FINAL - EST 2069 - Electrical Service Technician Answer Schedule Notes:1. means that the preceding statement/answer earns 1 mark. 2. This schedule sets out the accepted answers to the examination questions. A marker can exercise their discretion and decide on the overall accuracy of any answer that is presented in the candidate s own words. 3. Symbols and terms - alternatives Power W or P Voltage V or E or U Phase Active Question 1 Marks Reference Marking notes (a) I = V R = 230 24 = 9.58A (b) Any ONE of: A landlord of residential premises must not provide any fittings or appliances under or in connection with a residential tenancy if the fittings or appliances are electrically unsafe. A landlord of residential premises must not allow any person to use any fittings or appliances provided by the landlord under or in connection with a residential tenancy if the fittings or appliances are electrically unsafe. A landlord of residential premises must provide the occupier with adequate instructions for the safe use of any fittings or appliances provided under or in connection with a residential tenancy. ESR 15A(1) ESR 15A(2) ESR 15A(3) (c) Correct circuit connections (polarity) Continuity of conductors (d) Low voltage is any voltage between 50V and 1000V. Standard low voltage is a nominal voltage of 230V between phase and neutral ESR 4 ESR 4 FINAL - EST 2069 ANSWERS 25 JUNE 2016 1
Question 1 Marks Reference Marking notes (e) One pole of the isolating switch has failed to open. (f) (i) 1 MΩ (ii) 1Ω (g) Any TWO of: When the appliance is double insulated When the appliance is supplied from an isolating transformer When connected to a generator supply (h) Open circuited centrifugal switch Open start winding circuit (i) Other equipment could fail or stop during an essential operation (lift or elevator control circuit) (j) Category of duty (Rupturing Capacity) Current rating FINAL - EST 2069 ANSWERS 25 JUNE 2016 2
Question 2 Marks Reference Marking notes (a) Earth continuity test * An ohmmeter * Test between the earth conductor of the flexible cord and the frame of the press. * A test result of 1Ω or less Insulation resistance test * Insulation resistance tester * 500V d.c. * Bridge the phase and neutral on the flexible cord * Test between the bridge and the frame of the press * A test result of 1MΩ or more (b) The description has to show: Taking a voltage test on the load side of the isolator. Using the prove-test-prove method Locking the isolator Attaching a danger tag to the isolator. (c) By testing the resistance between the frame of the printing press and another earth. FINAL - EST 2069 ANSWERS 25 JUNE 2016 3
Question 3 Marks Reference Marking notes (a) (i) 1. Phase 2. Neutral 3. Fuse 4. Start button 5. Hold-in contact 6. Coil 7. Stop button 8. Thermal overload (4 marks) (ii) 24V or 110V or 230V (b) (i) Detects an overload and opens the control circuit. When the current exceeds a pre-determined level. (ii) Detects a rise in temperature in the motor windings. Opens the control circuit when the temperature exceeds a pre-set level. (c) The motor s original direction of rotation will be reversed. FINAL - EST 2069 ANSWERS 25 JUNE 2016 4
Question 4 Marks Reference Marking notes (a) Only the protective device nearest the fault operates. (b) 60A Is the maximum current the fuse can carry continuously 440V is the maximum operating voltage of the fuse AC40. 40,000A is the maximum prospective short circuit current the fuse can safely interrupt (c) To provide short-circuit protection for the motor final subcircuit (d) (i) As current through a protective device increases, the time taken to operate decreases. (ii) FINAL - EST 2069 ANSWERS 25 JUNE 2016 5
