHINE CONTROL
1. The name plate of a three phase squirrel cage motor contains the following
information: 220V/380V-50Hz; 8.0Cos ; %90 ; 22kW. The motor is used to drive
a wagon which carries logs of wood. The supply network is from AES-SONEL of
220/380V+N.
a) Define each parameter found on the nameplate.
b) Can this motor support star-delta starting? Justify you answer.
c) Name one possibility which can be used to limit the transient phenomenon
occurring during the passage from star to delta connection of the star-delta starting.
d) Give two methods that can be used for breaking this motor.
2. Give the role of the squirrel cage found on the stator of some three phase
alternator.
3. Which advantage does a deep slots or double cage induction motor have over a
normal induction motor?
4. Universal motor: a) explain the function of this motor. b) Give one domain of
application of this motor.
5. PLC: a) Give the meaning of PLC. B) Define the capacity of a PLC and precise its
unit. C) In which type of memory the instructions of a PLC are stored?
Subject Masters: Mr. AYUK Daniel, PLET.
Mr. NGOUNE Jean-Paul, PLET.
