Transcript
EAS 1053 Candidate Code No.
For Board Use Only
Result Date Int
Result Date Int
ELECTRICAL APPLIANCE SERVICEPERSON EXAMINATION 19 June 2010 QUESTION AND ANSWER BOOKLET Time Allowed: 2 Hours INSTRUCTIONS – READ CAREFULLY You have 10 minutes to read this paper but do not start writing until instructed to do so by the supervisor. Write your Candidate Code Number in the box provided above. Your name must NOT appear anywhere in 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. Marks are allocated on the basis of correctness. Do not use correcting fluid or correcting tape. Nonprogrammable calculators may be used. It is recommended that the reference source for your answers be included in the space provided if a question can be answered from the Act, Regulations, Standard or Code. However, just stating a reference only will earn no marks. For calculation questions all workings, including formulae, must be shown to gain full marks. Warning – You could get 0 marks for any question, or part of a question, if you show anything hazardous or dangerous in your answer. You may need to use some of the following documents in this examination: ● Electricity Act 1992 reprint dated 19 August 2005 and the Electricity Amendment Act 2006 or Electricity Act 1992 reprint dated 2008 and the Electricity Amendment Act 2006 or the Electricity Act 1992 reprint dated 1 April 2010 ● Electricity Regulations 1997 reprint dated 2 September 2005 or the Electricity (Safety) Regulations 2010 ● AS/NZS 3000:2000 and Amendments 1, 2, 3 and A or AS/NZS 3000:2007 and Amendment No 1 ● AS/NZS 3760:2003 and Amendment No 1 PLEASE HAND THIS PAPER TO THE SUPERVISOR BEFORE LEAVING THE ROOM (turn over)
Question 1 Each part in this question is worth 2 marks. Write the identifying number, 1 or 2 or 3 or 4, for each part in the box provided (a) Registered Electrical Appliance Servicepersons must complete refresher courses at regular intervals. Refer to the Electricity Regulations and state the interval at which the refresher courses must be completed? 1. 15 months 2. 20 months 3. 24 months 4. 12 months (b) A 230V electrical appliance comprises two elements of equal resistance connected in series. What is the voltage drop across one of the elements when the appliance is operating: 1. 230V 2. 400V 3. 75V 4. 115V (c) The term “Class II” on a nameplate of an electrical appliance indicates that the appliance is doubleinsulated. Which one of the following would also indicate that the appliance is doubleinsulated: 1. Class I 2. Allinsulated 3. A square within a square 4. 240V (turn over) EAS 1053 QUESTIONS – 19 JUNE 2010
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Question 1 continued (d) Under which of the following circuit conditions is the thermal mechanism of an MCB specifically designed to operate (trip)? 1. An overload 2. A rise in current of short duration 3. A high motor starting current 4. A shortcircuit (e) An HRC fuse with a Utilisation category (fusing factor) of 1.5 has a minimum fusing current of 30 amps. The current rating of this fuse is: 1. 30A 2. 31.5A 3. 45A 4. 20A (f) The nameplate on the soldering iron states that it operates at 230/240V and is rated at 87 watts. What current will it draw when plugged into a power supply in New Zealand. 1. 0.25A 2. 0.38A 3. 4A 4. 0.38W (turn over) EAS 1053 QUESTIONS – 19 JUNE 2010
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Question 1 continued (g) In accordance with the Electricity Regulations, which of the following voltages is standard low voltage in respect to a single phase MEN system? 1. 120V. 2. 110V. 3. 50V. 4. 230V. (h) When fighting a fire in live electrical equipment, which of the following fire extinguishers should not be used? 1. Water gas expelled 2. Dry powder 3. Vaporising liquid 4. Carbon dioxide (i) What is the power output of a small electric motor with a nameplate that reads: Voltage 230 Phases 1 Horsepower 0.75 Speed 1425 r.p.m. 1. 373.3 watts 2. 375.5 watts 3. 559.5 watts 4. 750.3 watts (turn over) EAS 1053 QUESTIONS – 19 JUNE 2010
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Question 1 continued (j) State the reason why a bayonet cap adaptor must not be used to supply a Class I electrical appliance. 1. Wrong voltage rating 2. It is the wrong colour coding 3. It has no earthing facility 4. The cord supplying the adaptor is the wrong shape (turn over) EAS 1053 QUESTIONS – 19 JUNE 2010
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Question 2 (a) The figure below represents the metal frame of a 230V, Class I, portable appliance. ● Within the frame, draw and label the following components: * A fuse that protects the whole circuit. * A singlepole switch that controls the circuit. * Element 1 is 50Ω and is connected closest to the switch. * Element 2 is 20 Ω and element 3 is 50 Ω. These two elements are connected in parallel after element 1 ● Draw and label the supply to the appliance. (5 marks) Metal frame of the Class I Appliance (turn over) EAS 1053 QUESTIONS – 19 JUNE 2010
