EWRB Theory Exam Preparation – Electrical Licensing Concepts –
study guide
What is the minimum value of the permitted test result for the insulation resistance test of a three-
phase, 400V, mains cable? - CORRECT ANSWER ✔✔1MΩ
When carrying out testing on a low voltage electrical installation, which document details the tests and
checks required to be carried out? - CORRECT ANSWER ✔✔AS/NZS 3000
What is the minimum or maximum test result value you would consider acceptable for an Earth
Continuity test? - CORRECT ANSWER ✔✔1Ω or less
State TWO types of electrical protection provided by a RCBO. - CORRECT 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? - CORRECT ANSWER ✔✔√3 & Power Factor
What type of single-phase motor can be reversed by reversing the connections to the run winding? -
CORRECT 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? - CORRECT ANSWER ✔✔ANY ONE:
- Universal Motor
- Series Motor
, State ONE reason why the metal frame of a Class 1 electrical appliance is earthed. - CORRECT 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. - CORRECT
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? - CORRECT ANSWER ✔✔Insulation Resistance
Test
State the main reason why interlocks are used in a star/delta starter. - CORRECT 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 - CORRECT ANSWER ✔✔0.748
pf = P/V×I×√3
Define the term CUT OFF TIME as it refers to HRC fuses. - CORRECT 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.
study guide
What is the minimum value of the permitted test result for the insulation resistance test of a three-
phase, 400V, mains cable? - CORRECT ANSWER ✔✔1MΩ
When carrying out testing on a low voltage electrical installation, which document details the tests and
checks required to be carried out? - CORRECT ANSWER ✔✔AS/NZS 3000
What is the minimum or maximum test result value you would consider acceptable for an Earth
Continuity test? - CORRECT ANSWER ✔✔1Ω or less
State TWO types of electrical protection provided by a RCBO. - CORRECT 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? - CORRECT ANSWER ✔✔√3 & Power Factor
What type of single-phase motor can be reversed by reversing the connections to the run winding? -
CORRECT 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? - CORRECT ANSWER ✔✔ANY ONE:
- Universal Motor
- Series Motor
, State ONE reason why the metal frame of a Class 1 electrical appliance is earthed. - CORRECT 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. - CORRECT
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? - CORRECT ANSWER ✔✔Insulation Resistance
Test
State the main reason why interlocks are used in a star/delta starter. - CORRECT 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 - CORRECT ANSWER ✔✔0.748
pf = P/V×I×√3
Define the term CUT OFF TIME as it refers to HRC fuses. - CORRECT 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.
