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EIN01

Candidate Code No.

For Board Use Only

Result

Date

Int

Result

Date

Int

ELECTRICAL INSTALLER THEORYEXAMINATION

20 November 2010

QUESTION AND ANSWER BOOKLETTime 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 NOTappear 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.

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EINO1- QUESTIONS 20 NOVEMBER 2010 2

Question 1

(a) (i) If the voltage and current are known, what TWO other factors arerequired to calculate the power consumed by a three-phase motor?

(1 mark)

________________________________________________________

(ii) What TWO factors are required to calculate the power consumed by asingle-phase electrical appliance?

(1 mark)

________________________________________________________

(b) The direction of rotation of a 230V, single-phase motor has been reversedby:

(i) Reversing the connections to the run winding. What type of single-phase motor is being reversed?

(1 mark)

________________________________________________________

(ii) Reversing the connections to the armature brushes. What type ofsingle-phase motor is being reversed?

(1 mark)

________________________________________________________

(c) One reason the metal frame of a Class I electric motor is earthed is toensure 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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EINO1- QUESTIONS 20 NOVEMBER 2010 3

Question 1 continued

(d) State TWO factors that determine the severity of electric shock upon thehuman body.

(2 marks)

(1) ________________________________________________________

(2) ________________________________________________________

(e) In some electrical installations, some final subcircuits supplying three-phase

loads do not have neutral conductors.

State ONE reason why some final subcircuits supplying three-phase loadsdo not have neutral conductors

(2 marks)

____________________________________________________________

____________________________________________________________

____________________________________________________________

____________________________________________________________

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EINO1- QUESTIONS 20 NOVEMBER 2010 4

Question 1 continued

(f) You have carried out a test on a low voltage final subcircuit in an electricalinstallation. The test result value was 20M.

(i) What type of test has been carried out?( mark)

________________________________________________________

(ii) The test was carried out with a multi-meter that has the requiredfunctions (scales).

(A) What function (scale) was selected on the multi-meter?( mark)

____________________________________________________

(B) What range was selected on the multi-meter?( mark)

____________________________________________________

(iii) What minimum test result would you expect if the final subcircuitincorporated a fixed-wired appliance with MIMS elements?

( mark)

________________________________________________________

(g) State the main reason why interlocks are used in a star/delta starter.(2 marks)

____________________________________________________________

____________________________________________________________

____________________________________________________________

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EINO1- QUESTIONS 20 NOVEMBER 2010 5

Question 1 continued

(h) Calculate the power factor of a small three-phase printing factory withmainly motor loading. Metering instruments have recorded the followinginformation:

Power = 30000W Volts = 406V

Amps = 57A per phase(2 marks)

(i) In relation to HRC fuses:

(i) Define the term cut off time as it applies to HRC fuses.(1 mark)

________________________________________________________

________________________________________________________

(ii) Define the term current rating as it applies to HRC fuses.(1 mark)

________________________________________________________

________________________________________________________

(j) Motor starters incorporate protection against faults.

List TWO types of faults that a motor starter could provide protection for.

(1) ________________________________________________________

(2) ________________________________________________________

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EINO1- QUESTIONS 20 NOVEMBER 2010 6

Question 2

(a) Briefly describe what is meant by the term MEN system

(2 marks)

____________________________________________________________

____________________________________________________________

____________________________________________________________

____________________________________________________________

____________________________________________________________

____________________________________________________________

____________________________________________________________

____________________________________________________________

____________________________________________________________

Ref: .

(b) State TWO reasons why the neutral in the MEN system is multiple-earthed.

(2 marks)

(1) ________________________________________________________

________________________________________________________

(2) ________________________________________________________

________________________________________________________

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EINO1- QUESTIONS 20 NOVEMBER 2010 7

Question 2 continued

(c) Draw a circuit diagram showing three-phase, 4 wire, MEN distribution linessupplying:

A single-phase consumer installation. A three-phase consumer installation.

You need to show for each installation, the main switch, neutral and earthbar connections, MEN link and earth electrode

You do not need to show metering, water heating control and fuses andfinal subcircuit conductors.

Note: It is recommended that you label your diagram.(6 marks)

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EINO1- QUESTIONS 20 NOVEMBER 2010 8

Question 3

The primary of a three phase, delta-star transformer is connected to a three-phase supply.

The secondary line voltage is 400V. The turns ratio is 2859:20. When the transformer is fully loaded, the full load primary line current is

4.37A. Assume that there are no losses in the transformer.

