## Quiz sheet for three phase systems

Normal phase sequence is represented by:

A) ABC

B) CBA

C) BAC

D) ACB

ANSWER: A

One advantage of a three phase supply over single phase is that:

A) 3 phase machines are physically smaller for a given output

B) Three phase machines don't require an earth

C) 3 phase voltages are lower than single phase

D) single phase motors have constant torque

ANSWER: A

The angle between phase windings in a 3 phase alternator is:HINT

A) 120°

B) 180°

C) 90°

D) 60°

ANSWER: A

The colours typically used to represent the 3 phases of a 3 phase system are:

A) Red White Blue

B) Red White Black

C) Red Yellow Black

D) Red Yellow Blue

ANSWER: A

Three phase alternator windings are normally connected in:HINT

A) star

B) series

C) delta

D) zigzag

ANSWER: A

The order in which the phases of a 3 phase supply reach their maximum value is known as the:

A) phase sequence

B) phase order

C) supply sequence

D) voltage sequence

ANSWER: A

The usual method of reversing the order in which phases in a 3 phase supply reach theft maximum value is to:

A) interchange two connections

B) end for end the rotor

C) reverse one winding

D) reverse the rotation of the prime mover

ANSWER: A

The transmission of a given amount of power by a 3 phase system compared to single phase requires:

A) less conductor material

B) a different type of conductor material

C) the same amount of conductor material

D) more conductor material

ANSWER: A

Three phase distribution is more economical for the same power and voltage than single phase because:

A) less conductor material is required for transmission

B) the line voltage is greater than the phase voltage

C) the line current and phase current are equal

D) the line voltage is in phase with the line current

ANSWER: A

Single phase loads can be connected to a 3 phase distribution system that is:

A) 4 wire star connected.

B) 3 wire delta connected

C) 4 wire delta connected

D) 3 wire star connected

ANSWER: A

For a given wire size, a three phase system using 3 conductors can carry

A) 1.414 time the power of a two wire system

B) double the power of a two wire system

C) triple the power of a two wire system

D) 1.73 times the power of a two wire system

ANSWER: C

Last modified: Monday, 31 May 2021, 9:18 PM