Question 5 Marks Reference Marking notes (a) A short-circuit will be created which will operate the meter protection. (b) The voltmeter will show a 0 volt reading even though the circuit being measured is live. (c) Cord extension sets AS/NZS 3760: Appendix F (d) Any TWO of: Ensure the correct instrument for the conditions is used. Inspect instrument, clips, leads and probes to ensure they are in good condition. Ensure correct function is selected on the instrument. Ensure correct range is selected on the instrument. Ensure leads are correctly connected. (e) (i) Any ONE of: Clamped around the phase (active) conductor. Clamped around the neutral conductor. (ii) The current flowing in the phase and neutral are balanced so no reading can be obtained. (f) The output voltage of the ohmmeter is insufficient to stress the insulation. FINAL - EST 2069 ANSWERS 25 JUNE 2016 6
Question 6 Marks Reference Marking notes (a) (i) A degree of protection in accordance with AS 60529. AS/NZS 3000: 1.4.61 Appendix: G1 (ii) The degree of protection against solid objects Protection of persons against access to hazardous parts. AS/NZS 3000: Appendix: G1 AS/NZS 3000: Appendix: G1 (iii) A degree of protection against entry of water with harmful effects. AS/NZS 3000: Appendix: G1 (b) 5 Limited ingress of dust permitted (no harmful deposit). AS/NZS 3000: Table G1(a) X No degree of protection specified. AS/NZS 3000: Appendix G1 (c) Protection by means of obstacles in accordance with clause 1.5.4.5 Protection by placing out of reach in accordance with clause 1.5.4.6 AS/NZS 3000: 6.3.3.1(a) AS/NZS 3000: 6.3.3.1(b) (d) Any TWO of: IPX8 AS/NZS 3000 6.3.4.1(a) Provided with the required degree AS/NZS 3000 of protection 6.3.4.5(a)(ii) Designed and constructed specifically for use in a swimming pool Be rated at a nominal voltage not exceeding 12V a.c. AS/NZS 3000 6.3.4.5(a)(i) AS/NZS 3000 6.3.4.5(a)(iii) FINAL - EST 2069 ANSWERS 25 JUNE 2016 7
Question 7 Marks Reference Marking notes (a) The maximum current a fuse-link can carry continuously. (b) (i) The fuse is under-rated for the circuit. (ii) Any ONE of: The fuse is over-rated for the circuit. The rupturing capacity of the fuse is too small (c) Any TWO of: It prevents the fuse element from bulging out the side of the carrier and being accessible to touch. Under overload conditions the heat produced in the element is confined to the tunnel area. Under short-circuit conditions the arc and molten element is confined within the fuse carrier and base. (d) (i) Detects the loss of voltage on a phase Opens the control circuit and trips out the motor. (ii) Detects the reversal of any two phases of the supply. Prevents the motor from starting (e) The overload causes a bi-metal to heat up and bend, operating a trip mechanism (f) It is the maximum current an MCB can interrupt under fault conditions. FINAL - EST 2069 ANSWERS 25 JUNE 2016 8
Question 8 Marks Reference Marking notes (a) Maintaining contact L O/L M Stop Start Timer Auxiliary Delta S N Timer Auxiliary Star D T Fuse protects entire circuit Overload protects entire circuit Correctly connected stop button Correctly connected start button and hold-in contacts Correctly connected timers Correctly connected delta auxiliary contact Correctly connected star auxiliary contact Correctly connected main contactor coil Correctly connected star contactor coil Correctly connected delta contactor coil Working circuit (b) Any ONE of: The motor ventilation is restricted in some manner. The cooling fan has become detached from the motor shaft FINAL - EST 2069 ANSWERS 25 JUNE 2016 9
(c) (i) Thermistor (ii) In the windings of the motor (d) Interchange two phases on the motor terminal block FINAL - EST 2069 ANSWERS 25 JUNE 2016 10
Question 9 Marks Reference Marking notes (a) R = R 2 x R 3 R 2 + R 3 = 20 x 50 20 + 50 = 14.29Ω R t = 50 + 14.29 = 64.29Ω I = V R = 230 64.29 = 3.58A (b) P = V 2 R = 230 x 230 64.29 = 822.83W P = V 2 R = 230 x 230 70 = 755.71W = 822.83 755.71 = 67.12W FINAL - EST 2069 ANSWERS 25 JUNE 2016 11