7/27/2019 EIN02 Questions 18 June 2011

1/22

EIN02

Candidate Code No.

For Board Use Only

Result

Date

Int

Result

Date

Int

ELECTRICAL INSTALLER THEORYEXAMINATION

18 June 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)

7/27/2019 EIN02 Questions 18 June 2011

2/22

EIN02- QUESTIONS 18 June 2011 2

Question 1

(a) An electrical installer used a voltmeter to test for isolation on the supplyside of a three-phase isolator using the following procedure:

A test on an independent live source confirmed that the meter workedcorrectly.

A test between each phase showed no reading on the meter. Another test on an independent live source confirmed that the meter

still worked correctly.

The installer proceeded to dismantle the isolator and received an electricshock. Explain why the electrical installer received the shock.

(2 marks)

____________________________________________________________

____________________________________________________________

____________________________________________________________

____________________________________________________________

(b) Name FOUR types of protection that a direct-on-line (DOL) motor startermay provide for a three-phase motor.

(2 marks)

(1) ________________________________________________________

(2) ________________________________________________________

(3) ________________________________________________________

(4) ________________________________________________________

(turn over)

7/27/2019 EIN02 Questions 18 June 2011

3/22

EIN02- QUESTIONS 18 June 2011 3

Question 1 continued

(c) In relation to HRC fuses:

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

________________________________________________________

________________________________________________________

(ii) Define the term total clearing time as it applies to HRC fuses.(1 mark)

________________________________________________________

________________________________________________________

(d) A three-phase final subcircuit has heating loads that draw different valuesof current on each of the phases.

State ONE reason why a neutral conductor is required in the finalsubcircuit.

(2 marks)

____________________________________________________________

____________________________________________________________

____________________________________________________________

____________________________________________________________

(e) State the TWO technical factors that will determine the size of a cable usedto supply a three-phase induction motor.

(2 marks)

(1) ________________________________________________________

(2) ________________________________________________________

(turn over)

7/27/2019 EIN02 Questions 18 June 2011

4/22

EIN02- QUESTIONS 18 June 2011 4

Question 1 continued

(f) A three-phase motor has:

Six terminals on the terminal block there are no links. A six-core and earth flexible cable is connected to the terminal block.

To what type of motor starter should the three-phase motor be connected?(2 marks)

____________________________________________________________

(g) An RCD (residual current device) protects a circuit and a fixed-wired Class Ielectrical appliance. The RCD has operated.

What condition has caused the RCD to operate?(2 marks)

____________________________________________________________

____________________________________________________________

____________________________________________________________

____________________________________________________________

(h) (i) What device is used to provide starting torque in a shaded pole motor?(1 mark)

________________________________________________________

(ii) Describe how a shaded pole motor can be reversed.(1 mark)

________________________________________________________

(turn over)

7/27/2019 EIN02 Questions 18 June 2011

5/22

EIN02- QUESTIONS 18 June 2011 5

Question 1 continued

(i) A 230V plug-in heater is designed for use on 230V/240V supply.

When an ohmmeter is used to measure the resistance of the heater, itgives a reading of 24 ohms.

What value of current would the heater draw if it is plugged into a 240Va.c. supply?

(2 marks)

(j) State ONE reason why the multiple earth neutral (MEN) system of supply isused in New Zealand?

(2 marks)

____________________________________________________________

____________________________________________________________

____________________________________________________________

____________________________________________________________

(turn over)

7/27/2019 EIN02 Questions 18 June 2011

6/22

EIN02- QUESTIONS 18 June 2011 6

Question 2

A three-phase star-connected pottery kiln draws 25A from a 400V supply and isprotected by 30A HRC fuses.

(a) A fault of 7 has developed between the red phase and the kiln frame whilethe kiln is operating.

The protective earth conductor resistance to the kiln is 0.5.

(i) Calculate the total current in the red phase.(2 marks)

(ii) Determine, using calculations, whether the 30A HRC fuse on the redphase will operate.

The 30A HRC fuse has a fusing factor (gG Utilisation Category) of 1.5.(2 marks)

(turn over)

7/27/2019 EIN02 Questions 18 June 2011

7/22

EIN02- QUESTIONS 18 June 2011 7

Question 2 continued

(b) On a separate occasion a fault of 7 has developed between the blue phaseand the kiln frame while the kiln is operating

The protective earth conductor resistance to the kiln is 12.

(i) Calculate the total current in the blue phase(2 marks)

(ii) Determine, using calculations, why the 30A HRC fuse in the bluephase may take a long time to operate.

The 30A HRC fuse has a fusing factor (gG Utilisation Category) of 1.5.

(1 mark)

(iii) Determine, using calculations, the electrical shock hazard voltage theprotective earthing conductor resistance of 12 presents to the userof the kiln.

