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    pm_hardikar's Avatar
    pm_hardikar Posts: 2, Reputation: 1
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    #1

    Nov 6, 2009, 08:21 AM
    5 HP 3 P wire and CB sizing

    I have a 5 HP, 3 ph DOL started motor driving an air blower. The motor is situated at approx 50 mtrs from the nearest DB . Could you tell me the cable size and nos, type, rating, breaking capacity and the locations of MCBs in the motor circuit starting from the DB?

    <moved from Electrical Engineering and into it's own thread>
    tkrussell's Avatar
    tkrussell Posts: 9,659, Reputation: 725
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    #2

    Nov 6, 2009, 11:28 AM
    What does DOL stand for? Across the Line?

    Need to know voltage to detemine amp draw, to size the branch circuit size, overcurrent and overload size.

    What country are you located?

    What does this mean:

    and the locations of MCBs in the motor circuit starting from the DB?
    pm_hardikar's Avatar
    pm_hardikar Posts: 2, Reputation: 1
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    #3

    Nov 7, 2009, 02:06 AM

    DOL stands for Direct On Line( full voltage) starting.
    I belong to India. The voltage is 415 v, 3 ph,
    50Hz.
    Location of the MCB means starting from the distribution board up to the motor( distance 50 mtrs) how many MCBs I need to put in series and at which places? I want to totally eliminate fuses and Isolators.
    tkrussell's Avatar
    tkrussell Posts: 9,659, Reputation: 725
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    #4

    Nov 7, 2009, 05:07 AM
    You will need to check local codes or regulations to size the branch circuit and what type of cable, and the nameplate of the motor for actual amps but a 5 HP 415 VAC 3 Ph motor should draw about 7 amps.

    Local code will tell you the derating factor. Here in USA we take full load amps and increase by 25% to size branch circuit size.

    You are probably under IEE regulations, some help can be found here:

    http://www.tlc-direct.co.uk/Book/3.6.4.htm
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