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EIN03
Candidate Code No.
For Board Use Only
Result
Date
Int
Result
Date
Int
ELECTRICAL INSTALLER THEORYEXAMINATION
19 November 2011
QUESTION AND ANSWER BOOKLET
Time Allowed: Three hours
INSTRUCTIONS READ CAREFULLY
You have 10 minutes to read this paper but do not start writing until you are told todo so by the supervisor.
Write your Candidate Code Number in the box provided above. Your name must NOT
appear anywhere on this paper.
Answer all questions.
The pass mark for this examination is 60 marks.
Use a pen for written answers. Do not use a pencil or a red pen.
Drawing instruments and pencils may be used when diagrams are required. Marksare allocated on the basis of correctness.
Do not use correcting fluid or correcting tape.
For calculation questions all workings, including formulae, must be shown to gain fullmarks.
Non-programmable calculators may be used.
Warning You could get 0 marks for any question, or part of a question, if you showanything hazardous or dangerous in your answer.
Candidates are not permitted to use any Act, Regulation, Standard, Code ofPractice, Handbook or other reference text in this examination.
PLEASE HAND THIS PAPER TO THE SUPERVISOR BEFORE LEAVING THE ROOM.
(turn over)
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EIN03- QUESTIONS 19 NOVEMBER 2011 2
Question 1
(a) (i) An earth continuity (protective earthing) test has been carriedout on a repaired 230V, Class I, plug-in electrical appliance.
State an acceptable test result value for the earth continuity testthat will permit the electrical appliance to be returned to service.
(1 mark)
________________________________________________________
(ii) An insulation resistance test has been carried out on a repaired230V, Class II, plug-in electrical appliance.
State an acceptable test result value for the insulation resistancetest that will permit the electrical appliance to be returned to service.
(1 mark)
________________________________________________________
(b) (i) State the TWO functions that operate in a MCB.(1 mark)
(1) ____________________________________________________
(2) ____________________________________________________
(ii) Define the term AC 80 as found on an HRC fuse cartridge.(1 mark)
________________________________________________________
________________________________________________________
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EIN03- QUESTIONS 19 NOVEMBER 2011 3
Question 1 continued
(c) (i) State the TWO main functions of a choke (ballast) in a fluorescentlight fitting?
(1 mark)
(1) ____________________________________________________
____________________________________________________
(2) ____________________________________________________
____________________________________________________
(ii) State TWO factors that reduce the life of an incandescent lamp(1 mark)
(1) ____________________________________________________
(2) ____________________________________________________
(d) In the New Zealand MEN system the neutral is earthed at the star pointof a transformer; on the distribution system; and at the main switchboardof an installation.
State the TWO main reasons why the neutral is earthed in the NewZealand MEN system
(2 marks)
(1) ________________________________________________________
________________________________________________________
________________________________________________________
(2) ________________________________________________________
________________________________________________________
________________________________________________________
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EIN03- QUESTIONS 19 NOVEMBER 2011 4
Question 1 continued
(e) A three-phase, fixed-wired electrical appliance that has been operatingnormally is to be removed for maintenance.
An isolating switch has been turned off. A voltage test was carried out atthe appliance terminals to test for isolation.
The testing showed terminals to be live. State TWO possible causes forthis situation.
(2 marks)
(1) ________________________________________________________
________________________________________________________
(2) ________________________________________________________
________________________________________________________
(f) The tests on a star-connected squirrel cage motor show the followingreadings:
L1 L2 20L1 L3 open circuitL2 L3 open circuit
State the most likely fault indicated by these readings.(2 marks)
____________________________________________________________
____________________________________________________________
(g) One reason why the metal frame of a Class I electrical appliance is earthedis to ensure the operation of a protective device under fault conditions.
State ONE other reason why the metal frame of a Class I electricalappliance is earthed.