(a) Calculate the primary voltage.(4 marks)

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EINO1- QUESTIONS 20 NOVEMBER 2010 9

Question 3 continued

(b) Calculate the full load kVA rating of the transformer.(2 marks)

(c) Calculate the full load secondary line current.

(2 marks)

(d) When the transformer was tested on full load the single- phase terminal VPH

dropped to 222 volts. Calculate the percentage regulation on thetransformer

(2 marks)

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EINO1- QUESTIONS 20 NOVEMBER 2010 10

Question 4

(a) State the maximum permitted rated residual current of an RCD installedfor:

(i) Personal protection in a domestic installation.(1 mark)

________________________________________________________

(ii) Personal protection in a medical-electrical installation.(1 mark)

________________________________________________________

(iii) The protection of property.

(1 mark)

________________________________________________________

(b) A person is using a Class I electrical appliance supplied from an RCDprotected final subcircuit. An earth leakage fault occurs and earth leakagecurrent flows through the persons body.

Why doesnt the person receive a severe electric shock when the earthleakage current flows through their body?

(1 mark)

____________________________________________________________

____________________________________________________________

(c) A Residual Current Circuit Breaker (RCCB) is installed in a single phasecircuit.

Explain why the RCCB does not operate when there is a short circuitbetween active (phase) and neutral in the single phase circuit?

(2 marks)

____________________________________________________________

____________________________________________________________

____________________________________________________________

____________________________________________________________

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Question 4 continued

(d) (i) What type of RCD is required in New Zealand to be voltage dependent.

(1 mark)

________________________________________________________

(ii) Briefly explain why the type of RCD you have stated in (d)(i) isrequired to be voltage dependent.

(1 mark)

________________________________________________________

________________________________________________________

________________________________________________________

________________________________________________________

(e) The phase and neutral on the supply side of a single phase RCD have been

transposed.

Would the RCD operate if it detected an earth leakage fault on the circuit it

protects? State a reason to support your answer.(1 mark)

____________________________________________________________

____________________________________________________________

____________________________________________________________

____________________________________________________________

(f) State the full names for the following terms:(1 mark)

RCBO ____________________________________________________

____________________________________________________

SRCD ____________________________________________________

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EINO1- QUESTIONS 20 NOVEMBER 2010 12

Question 5

Note: Read the entire question before answering (a), (b) and (c).

A three-phase fixed-wired induction motor running an industrial refrigeration

plant is protected by HRC fuses mounted on a switchboard. The motor requiresnew bearings.

The motor is controlled by an adjacent isolating switch. However, the switch hasa broken operating handle and cannot be used.

You have been requested to:

Remove the three-phase motor, by disconnecting the cable at the motor Replace the isolating switch.

Warning: If any part of your answer is dangerous or hazardous, youwill get no marks for this question.

(a) Describe how you would safely isolate the motor and its isolating switch.(6 marks)

(1) ________________________________________________________

________________________________________________________

________________________________________________________

________________________________________________________

(2) ________________________________________________________

________________________________________________________

________________________________________________________

________________________________________________________

(3) ________________________________________________________

________________________________________________________

________________________________________________________

________________________________________________________

(4) ________________________________________________________

________________________________________________________

________________________________________________________

________________________________________________________

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Question 5 continued

(b) After you have done the isolation and the work, what would you do to

ensure that the work area is safe to be left unattended?(3 marks)

(1) ________________________________________________________

________________________________________________________

________________________________________________________

________________________________________________________

(2) ________________________________________________________

________________________________________________________

________________________________________________________

________________________________________________________

(c) State the first action the other electrician should take before attempting tore-install the motor.

(1 mark)

____________________________________________________________

____________________________________________________________

____________________________________________________________

____________________________________________________________

____________________________________________________________

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Question 6

Note: Read the entire question before answering (a) and (b).

Another electrical installer has isolated, disconnected and repaired a 400V three-

phase circular saw in a joinery factory. You are required to:

Reconnect the machine by connecting the flexible cord to the DOL (direct-on-line) starter mounted on an adjacent pillar, and

Recommission the circular saw

There are no danger tags or lock attached to the isolator controlling the DOLstarter. The isolator has a locking facility.

The only test instrument you have is a multi-meter that has all the requiredfunctions (scales).

(a) (i) State the TWO instrument tests you would carry out to ensure the

circular saw is safe to connect to the supply.(1 mark)

Test No. 1 ____________________________________________

Test No. 2 ____________________________________________

(ii) Test No. 1

For this test state:

The function (scale) on the multi-meter you would select. The test voltage (if applicable) The range on the multi-meter you would select. How the test is carried out with the function and range that have

been selected. The expected test result.

