EWRB THEORY LATEST 2026 EXAM QUESTIONS AND
SOLUTIONS RATED A+
✔✔Name TWO components that are typically used to smooth the DC output of a
rectifier. - ✔✔ANY TWO:
- Capacitors
- Inductors
- Resistors
- Transistor
- Zener Diode
- Voltage Regulator
✔✔Explain what is meant by the term, INVERSE TIME-CURRENT CHARACTERISTIC
in relation to a protective device. - ✔✔As the current through the protective device
increases, the time taken to operate decreases.
(The larger the current flowing through a protective device, the quicker it will operate).
✔✔State TWO factors that determine the prospective short-circuit current in an
electrical installation. - ✔✔ANY TWO:
- Supply voltage.
- The impedance if the earth fault loop.
- Capacity (kA) of the supply source.
✔✔State EIGHT components of a MEN system that are found in a MEN low voltage
installation. - ✔✔- Main earth bar
- Main earthing conductor
- Earth electrode
- MEN link (connection)
- Main neutral bar
- Main neutral conductor
- Protective earthing conductors
- Equipotential bonding conductors
✔✔State the main function of the main earthing conductor and the earth electrode in a
low voltage, MEN installation. - ✔✔ANY ONE:
- To connect the parts of an installation required to be earthed, to the mass of earth.
- To keep the neutral potential to 0V.
- To keep the phase potential to 230V.
✔✔Explain why Class || (double-insulated) electrical equipment IS NOT required to be
connected to a protective earthing conductor. - ✔✔There is supplementary insulation
between the basic insulation and any metal that could become live under fault
conditions.
, ✔✔Explain how the operation of an AC variable speed controller is different to the
operation of an electronic soft starter. - ✔✔- The variable speed controller varies the
FREQUENCY and voltage to vary the speed.
- The electronic soft start varies voltage on starting to limit the starting CURRENT.
✔✔Explain the term RAMP TIME as it relates to an AC variable speed controller. -
✔✔The adjustment that controls the length of time taken for a change in speed to take
place.
✔✔Define extra-low voltage (ELV). - ✔✔<50V AC or 120V DC.
✔✔Define low voltage. - ✔✔50V - 1200V AC or 120V - 1500V DC.
✔✔Define high voltage. - ✔✔>1000V AC or 1500V DC.
✔✔Explain coarse excess-current protection. - ✔✔When a protection device does NOT
interrupt a fault current within 4 hours when a fault current is 1.5 times that of the rated
current of the protection device.
✔✔Explain close excess-current protection. - ✔✔When a protection device DOES
interrupt a fault current within 4 hours when the fault current is 1.5 times the rated
current of the protection device.
✔✔What is another term for utilisation category? - ✔✔Fusing factor.
✔✔Apart from cost, state TWO technical advantages that HRC fuses have when
compared to MCBs. - ✔✔- Higher kA rating (short circuit protection).
- Faster speed of operation.
✔✔Define the term DISCRIMINATION in relation to electrical protection in an electrical
installation. - ✔✔The protective device CLOSEST to the fault operates before any other
protective device can operate.
✔✔State TWO methods used to cool transformers. - ✔✔ANY TWO:
- Air cooled
- Oil cooled
- Pumped or natural convection
- Forced or natural ventilation
✔✔State the main advantage of a single-phase synchronous motor when compared to
a single-phase induction motor. - ✔✔The synchronous motor rotates at a
constant speed independent of the load.
SOLUTIONS RATED A+
✔✔Name TWO components that are typically used to smooth the DC output of a
rectifier. - ✔✔ANY TWO:
- Capacitors
- Inductors
- Resistors
- Transistor
- Zener Diode
- Voltage Regulator
✔✔Explain what is meant by the term, INVERSE TIME-CURRENT CHARACTERISTIC
in relation to a protective device. - ✔✔As the current through the protective device
increases, the time taken to operate decreases.
(The larger the current flowing through a protective device, the quicker it will operate).
✔✔State TWO factors that determine the prospective short-circuit current in an
electrical installation. - ✔✔ANY TWO:
- Supply voltage.
- The impedance if the earth fault loop.
- Capacity (kA) of the supply source.
✔✔State EIGHT components of a MEN system that are found in a MEN low voltage
installation. - ✔✔- Main earth bar
- Main earthing conductor
- Earth electrode
- MEN link (connection)
- Main neutral bar
- Main neutral conductor
- Protective earthing conductors
- Equipotential bonding conductors
✔✔State the main function of the main earthing conductor and the earth electrode in a
low voltage, MEN installation. - ✔✔ANY ONE:
- To connect the parts of an installation required to be earthed, to the mass of earth.
- To keep the neutral potential to 0V.
- To keep the phase potential to 230V.
✔✔Explain why Class || (double-insulated) electrical equipment IS NOT required to be
connected to a protective earthing conductor. - ✔✔There is supplementary insulation
between the basic insulation and any metal that could become live under fault
conditions.
, ✔✔Explain how the operation of an AC variable speed controller is different to the
operation of an electronic soft starter. - ✔✔- The variable speed controller varies the
FREQUENCY and voltage to vary the speed.
- The electronic soft start varies voltage on starting to limit the starting CURRENT.
✔✔Explain the term RAMP TIME as it relates to an AC variable speed controller. -
✔✔The adjustment that controls the length of time taken for a change in speed to take
place.
✔✔Define extra-low voltage (ELV). - ✔✔<50V AC or 120V DC.
✔✔Define low voltage. - ✔✔50V - 1200V AC or 120V - 1500V DC.
✔✔Define high voltage. - ✔✔>1000V AC or 1500V DC.
✔✔Explain coarse excess-current protection. - ✔✔When a protection device does NOT
interrupt a fault current within 4 hours when a fault current is 1.5 times that of the rated
current of the protection device.
✔✔Explain close excess-current protection. - ✔✔When a protection device DOES
interrupt a fault current within 4 hours when the fault current is 1.5 times the rated
current of the protection device.
✔✔What is another term for utilisation category? - ✔✔Fusing factor.
✔✔Apart from cost, state TWO technical advantages that HRC fuses have when
compared to MCBs. - ✔✔- Higher kA rating (short circuit protection).
- Faster speed of operation.
✔✔Define the term DISCRIMINATION in relation to electrical protection in an electrical
installation. - ✔✔The protective device CLOSEST to the fault operates before any other
protective device can operate.
✔✔State TWO methods used to cool transformers. - ✔✔ANY TWO:
- Air cooled
- Oil cooled
- Pumped or natural convection
- Forced or natural ventilation
✔✔State the main advantage of a single-phase synchronous motor when compared to
a single-phase induction motor. - ✔✔The synchronous motor rotates at a
constant speed independent of the load.