(2 marks)
____________________________________________________________
____________________________________________________________
____________________________________________________________
____________________________________________________________
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EIN03- QUESTIONS 19 NOVEMBER 2011 5
Question 1 continued
(h) State the reason why a run capacitor is fitted to a single-phase split-phase induction motor.
(2 marks)
____________________________________________________________
____________________________________________________________
____________________________________________________________
____________________________________________________________
(i) (i) Define the term pullout torque as it applies to an a.c. inductionmotor?
(1 mark)
________________________________________________________
________________________________________________________
(ii) State the synchronous speed of a three-phase 400V, 50Hz, four-poleinduction motor?
(1 mark)
________________________________________________________
________________________________________________________
(j) State TWO components that can be used as part of a circuit to filter arectifier output.
(2 marks)
(1) ________________________________________________________
(2) ________________________________________________________
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EIN03- QUESTIONS 19 NOVEMBER 2011 6
Question 2
Danger tags and out-of-service tags are used extensively in workplaces.
(a) Two registered electrical installers are carrying out electrical repairs on thesame refrigeration plant.
(i) State the main reason why danger tags are used.(2 marks)
________________________________________________________
________________________________________________________
________________________________________________________
________________________________________________________
________________________________________________________
________________________________________________________
(ii) State THREE actions to be taken when attaching danger tags to anisolating switch of the refrigeration plant.
(3 marks)
(1) ____________________________________________________
____________________________________________________
(2) ____________________________________________________
____________________________________________________
(3) ____________________________________________________
____________________________________________________
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EIN03- QUESTIONS 19 NOVEMBER 2011 7
Question 2 continued
(iii) State the TWO circumstances where the danger tags can beremoved.
(2 marks)
(1) ____________________________________________________
____________________________________________________
____________________________________________________
(2) ____________________________________________________
____________________________________________________
____________________________________________________
(b) Describe the circumstances where an out-of-service tag is used(2 marks)
____________________________________________________________
____________________________________________________________
____________________________________________________________
____________________________________________________________
____________________________________________________________
____________________________________________________________
(c) You are doing a polarity test at the supply side of a three-phase main
switch to see if the switchboard is isolated.
Between which terminals would you test to clearly establish that isolation(or otherwise) has taken place.
(1 mark)
____________________________________________________________
____________________________________________________________
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EIN03- QUESTIONS 19 NOVEMBER 2011 8
Question 3
The method of installing cables in electrical installations depends on theenvironment in which the wires and cables are to be installed.
(a) TPS sheathed PVC cables are installed in an electrical installation, bothindoors and outdoors.
(i) State TWO reasons why some TPS sheathed cables would be installedin PVC conduit.
(2 marks)
(1) ____________________________________________________
____________________________________________________
(2) ____________________________________________________
____________________________________________________
(ii) State TWO design requirements to be considered when PVC conduit isused outdoors.
(1 mark)
(1) ____________________________________________________
(2) ____________________________________________________
(iii) State the requirement for installing extra-low voltage cables in thesame conduit and low voltage PVC cables.
(1 mark)
________________________________________________________
________________________________________________________
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EIN03- QUESTIONS 19 NOVEMBER 2011 9
Question 3 continued
(b) Within the installation cables are installed in open cable ladders and opencable trays.
(i) Some cables carry large currents.
State the reason why is it necessary to securely fasten cables carryinghigh currents when installed in horizontal cable trays.
(2 marks)
________________________________________________________
________________________________________________________
________________________________________________________
(ii) What provision is made when telecommunication cables are installedin the same tray as low voltage cables?
(1 mark)
________________________________________________________
________________________________________________________
________________________________________________________
(iii) What provision is made where an open cable tray passes through thefire-rated wall of a switch room?
(1 mark)
________________________________________________________
________________________________________________________
________________________________________________________
(c) State the main effect on TPS sheathed cables that are installed throughwalls containing thermal insulation.
