Quiz sheet for three phase four wire systems

The correct size of the neutral conductor in a 3 phase 4-wire system supplied with 16 mm2 active conductors is:

A) 16mm2

B) 25mm2

C) 10mm2

D) 6mm2

To comply with AS/NZS 3000, the correct size of the neutral conductor in a 3 phase 4-wire consumers mains supplied with 16 mm2 active conductors is:

A) 16mm2

B) 10mm2

C) 25mm2

D) 6mm2

A three phase star connected switchboard draws a current of 200 amperes per phase. The minimum current carrying capacity of the neutral conductor is: (according to the wiring rules)

A) 200A

B) 300A

C) 100A

D) 70A

The value of the neutral current in a 3 phase unbalanced star connected load is the:

A) phasor sum of the phase currents

B) algebraic sum of the line currents

C) algebraic sum of the phase currents

D) difference of the line currents

If the line currents to a balanced 3 phase load are 10 amperes the neutral current is:

A) 0 Amps

B) 5 Amps

C) 10 Amps

D) 20 Amps

If the neutral connection becomes open circuited on an unbalanced 3 phase load, the neutral current:

A) goes to zero

B) halves

C) remains the same

D) doubles

The purpose of the neutral conductor when a 3 phase supply is connected to an unbalanced load is to:

A) carry out-of-balance currents

B) provide a protective circuit

C) provide an earth point

D) reduce the supply voltage

An open circuit in the neutral to an unbalanced star connected load will cause:

A) a change in both line and phase voltage

B) no change in the line or phase voltage

C) a change in line voltage only

D) a change in phase voltage only

When the neutral connection to a balanced 3 phase load becomes open circuit, the voltage between the load star point and the supply star point is:

A) approximately zero volts

B) equal to the phase voltage D

C) equal to the line voltage

D) between zero and phase voltage