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

ANSWER: A

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

ANSWER: A

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

ANSWER: A

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

ANSWER: A

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

ANSWER: A

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

ANSWER: A

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

ANSWER: A

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

ANSWER: D

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

ANSWER: A


Last modified: Monday, 31 May 2021, 9:11 PM