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EWRB Theory Exam exam with complete solutions 2024_2025
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EWRB Theory Exam exam with complete solutions 2024_2025
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EWRB Theory Exam exam with completesolutions 2024/2025
What is the minimum value of the permitted test result for the insulation
resistance test of a three-phase, 400V, mains cable? - ANSWER-1MΩ
When carrying out testing on a low voltage electrical installation, which
document details the tests and checks required to be carried out? - ANSWER-
AS/NZS 3000
What is the minimum or maximum test result value you would consider
acceptable for an Earth Continuity test? - ANSWER-1Ω or less
State TWO types of electrical protection provided by a RCBO. - ANSWER-ANY
TWO:
- Earth Leakage
- Overload
- Short Circuit
If the voltage and current are known, what TWO other factors are
required to calculate the power consumed by a three-phase motor? -
ANSWER-√3 & Power Factor
What type of single-phase motor can be reversed by reversing the connections to
the run winding? - ANSWER-ANY ONE:
- Split-Phase Motor
- Capacitor Start Motor
- Cap-Start, Cap-Run Motor
, What type of single-phase motor can be reversed by reversing the connections to
the armature brushes? - ANSWER-ANY ONE:
- Universal Motor
- Series Motor
State ONE reason why the metal frame of a Class 1 electrical appliance is earthed.
- ANSWER-ANY ONE:
- To ensure the operation of a protective device under fault conditions.
- To keep the frame of the appliance at earth potential under fault conditions.
State TWO factors that determine the severity of electric shock upon the human
body. - ANSWER-ANY TWO:
- Voltage Applied
- Shock Current Level
- Contact Duration
- Skin Dryness
- Current Path
You have carried out a test on a low voltage final subcircuit in an electrical
installation, the result value was 20MΩ. What type of test has been carried out? -
ANSWER-Insulation Resistance Test
State the main reason why interlocks are used in a star/delta starter. - ANSWER-
To prevent the star and delta contractors closing simultaneously - and causing a
short circuit.
Calculate the power factor of a small three-phase printing factory with mainly
motor loading. Metering instruments have recorded the following:
Power = 30000W
Voltage = 406V
Current = 57A per phase - ANSWER-0.748
pf = P/V×I×√3
Define the term CUT OFF TIME as it refers to HRC fuses. - ANSWER-ANY ONE:
- Pre-arcing Time: Time taken to melt the fuse elements.
- Arcing Time: The time taken between the initiation of the arc, and the arc
extinguishing.
- Cut Off Current: The fault current that will cause the fuse to blow.
- Total Clearing Time: The time it takes to interrupt the flow of current and
extinguish the flame.
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