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Question 2 continued (b) Calculate the current drawn by the appliance. (5 marks) (turn over) EAS 1053 QUESTIONS – 19 JUNE 2010
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Question 3 Rewireable fuses, HRC fuses and MCBs may be found on switchboards. (a) It is important to replace a blown fuse with one of the correct current rating. What would be the overall effect on a subcircuit if you used a replacement fuse that had: (i) An underrated current rating for the subcircuit it protects? (1 mark) ________________________________________________________ ________________________________________________________ ________________________________________________________ (ii) An overrated current rating for the subcircuit it protects? (1 mark) ________________________________________________________ ________________________________________________________ ________________________________________________________ (b) State THREE advantages that HRC fuses have when compared to rewireable fuses. (3 marks) (1) ________________________________________________________ ________________________________________________________ ________________________________________________________ (2) ________________________________________________________ ________________________________________________________ ________________________________________________________ (3) ________________________________________________________ ________________________________________________________ _______________________________________________________ (turn over) EAS 1053 QUESTIONS – 19 JUNE 2010
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Question 3 continued (c) Briefly state THREE safety reasons why it is not permitted to bridge the terminals of HRC fuse carriers with fuse wire of the same current rating as the blown cartridge. (3 marks) (1) ________________________________________________________ ________________________________________________________ ________________________________________________________ (2) ________________________________________________________ ________________________________________________________ ________________________________________________________ (3) ________________________________________________________ ________________________________________________________ ________________________________________________________ (d) (i) Under which circuit condition is the thermal mechanism of an MCB specifically designed to operate (trip)? (1 mark) ________________________________________________________ (ii) Under which circuit condition is the electromagnetic mechanism of an MCB specifically designed to operate (trip)? (1 mark) ________________________________________________________ (turn over)
EAS 1053 QUESTIONS – 19 JUNE 2010
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Question 4 (a) Two single phase 230V Class II, plugin electrical appliances are each supplied by a flexible cord. (i) Appliance 1 State ONE set of colour coding for the flexible cord. State the polarity for each colour. Note: You must state the colours and polarity accurately. (2 marks) ________________________________________________________ ________________________________________________________ ________________________________________________________ (ii) Appliance 2 State ONE set of colour coding – different from those stated for Appliance 1 for the flexible cord. State the polarity for each colour. Note: You must state the colours and polarity accurately. (2 marks) ________________________________________________________ ________________________________________________________ ________________________________________________________ (b) An electrical appliance is being supplied from a three core flexible extension cord. The extension cord has been disconnected because it started to overheat. State the TWO actions, either of which could be taken to stop this situation reoccurring. (2 marks) (1) ________________________________________________________ ________________________________________________________ (2) ________________________________________________________ ________________________________________________________ (turn over) EAS 1053 QUESTIONS – 19 JUNE 2010
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Question 4 continued (c) If the phrase “it is the maximum current that it is designed to carry safely” is used in respect to a flexible cord, what characteristic is being described? (1 mark) ____________________________________________________________ ____________________________________________________________ (d) The figure below represents the terminals of an appliance plug viewed from the rear after the cover has been removed. Indicate on the figure the active (phase), neutral and earth terminals. Note: You must state the polarity accurately. (3 marks) (turn over) EAS 1053 QUESTIONS – 19 JUNE 2010
