20)Step 1

a) Step 1

Collect the system data for which busbar system has to be design


VOLTAGE RATING 415V, 50Hz. 3Ph. - 3Wire

CURRENT RATING 2000Amp.

WELL VENTILATED ROOM

MAX. FAULT CURRENT 50 KA

LENGTH OF BUSBAR = 500mm

AVERAGE AMBIENT TEMP. = 50 deg. Centigrade


Calculate the derating factors for ambient temperature, enclosure, proximity effect.

1) Derating factor for Ambient Temperature



Df1=0.81

Actual average ambient temp. = 50 deg. C
Manufacturer average ambient temp. = 35 deg. C
Final ambient temp. = 85 deg. C


2) Derating factor for enclosure & ventilation


From table we can see that for well ventilated room, where cross-sectional area of busbar is 10% of total cross-sectional area of enclosure derating factor is

Df2=0.65

3) Derating factor for Proximity effect

For 3W phase spacing derating factor for proximity effect is

Df3=0.82

Calculate effective derating factor.

Df = 0.81 * 0.65 * 0.82

= 0.43




Select the busbar size

Minimum rating of busbar required

= 2000/0.43

= 4651 amp.

Busbar selected = 203.2 * 9.53 mm (3 flats)