EWRB THEORY EVALUATION TEST EXAM 2026
QUESTIONS AND SOLUTIONS RATED A+
✔✔State the purpose of the slip-rings on a wound rotor induction motor (or slip-ring
motor). - ✔✔To connect the external resistance to the wound motor.
✔✔Calculate the fault current if a short circuit occurs on a 230V final subcircuit with an
earth loop impedance test result of 0.32Ω. - ✔✔718.75A
✔✔MEN switchboards have characteristics that are NOT FOUND on a distribution
board. Name TWO of those characteristics. - ✔✔ANY TWO:
A MEN switchboard:
- Has a MEN link between the neutral and earth busbars.
- Has a connection to earth via an earthing lead to an earth electrode.
- Is electrically closest to the point of supply.
- Can supply to another MEN switchboard.
✔✔Why do three-phase induction motors run smoother and quieter than single-phase
induction motors? - ✔✔They have a constant rotating magnetic field.
✔✔State TWO reasons for using reduced voltage starting for a three-phase induction
motor. - ✔✔ANY TWO:
- Reduced starting current.
- Reducing voltage fluctuation/surges.
- Limiting mechanical shock.
✔✔What is the permitted protective earthing conductor test result for a test between the
earth pin of an appliance supply plug and the earth led accessible metal? - ✔✔1Ω Max
✔✔State the reason why the secondary voltage of a transformer is less at full-load than
at no-load. - ✔✔When current is flowing there is an internal volt drop due to the
impedance of the windings.
✔✔What is the minimum value of the permitted test result for the insulation resistance
test of a three-phase, 400V, mains cable? - ✔✔1MΩ
✔✔What is the maximum value of the permitted test result for an earth leakage test of a
230V, Class 1, plug-in appliance? - ✔✔5mA
✔✔State TWO types of fault that a MCB provides protection for. - ✔✔- Short-Circuit
- Overload
✔✔What type of fault does a RCD provide protection for? - ✔✔Earth Faults
, ✔✔State the full name for a PRCD. - ✔✔Portable Residual Current Device.
✔✔State the full name for a RCBO. - ✔✔Residual Circuit Breaker with Overcurrent
protection.
✔✔State the full name for a SRCD. - ✔✔Socket Residual Circuit Breaker.
✔✔State ONE practical method used to reduce iron losses in the construction of a
transformer. - ✔✔ANY ONE:
- Laminate the iron core.
- Use special types of alloy for the core.
✔✔State TWO methods of reducing the stroboscopic effect of a fluorescent fittings
installed across three-phases. - ✔✔ANY TWO:
- Connect fittings on different phases.
- In double-tube fittings, connect a capacitor in series with one ballast or install lead/lag
fittings.
- Intersperse incandescent lighting with the fluorescent lighting.
✔✔Explain the term SENSITIVITY as it applies to a RCD. - ✔✔Sensitivity is the current
imbalance (earth leakage) required to trip the RCD.
✔✔In a Star connected electrical system, state the angle between line voltage and
phase voltage. - ✔✔30º
✔✔In New Zealand, what type of RCD is required to be voltage dependent? -
✔✔Portable Residual Current Device (PRCD)
✔✔State the maximum residual current rating for a RCD installed in a patient treatment
are. - ✔✔10mA
✔✔State TWO reasons why a RUN CAPACITOR would be fitted to a single-phase,
split-phase induction motor. - ✔✔ANY TWO:
- Quieter running.
- Better running torque.
- Less current draw.
- Increased efficiency.
✔✔Name TWO components that are typically used to smooth the DC output of a
rectifier. - ✔✔ANY TWO:
- Capacitors
- Inductors
- Resistors
QUESTIONS AND SOLUTIONS RATED A+
✔✔State the purpose of the slip-rings on a wound rotor induction motor (or slip-ring
motor). - ✔✔To connect the external resistance to the wound motor.
✔✔Calculate the fault current if a short circuit occurs on a 230V final subcircuit with an
earth loop impedance test result of 0.32Ω. - ✔✔718.75A
✔✔MEN switchboards have characteristics that are NOT FOUND on a distribution
board. Name TWO of those characteristics. - ✔✔ANY TWO:
A MEN switchboard:
- Has a MEN link between the neutral and earth busbars.
- Has a connection to earth via an earthing lead to an earth electrode.
- Is electrically closest to the point of supply.
- Can supply to another MEN switchboard.
✔✔Why do three-phase induction motors run smoother and quieter than single-phase
induction motors? - ✔✔They have a constant rotating magnetic field.
✔✔State TWO reasons for using reduced voltage starting for a three-phase induction
motor. - ✔✔ANY TWO:
- Reduced starting current.
- Reducing voltage fluctuation/surges.
- Limiting mechanical shock.
✔✔What is the permitted protective earthing conductor test result for a test between the
earth pin of an appliance supply plug and the earth led accessible metal? - ✔✔1Ω Max
✔✔State the reason why the secondary voltage of a transformer is less at full-load than
at no-load. - ✔✔When current is flowing there is an internal volt drop due to the
impedance of the windings.
✔✔What is the minimum value of the permitted test result for the insulation resistance
test of a three-phase, 400V, mains cable? - ✔✔1MΩ
✔✔What is the maximum value of the permitted test result for an earth leakage test of a
230V, Class 1, plug-in appliance? - ✔✔5mA
✔✔State TWO types of fault that a MCB provides protection for. - ✔✔- Short-Circuit
- Overload
✔✔What type of fault does a RCD provide protection for? - ✔✔Earth Faults
, ✔✔State the full name for a PRCD. - ✔✔Portable Residual Current Device.
✔✔State the full name for a RCBO. - ✔✔Residual Circuit Breaker with Overcurrent
protection.
✔✔State the full name for a SRCD. - ✔✔Socket Residual Circuit Breaker.
✔✔State ONE practical method used to reduce iron losses in the construction of a
transformer. - ✔✔ANY ONE:
- Laminate the iron core.
- Use special types of alloy for the core.
✔✔State TWO methods of reducing the stroboscopic effect of a fluorescent fittings
installed across three-phases. - ✔✔ANY TWO:
- Connect fittings on different phases.
- In double-tube fittings, connect a capacitor in series with one ballast or install lead/lag
fittings.
- Intersperse incandescent lighting with the fluorescent lighting.
✔✔Explain the term SENSITIVITY as it applies to a RCD. - ✔✔Sensitivity is the current
imbalance (earth leakage) required to trip the RCD.
✔✔In a Star connected electrical system, state the angle between line voltage and
phase voltage. - ✔✔30º
✔✔In New Zealand, what type of RCD is required to be voltage dependent? -
✔✔Portable Residual Current Device (PRCD)
✔✔State the maximum residual current rating for a RCD installed in a patient treatment
are. - ✔✔10mA
✔✔State TWO reasons why a RUN CAPACITOR would be fitted to a single-phase,
split-phase induction motor. - ✔✔ANY TWO:
- Quieter running.
- Better running torque.
- Less current draw.
- Increased efficiency.
✔✔Name TWO components that are typically used to smooth the DC output of a
rectifier. - ✔✔ANY TWO:
- Capacitors
- Inductors
- Resistors