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Question 5 You have repaired two 230V, plugin electrical appliances and certain checks and tests are required to be carried in accordance with AS/NZS 3760 on both appliances before they are returned to service. Appliance 1 is a Class I portable oven. You have replaced the mineral insulated metal sheathed (MIMS) element and flexible cord. Appliance 2 is a Class II electrical drill. You have replaced the flexible cord and plug. (a) Refer to AS/NZS 3760 and state the tests that must be carried out on the appliances using test instruments. You must state: ● The type of test carried out. ● The instrument used ● The test voltage, if applicable. ● The permitted test result. ● Whether the test result is a minimum or maximum value. Note: 1. There are no semiconductor devices in either appliance. 2. A PAT or earth leakage tester cannot be used. (7 marks) Appliance 1 ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ Ref: ………………………………………………………… (turn over) EAS 1053 QUESTIONS – 19 JUNE 2010
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Question 5 continued
Appliance 2
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Ref: ……………..………………………………………… (b) Refer to AS/NZS 3760 and describe TWO visual checks (inspections) that need to be carried out on the flexible cord of Appliance 1 (but not the appliance itself) Note: The answers must relate only to Appliance 1 (1 mark) (1) ________________________________________________________ ________________________________________________________ (2) ________________________________________________________ ________________________________________________________ Ref: ……………..………………………………………… (turn over) EAS 1053 QUESTIONS – 19 JUNE 2010 13
Question 5 continued (c) Refer to AS/NZS 3760 and describe TWO visual checks (inspections) that need to be carried out on the Appliance 1 (but not the flexible cord and plug) Note: The answers must relate only to Appliance 1 (1 mark) (1) ________________________________________________________ ________________________________________________________ (2) ________________________________________________________ ________________________________________________________ Ref: ………………………………………………………… (d) Refer to AS/NZS 3760 and describe TWO visual checks (inspections) that need to be carried out on Appliance 2. Note: The answers must relate only to Appliance 2 (1 mark) (1) ________________________________________________________ ________________________________________________________ (2) ________________________________________________________ ________________________________________________________ Ref: ………………………………………………………… (turn over) EAS 1053 QUESTIONS – 19 JUNE 2010
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Question 6 (a) In a singlephase capacitor start motor: (i) How is the start winding disconnected when the motor is up to speed? (1 mark) ________________________________________________________ (ii) Describe how you would reverse the direction of rotation in this type of motor. (1 mark) ________________________________________________________ ________________________________________________________ ________________________________________________________ (iii) What would be the effect on the performance of this singlephase capacitor start motor if the capacitor had become disconnected and the motor was switched on whilst connected to a load? (1 mark) ________________________________________________________ (b) (i) Describe how the direction of rotation can be reversed for a Universal (series) motor (1 mark) ________________________________________________________ ________________________________________________________ ________________________________________________________ (ii) State TWO typical applications for a Universal (series) motor (1 mark) (1) ____________________________________________________ (2) ____________________________________________________ (turn over) EAS 1053 QUESTIONS – 19 JUNE 2010
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Question 6 continued (c) The figure below shows the circuit diagram for a singlephase induction motor at rest. Phase A C B
Neutral (i)
What type of singlephase induction motor is being shown? (1 mark)
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(ii) Name the components shown in the figure: (3 marks)
A
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B
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C
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(iii) Describe how you would reverse the direction of rotation in this type of motor. (1 mark)
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(turn over) EAS 1053 QUESTIONS – 19 JUNE 2010