(2 marks)

(turn over)

7/27/2019 EIN02 Questions 18 June 2011

8/22

EIN02- QUESTIONS 18 June 2011 8

Question 3

(a) (i) State TWO advantages of a MCB (miniature circuit breaker) whencompared to a HRC fuse of the same current rating

(1 mark)

(1) ____________________________________________________

____________________________________________________

(2) ____________________________________________________

____________________________________________________

(ii) State TWO disadvantages of a MCB (miniature circuit breaker) when

compared to a HRC fuse of the same current rating(1 mark)

(1) ____________________________________________________

____________________________________________________

(2) ____________________________________________________

____________________________________________________

(iii) State TWO advantages of a HRC fuse when compared to a MCB(miniature circuit breaker) of the same current rating

(1 mark)

(1) ____________________________________________________

____________________________________________________

(2) ____________________________________________________

____________________________________________________

(iv) State TWO disadvantages of a HRC fuse when compared to a MCB(miniature circuit breaker) of the same current rating

(1 mark)

(1) ____________________________________________________

____________________________________________________

(2) ____________________________________________________

____________________________________________________

(turn over)

7/27/2019 EIN02 Questions 18 June 2011

9/22

EIN02- QUESTIONS 18 June 2011 9

Question 3 continued

(b) Briefly state TWO reasons why fuse wire of the same current rating mustnot be used bridge the terminals of HRC fuse carriers.

(2 marks)

(1) ________________________________________________________

________________________________________________________

________________________________________________________

(2) ________________________________________________________

________________________________________________________

________________________________________________________

(c) Explain the internal operation of a MCB (miniature circuit breaker) when thefollowing situations occur.

(i) Overload(2 marks)

________________________________________________________

________________________________________________________

________________________________________________________

________________________________________________________

(ii) Short circuit(2 marks)

________________________________________________________

________________________________________________________

________________________________________________________

________________________________________________________

(turn over)

7/27/2019 EIN02 Questions 18 June 2011

10/22

EIN02- QUESTIONS 18 June 2011 10

Question 4

An old three-phase electric hot water cylinder in a milking shed is to beremoved.

The cylinder is protected by HRC fuses on a three-phase switchboard and alockable isolating switch is located adjacent to the cylinder.

(a) (i) You have been requested to disconnect the wiring at the existingcylinder, but leave the wiring in place.

Describe how you will isolate the cylinder and wiring to ensure it issafe to disconnect.

(4 marks)

________________________________________________________

________________________________________________________

________________________________________________________

________________________________________________________

________________________________________________________

________________________________________________________

________________________________________________________

________________________________________________________

(ii) The isolation has been completed.

State the action taken to ensure that the work area is safe to be leftunattended?

(3 marks)

________________________________________________________

________________________________________________________

________________________________________________________

________________________________________________________

________________________________________________________

________________________________________________________

(turn over)

7/27/2019 EIN02 Questions 18 June 2011

11/22

EIN02- QUESTIONS 18 June 2011 11

Question 4 continued

(b) At a later date a new cylinder will be installed in the same position andreconnected to the existing wiring by another electrical installer.

(i) State the action the other electrical installer should take beforeattempting to install the replacement hot water cylinder.

(2 marks)

________________________________________________________

________________________________________________________

________________________________________________________

________________________________________________________

(ii) List the TWO tests using test instruments that the other electricalinstaller must carry out to ensure the new hot water cylinder is safe toconnect to the electricity supply.

(1 mark)

(1) ____________________________________________________

(2) ____________________________________________________

(turn over)

7/27/2019 EIN02 Questions 18 June 2011

12/22

EIN02- QUESTIONS 18 June 2011 12

Question 5

A three phase 400V induction industrial motor saw is controlled by a star-deltastarter with a 230V control circuit.

The motor has been removed from the machine for cleaning and repair and isready for reconnection. The cable connecting the motor to the starter isconnected to the motor.

(a) A multi-function test instrument with insulation resistance; resistance; andvoltage functions is the only instrument you have available.

(i) State the TWO instrument tests you should carry out to ensure themotor 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 selected on the multi-function test instrument. The range selected on the multi-function test instrument

How the test is carried out using the function and range selected. An acceptable test result.

(3 marks)

________________________________________________________

________________________________________________________

________________________________________________________

________________________________________________________

________________________________________________________

________________________________________________________

(turn over)

7/27/2019 EIN02 Questions 18 June 2011

13/22

EIN02- QUESTIONS 18 June 2011 13

Question 5 continued

(iii) Test No. 2

For this test state:

The function selected on the multi-function test instrument. The range selected on the multi-function test instrument How the test is carried out using the function and range selected. An acceptable test result.

(3 marks)

________________________________________________________

________________________________________________________

________________________________________________________

________________________________________________________

________________________________________________________

________________________________________________________

(b) You have reconnected the motor saw to the star-delta starter. A multi-function test instrument with insulation resistance; resistance; and voltagefunctions is the only instrument you have available.

An instrument test needs to be carried out to verify that the saw isconnected to the installations earthing system (that is, the saw is

functionally earthed).

For this test state:

The function selected on the multi-function test instrument. The range selected on the multi-function test instrument How the test is carried out using the function and range selected. The acceptable test result.

