Page 292 - Electrician - TT (Volume 2)

ELECTRICIAN - CITS

9 The length of flexible conduit should not exceed 1.25m.

10 The minimum cross sectional area of a conductor used in power wiring should not be less than 1.25mm2in the
case of copper and 1.5mm2 in the case of Aluminium conductor.
11 Earth wire should be of copper or galvanized iron. The cross sectional area of copper earth wire should be
greater than half of that of the largest rated current carrying conductor.
12 The fuse should be capable of carrying the starting current of the motor(normally two times).
13 Every main switch board should comply with the following provisions,
a A clear space of not less than 1mtr. In width should be provided in front of the switch board.

b If there are any attachments or bare connections at the back of a switch board, the space behind it should
be either less than 22.5cm or more than 75cm in width, measured from the farthest protecting part of any
attachment or conductor.

c If the space behind the switch board exceeds 75cm in width, there should be a passage way from either
end of the switch board, clear to a height of 2mtr.
13 In the manufacturing industry, the maximum load connected to a 3phase, low tension supply of 415V to
100kVA.
14 If the load exceeds 100kVA and is below 1000kVA, a 11kV supply to be given to the consumer.
15 To get an EHT supply, the connected load should be more than 3000kVA.
16 Motors up to 150hp of low tension supply, 3ph.

17 Motor capacity above 150HV, HT supply 3.3kV, 6.6kV or 11kV rating.

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CITS : Power - Electrician & Wireman - Lesson 104&105