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Question 7 (a) You have repaired a 230V, Class I electrical appliance and are carrying out the instrument tests required by AS/NZS 3760. You are going to use an ohmmeter to carry out the first test. (i) What type of test are you carrying out using the ohmmeter? (1 mark) ________________________________________________________ (ii) Briefly explain how the test you stated in (a)(i) should be carried out. (2 marks) ________________________________________________________ ________________________________________________________ ________________________________________________________ ________________________________________________________ (iii) (1) What is the permitted resistance for the test you stated in (a)(i)? (1 mark) ____________________________________________________ (2) Is this resistance a minimum or maximum value? (1 mark) ____________________________________________________ (iv) Briefly explain ONE reason for carrying out the test you stated in (a)(i) (1 mark) ________________________________________________________ ________________________________________________________ ________________________________________________________ EAS 1053 QUESTIONS – 19 JUNE 2010
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Question 7 continued (b) Briefly explain why the ohmmeter should not be used to carry out an insulation resistance test on a portable electrical appliance. (2 marks) ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ (c) The second test you will carry out on the 230V, Class I electrical appliance is an insulation resistance test with the appliance disconnected from the electricity supply. (i) What type of test instrument would you use? (1 mark) ________________________________________________________ (ii) What test voltage would you apply? (1 mark) ________________________________________________________ (turn over) EAS 1053 QUESTIONS – 19 JUNE 2010
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Question 8 An ohmmeter is used to measure the resistance of a 230V plugin heater. When connected to the heater's flexible cord plugtop the ohmmeter gives a reading of 24Ω. (a) The heater is plugged into a socket outlet in an electrical installation at a nominal voltage of 230V. The voltagedrop on that socket outlet cannot be more than 5%. Calculated the minimum permitted voltage at the socket outlet. (2 marks) (b) Calculate the power (watts) the heater will consume when operating at the minimum permitted voltage (2 marks) (c) Calculate the power (watts) the heater will consume when operating at 230V. (2 marks) (turn over) EAS 1053 QUESTIONS – 19 JUNE 2010 19
Question 8 continued (d) Calculate the percentage difference in the power consumed between the heater operating at 230V and operating at the minimum permitted voltage. (3 marks) (e) Will the current drawn by the heater increase or decrease when operating at the minimum permitted voltage? (1 mark) ____________________________________________________________ (turn over) EAS 1053 QUESTIONS – 19 JUNE 2010
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Question 9 In an office, a 20A HRC fuse link with a fusing factor of 1.5 protects a final subcircuit consisting of two plug sockets supplying various 230V plugin electrical appliances. The fuselink has blown. When the fuselink is replaced, it blows again when the supply is restored to the circuit. ● The fuselink is correctly rated for the circuit and is not faulty. ● The circuit has been tested and found to be clear of faults. There are TWO possible causes of this fault, one of which requires the use of a test instrument to locate the fault. (a) The first fault (no test instruments required). (i) State the type of fault that has occurred. (1 mark) ________________________________________________________ (ii) State the action you would take to establish the cause of the fault. (2 marks) ________________________________________________________ ________________________________________________________ ________________________________________________________ ________________________________________________________ ________________________________________________________ ________________________________________________________ (iii) State the action taken to fix the fault. (1 mark) ________________________________________________________ ________________________________________________________ ________________________________________________________ (turn over) EAS 1053 QUESTIONS – 19 JUNE 2010
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Question 9 continued (b) The second fault (a test instrument required). (i) State ONE type of fault that has occurred. (1 mark)
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(ii) For the fault you have stated in (b)(i), state the action you would take to establish that this is the cause of the fault. Include in your answer:
● ● ● ●
The type of test The type of test instrument used The test voltage The likely test result if a fault has occurred. (4 marks)
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(iii) State the action taken to fix the fault. (1 mark)
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EAS 1053 QUESTIONS – 19 JUNE 2010
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For Candidate’s Use
For Examiner’s Use Only
Questions Answered
In the box, write the number of EXTRA sheets you have used. Write NIL if you have not used any
Marks
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EAS 1053 QUESTIONS – 19 JUNE 2010
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