(3 marks)

____________________________________________________________

____________________________________________________________

____________________________________________________________

____________________________________________________________

____________________________________________________________

____________________________________________________________

(turn over)

7/27/2019 EIN02 Questions 18 June 2011

14/22

EIN02- QUESTIONS 18 June 2011 14

Question 6

The figure below is the nameplate of a motor.

(a) State the power factor of the motor.( mark)

____________________________________________________________

(b) Calculate the output kilowatt rating of the motor(1 marks)

(c) Calculate the full load input kilowatts of the motor(2 marks)

(turn over)

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

7/27/2019 EIN02 Questions 18 June 2011

15/22

EIN02- QUESTIONS 18 June 2011 15

Question 6 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, 20kW

motor?(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 and protects the motor from overloads.

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

____________________________________________________________

____________________________________________________________

____________________________________________________________

____________________________________________________________

(turn over)

7/27/2019 EIN02 Questions 18 June 2011

16/22

EIN02- QUESTIONS 18 June 2011 16

Question 7

(a) Danger tags and out-of-service tags are designed to promote safety in theworkplace.

(i) Give a brief description of circumstances when a Danger Tag is used.(1 mark)

________________________________________________________

________________________________________________________

________________________________________________________

(ii) Give a brief description of circumstances when an Out-of-Service

Tag is used.(1 mark)

________________________________________________________

________________________________________________________

________________________________________________________

(iii) List THREE precautions to be taken when attaching a Danger Tag to

an isolating switch.(3 marks)

(1) ____________________________________________________

____________________________________________________

(2) ____________________________________________________

____________________________________________________

(3) ____________________________________________________

____________________________________________________

(turn over)

7/27/2019 EIN02 Questions 18 June 2011

17/22

EIN02- QUESTIONS 18 June 2011 17

Question 7 continued

(b) Explain the difference between:

A 10 kW pump motor that has been isolated.and A 10 kW pump motor that has been switched off.

(3 marks)

____________________________________________________________

____________________________________________________________

____________________________________________________________

____________________________________________________________

____________________________________________________________

____________________________________________________________

____________________________________________________________

____________________________________________________________

(c) Describe how the prove-test-prove method of testing is carried out.

(1 marks)

____________________________________________________________

____________________________________________________________

____________________________________________________________

____________________________________________________________

____________________________________________________________

(d) You are using the prove-test prove method at the supply side of a three-phase main switch to see if the switchboard is isolated. What tests wouldyou make to clearly establish that isolation (or otherwise) has taken place.

( mark)

____________________________________________________________

____________________________________________________________

(turn over)

7/27/2019 EIN02 Questions 18 June 2011

18/22

EIN02- QUESTIONS 18 June 2011 18

Question 8

(a) The three phase low voltage supply to a factory is required to be at avoltage that is not standard low voltage.

The factory is supplied by a 150 kVA three phase, delta-star connectedtransformer with a phase ratio of 47.8 to 1. The primary is connected to an11kV three phase supply and the transformer is fully loaded.

(i) Calculate the secondary phase voltage.(2 marks)

(ii) Calculate the secondary line voltage.(2 marks)

(iii) Calculate the primary line current.(2 marks)

(turn over)

7/27/2019 EIN02 Questions 18 June 2011

19/22

EIN02- QUESTIONS 18 June 2011 19

Question 8 continued

(iv) Calculate the secondary line current.(2 marks)

(b) How is the output of a transformer rated?(1 mark)

____________________________________________________________

(c) State TWO typical configurations found in transformers.(1 mark)

(1) ________________________________________________________

(2) ________________________________________________________

(turn over)

7/27/2019 EIN02 Questions 18 June 2011

20/22

EIN02- QUESTIONS 18 June 2011 20

Question 9

A new three-phase water heater has been installed in an industrial installation toreplace an existing water heater. It has three elements rated at 400V, each with

a resistance of 30. The elements can be connected either in star or delta.

No changes will be made to the circuit supplying the new water heater.

(a) (i) Calculate the line current drawn when the elements are connectedin star.

(2 marks)

(ii) Calculate the line current drawn when the elements are connectedin delta.

(3 marks)

(iii) The circuit is protected by 10A rewireable fuses. In relation to theelectrical protection, state which connection arrangement is mostsuitable for this installation.

( mark)

________________________________________________________

(turn over)

7/27/2019 EIN02 Questions 18 June 2011

21/22

EIN02- QUESTIONS 18 June 2011 21

Question 9 continued

(b) (i) Calculate thepower consumed by the water heater when the elementsare connected in star.

(2 marks)

(ii) Calculate the power consumed by the water heater when the elementsare connected in delta

(1 mark)

(iii) Calculate the difference in the power consumed by the water heater

when the elements are connected in star compared to when theelements are connected in delta(1 mark)

7/27/2019 EIN02 Questions 18 June 2011

22/22

EIN02 QUESTIONS 18 J 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