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AC THEORY PRACTICE QUESTIONS & ANSWERS SCORED A+
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AC THEORY PRACTICE QUESTIONS & ANSWERS SCORED A+
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AC THEORYPRACTICE
QUESTIONS &
ANSWERS
SCORED A+
Evatee 10/5/24 AC THEORY
,AC THEORY PRACTICE QUESTIONS &
ANSWERS SCORED A+
In New Zealand, the standard distribution system has the neutral conductor
connected to the earth at the main switchboard on all low voltage installations.
What name is given to this type of system? Answer - Multiple Earthed Neutral
or MEN system.
State the test voltage used for carrying out an insulation resistance test on
three-phase, 400V, electrical equipment incorporating MIMS elements. Answer
- 500 V d.c.
State the minimum permitted test result for the insulation resistance test on
electrical equipment without MIMS elements Answer - 1MΩ
State the permitted test result for an insulation resistance test for the electrical
installation with all the permanently-connected electrical equipment
connected. Answer - 0.01MΩ
State the minimum permitted test result for the insulation resistance test on
the electrical equipment incorporating MIMS elements. Answer - 0.01MΩ
State ONE precaution that could be taken when using an insulation resistance
tester, set on the 500V d.c. range, to carry out an insulation resistance test on
electrical equipment containing semi-conductor devices. Answer - Bridge out
between phase and neutral
,why you would take this precaution on electrical equipment containing semi-
conductor devices. Answer - The voltage of the test instrument may damage
semi-conductor devices.
AS/NZS 3000 requires that a test voltage of 500V d.c. is used for an insulation
resistance test of a low voltage electrical installation. State ONE reason why the
voltage is a d.c. voltage. Answer - Any ONE of:
● To ensure capacitive or inductive reactance does not influence the test
result.
● A constant maximum voltage is a more
stringent test than the momentary peaks of an a.c. waveform.
AS/NZS 3000 requires that a test voltage of 500V d.c. is used for an insulation
resistance test of a low voltage electrical installation. Explain why a voltage of
500V is applied. Answer - To stress the insulation at a voltage
above 325V a.c. (or peak a.c. voltage).
Tests have been carried out on a three-phase 400V, Class I, plug-in electrical
appliance after it has been repaired. The test results are as follows:
Earth continuity test - out of range
Insulation resistance test - Infinity
What type of fault is indicated by the test results? Answer - Any ONE of:
, ● A high-resistance joint in the
protective earthing circuit.
● An open-circuit in the protective
earthing conductor.
State THREE actions that need to be taken to ensure the electrical appliance is
safe to return to service. Include acceptable test results in the answer. Answer
- ● Repair faulty protective earthing conductor circuit
● Conduct an earth continuity test To ensure the resistance is 1Ω or less
● Any ONE of:
● Conduct an insulation
resistance test. To ensure the insulation
resistance is 1MΩ or more.
● Conduct an earth leakage
test. To ensure that the leakage does not exceed 5 mA.
Define the term impedance as it applies to an a.c. circuit. Answer - It is the
total opposition in Ω (ohms) to the current flow in an a.c. circuit.
Impedance is comprised of three components. State TWO of those
components. Answer - Any TWO of:
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