Three Phase Distribution

Question 1

What voltage is derived from a substation transformer?

Answer 1

400/230 volt

Question 2

What method is used in the secondary winding

Of the substation transformer ?

Answer 2

Star point

Question 3

What is phase voltage?

Answer 3

Phase voltage is the voltage (230V) between any live line (L1,L2,&L3) and the neutral.(single phase )

Question 4

What is line voltage (UL)

Answer 4

The voltage between two live feeds (L1&L2, L1&L3, L2&L3) it is 400volts (three phase)

Question 5

What are the wire colour codes for three phase systems ?

Answer 5

Brown =L1
Black =L2
Grey=L3
Blue =Neutral
Green/yellow= Earth

Question 6

What is 3 phase 400 volt 4wire supply used for ?

Answer 6

Unbalanced three phase loads as they require a neutral.

Question 7

What is a 3 phase 400 volt 3 wire supply used for?

Answer 7

It is used for balanced loads such as three phase motors which do not require a neutral.

Question 8

What is 2 phase 400 volt 2 wire supply used for

Answer 8

Used for loads such as welders

Referred to as 1 phase 400 volt supply

Question 9

What is 1 phase 230 volt supply used for ?

Answer 9

Used for loads such as lamps, heaters & computers.

Question 10

Name the three different neutral bars that can be found in a three phase board ?

Answer 10

1. Main neutral bar
2. Single phase neutral bar
3. Three phase neutral bar

Question 11

What is ran into a three phase neutral bar?

Answer 11

Three phase sockets neutral

Question 12

What should a three phase socket circuit be protected with ?

Answer 12

Three phase RCD

Question 13

What does HBC in HBC fuses stand for ?

Answer 13

High Breaking Fuses.

Question 14

What is another name for a high Breaking fuses (HBC)?

Answer 14

High Rupturing Fuses

Question 15

How quick can a higher breaking fuses (HBC) break a short circuit ?

Answer 15

0.01 sec

Question 16

What is the disadvantage of a high Breaking fuses ?

Answer 16

Expensive

Question 17

What are the advantages of hight breaking fuses (HBC) ?

Answer 17

Can distiguses between over load current for motor start up and high fault current

No fire risk

Will not deteriorated with time

Capable of breaking very high value fault currents

Question 18

What is the fusing factor if high Breaking fuses ?

Answer 18

1.25

Question 19

What is a type C MCB ?

Answer 19

A type C MCB is used in industrial wiring.

Question 20

What is the difference between a type b and type c MCB ?

Answer 20

Type C can detect a over current for the start of a motor and not trip but can also detect short circuits in the case of a fault

Question 21

What is the magnetic tripping facto of a type C MCB ?

Answer 21

5-10 time it’s rated current

Question 22

What is the thermal tripping factor of a type C MCB?

Answer 22

Between 1.13 & 1.45 the same as a type B MCB

Question 23

What colour is a 110 volt plug and socket?

Answer 23

Yellow

Question 24

What colour is a 230 volt socket and plug ?

Answer 24

Blue.

Question 25

What colour is a 400 volt plug and socket?

Answer 25

Red

Question 26

At what position of a clock is the earth sleeve located on a 110 volt plug ?

Answer 26

4 o’clock position

Question 27

What position is the earth sleeve on both 230 volt and 400 volt plugs ?

Answer 27

6 o’clock

Question 28

What is the CENELEC plug and socket standard for industrial uses ?

Answer 28

EN 60309