(2 marks)
____________________________________________________________
____________________________________________________________
____________________________________________________________
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EIN03- QUESTIONS 19 NOVEMBER 2011 10
Question 4
(a) The figures below are outlines of a three-phase RCD and a 5 pin socket.
Draw and label:
The internal circuit diagram of the three-phase RCD used for personalprotection that protects the 5-pin socket outlet.
The supply to the socket outlet The earthing arrangements
(5 marks)
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Three-phasesocket outlet
Three-phase RCD
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EIN03- QUESTIONS 19 NOVEMBER 2011 11
Question 4 continued
(b) Describe the operation of an RCD when there is an active (phase) to earthfault that occurs on the circuit the RCD protects.
(4 marks)
____________________________________________________________
____________________________________________________________
____________________________________________________________
____________________________________________________________
____________________________________________________________
____________________________________________________________
____________________________________________________________
____________________________________________________________
____________________________________________________________
____________________________________________________________
(c) State TWO types of electrical protection provided by a RCBO.(1 mark)
(1) ________________________________________________________
(2) ________________________________________________________
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EIN03- QUESTIONS 19 NOVEMBER 2011 12
Question 5
(a) The figure below shows a motor control circuit. On the diagram, make theappropriate wiring alterations to connect the remote stop-start and
emergency stop stations.(3 marks)
Note: Indicate the removal of any part of the circuit like this -
(b) A three-phase, 8 kW induction motor connected to a 400 V, 50 Hz, three-phase supply has a power factor of 0.81 and an efficiency of 84% whenfully loaded.
(i) Calculate the input power of the motor. (2 marks)
(turn over)
Remote start stopstation
Emergency stopstation
S1
Overloadcontacts
Stopbutton
Startbutton
M1
D1Timer
P N
M
S
D
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EIN03- QUESTIONS 19 NOVEMBER 2011 13
Question 5 continued
(ii) Calculate the input kVA of the motor.(2 marks)
(iii) Calculate the line current of the motor. (2 marks)
(c) State ONE reason why reduced-voltage starting of a large three-phaseinduction motor may be required.
(1 mark)
____________________________________________________________
____________________________________________________________
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EIN03- QUESTIONS 19 NOVEMBER 2011 14
Question 6
Introduction
The figure below represents a three-phase, star-connected 400V, 15 kWcommercial oven. The elements are of equal resistance.
(a) When the oven was installed, an earth loop impedance test showed a resultof 0.38. The resistance of the protective earthing conductor is 0.1
A high resistance joint of 7.9. has occurred in the protective earthingconductor.
A fault of 2 impedance has developed between L1 and the oven framewhile the oven is operating.
(i) Calculate the total current that will flow in L1 under the faultconditions.
(6 marks)
(turn over)
N
L1
L2
L3
Element 1
Element 2
Element 3
E
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EIN03- QUESTIONS 19 NOVEMBER 2011 15
Question 6 continued
(ii) Calculate the touch voltage that would appear on the frame of theoven
(2 marks)
(b) The oven is protected by 40A HRC fuses with a fusing factor (gG UtilisationCategory) of 1.5.
Use calculations to show why the HRC fuse did not operate when the faultoccurred
(1 marks)
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EIN03- QUESTIONS 19 NOVEMBER 2011 16
Question 7
Introduction
A new single-phase electric hot water cylinder is to be connected to an existingisolating switch in a small factory. The cylinder element is an MIMS type. A newflexible cord has been connected to the cylinder.
The old cylinder has been disconnected and removed.
(a) Two instrument tests need to be carried out to ensure that the hot-watercylinder is safe to connect to the electricity supply.
The only test instrument you have is a multi-function meter with insulationresistance (with 500V and 250V ranges), resistance, voltage andtemperature functions.
(7 marks)
Test 1
For this test:
Name the test. State the meter function selected. State the meter range selected. State how the test is carried out using the function and range
selected.
State an acceptable test result that permits the hot water cylinder tobe connected to the electricity supply.