(3 marks)

________________________________________________________

________________________________________________________

________________________________________________________

________________________________________________________

________________________________________________________

________________________________________________________

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EINO1- QUESTIONS 20 NOVEMBER 2010 15

Question 6 continued

(iii) Test No. 2

For this test state:

The function (scale) on the multi-meter you would select. The test voltage (if applicable) The range on the multi-meter you would select. How the test is carried out with the function and range that have

been selected. The expected test result.

(3 marks)

________________________________________________________

________________________________________________________

________________________________________________________

________________________________________________________

________________________________________________________

________________________________________________________

(b) You have reconnected the circular saw to the DOL starter. An instrumenttest needs to be carried out to verify that the saw is connected to theinstallations earthing system (that is, the saw is functionally earthed).

For this test state:

The function (scale) on the multi-meter you would select. The range on the multi-meter you would select. How the test is carried out with the function and range that have been

selected. The expected test result.

(3 marks)

____________________________________________________________

____________________________________________________________

____________________________________________________________

____________________________________________________________

____________________________________________________________

____________________________________________________________

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Question 7

(a) The figure below represents the metal frame of a 230V, Class I, portableappliance.

Within the frame, draw and label the following components:

* A fuse that protects the whole circuit.* A single-pole switch that controls the circuit.* Element 1 is 50 and is connected closest to the switch.* Element 2 is 20 and element 3 is 50 . These two elements

are connected in parallel after element 1

Show the supply to the appliance and on to the components.(5 marks)

Metal frame of the Class I Appliance

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Question 7 continued

(b) Calculate the current drawn by the appliance.(5 marks)

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Question 8

The figure below is the nameplate of a motor.

(a) From the information on the nameplate, state the power factor of the

motor.( mark)

____________________________________________________________

(b) Using the information on the nameplate, calculate the output kilowatt

rating of the motor (1 marks)

(c) Using the information on the nameplate, calculate the full load inputkilowatts of the motor

(2 marks)

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Ins.

Type MOT 112M Year.No. 1996042657

kW HzH.P

505.36

R.P.M

1440 Ph.

F3 -

Amb. Temp %.Cos 0.82

Duty S1 Protection. IP 53

V 415

A 8.52

V

A

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Question 8 continued

(d) The motor has a protection rating of IP 53.

(i) What does the term IP mean?

(1 mark)

________________________________________________________

________________________________________________________

(ii) What type of protection is indicated by the first number?(1 mark)

________________________________________________________

________________________________________________________

(iii) What type of protection is indicated by the second number?(1 mark)

________________________________________________________

________________________________________________________

(e) What would be the typical connection for a three-phase, 400V, 20kWmotor?

(1 mark)

____________________________________________________________

(f) The motor is to be started direct on-line and protected by a thermaloverload unit and HRC fuses. The thermal overload unit is incorporated inthe DOL starter protects the motor from overloads.

Briefly explain the term overload as it relates to the thermal overload.(2 marks)

____________________________________________________________

____________________________________________________________

____________________________________________________________

____________________________________________________________

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EINO1- QUESTIONS 20 NOVEMBER 2010 20

Question 9

(a) You need to take a three-phase, 10 kW pump motor away for repair. Youhave isolated the motor and have disconnected the motor cables. Themotor cables are still connected to the DOL starter.

State TWO precautions which must be taken to ensure the safety ofpersons and property after you have completed the isolation and

disconnection(2 marks)

(1) ________________________________________________________

________________________________________________________

________________________________________________________

(2) ________________________________________________________

________________________________________________________

________________________________________________________

(b) How is isolating a 10 kW pump motor different from just switching off10 kW pump motor?

(3 marks)

____________________________________________________________

____________________________________________________________

____________________________________________________________

____________________________________________________________

____________________________________________________________

____________________________________________________________

____________________________________________________________

____________________________________________________________

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EINO1- QUESTIONS 20 NOVEMBER 2010 21

Question 9 continued

(c) You have isolated a 10 kW pump motor.

Describe THREE different methods of safely ensuring the continued

isolation of the pump motor.(3 marks)

(1) ________________________________________________________

________________________________________________________

________________________________________________________

(2) ________________________________________________________

________________________________________________________

________________________________________________________

(3) ________________________________________________________

________________________________________________________

________________________________________________________

(d) State the TWO reasons why the prove test prove method of testing forisolation is used.

(2 marks)

(1) ________________________________________________________

________________________________________________________

________________________________________________________

(2) ________________________________________________________

________________________________________________________

________________________________________________________

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EINO1 QUESTIONS 20 NOVEMBER 2010 22

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 used

any

5

6

7

8

9

TOTAL