____________________________________________________________
____________________________________________________________
____________________________________________________________
____________________________________________________________
____________________________________________________________
____________________________________________________________
____________________________________________________________
____________________________________________________________
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EIN03- QUESTIONS 19 NOVEMBER 2011 17
Question 7 continued
Test 2
For this test:
Name the test. State the meter function selected State the meter range selected. State how the test is carried out using the function and range
selected. State an acceptable test result that permits the hot water cylinder to
be connected to the electricity supply.
____________________________________________________________
____________________________________________________________
____________________________________________________________
____________________________________________________________
____________________________________________________________
____________________________________________________________
____________________________________________________________
____________________________________________________________
(b) The cylinder final subcircuit is supplied from a three-phase switchboard andis protected by an HRC fuse.
The isolating switch is not locked nor is it tagged.
Describe the procedure that needs to be followed to ensure personal safetybefore connecting the hot water cylinder to the isolating switch.
(3 marks)
____________________________________________________________
____________________________________________________________
____________________________________________________________
____________________________________________________________
____________________________________________________________
____________________________________________________________
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EIN03- QUESTIONS 19 NOVEMBER 2011 18
Question 8
(a) Explain why rewireable fuses are classed as coarse excess current
protection.
(2 marks)
____________________________________________________________
____________________________________________________________
____________________________________________________________
____________________________________________________________
(b) Explain why HRC fuses and MCBs are classed as close currentprotection.(2 marks)
____________________________________________________________
____________________________________________________________
____________________________________________________________
____________________________________________________________
(c) HRC fuses provide short-circuit and overload protection to a three-phasemotor final subcircuit.
State the main reason why the HRC fuses do not provide overloadprotection for the motor.
(1 mark)
____________________________________________________________
____________________________________________________________
____________________________________________________________
(d) Apart from cost, state TWO technical advantages that HRC fuses havewhen compared to MCBs.
(1 mark)
(1) ________________________________________________________
(2) ________________________________________________________
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EIN03- QUESTIONS 19 NOVEMBER 2011 19
Question 8 continued
(e) Describe the term back-up protection in relation to the protection of finalsubcircuits.
(2 marks)
____________________________________________________________
____________________________________________________________
____________________________________________________________
____________________________________________________________
(f) Describe the term discrimination in relation to electrical protection in anelectrical installation.
(2 marks)
____________________________________________________________
____________________________________________________________
____________________________________________________________
____________________________________________________________
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EIN03- QUESTIONS 19 NOVEMBER 2011 20
Question 9
(a) Sketch and label a simple diagram to represent the neutral and earthingarrangements for an MEN distribution system showing:
A delta-star-connected 11 kV/400 V supply transformer showing theneutral line and earthing arrangements
A single-phase consumer switchboard that shows the neutral andearthing arrangement
A three-phase consumer switchboard that shows the neutral andearthing arrangement
(4 marks)
(b) State TWO factors that determine the prospective short-circuit current inan electrical installation.
(2 marks)
(1) ________________________________________________________
________________________________________________________
(2) ________________________________________________________
________________________________________________________
(turn over)
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EIN03- QUESTIONS 19 NOVEMBER 2011 21
Question 9 continued
(c) Briefly describe how earthing the metal frame of a Class I electricalappliance prevents electric shock hazards under fault conditions.
(2 marks)
____________________________________________________________
____________________________________________________________
____________________________________________________________
(d) An electrical installation has protective devices rated lower than the levelof prospective short-circuit current.
Describe TWO hazardous conditions that could occur in the installationwhen a high current fault occurs.
(2 marks)
(1) ________________________________________________________
________________________________________________________
(2) ________________________________________________________
________________________________________________________
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EIN03 QUESTIONS 19 NOVEMBER 2011
For Candidates Use For Examiners Use OnlyQuestionsAnswered
Marks
1
2
3
4
In the box, write thenumber of EXTRAsheets you haveused. Write NIL ifyou have not usedany
5
6
7
8
9
TOTAL
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