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How to calculate cable and cb/fuse sizes for motors

Farmboy
I haven't had to calculate cable and cb/fuse size(s) for single and 3 phase electric motors for some time now, but would like to do so as a matter of interest, so is there a contemporary reputable resource I can use that sets out how to do so (I could google/youtube it but don't know about their repute/accuracy)?


Thanks


F
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    OMS:




    Johnboy6083:

    A rule of Thumb is to size the cable for 1.4 x the running current. This allows for the increased volt drop during starting.




     

    and it gives you a useful "thermal reserve" in a cable subjected to multiple or frequent starting actions


    Regards


    OMS 

     




    And for the edification of most; oft ignored is the permissible starts per hour, see here for guidance. On a a pulp and paper mill during commissioning, they had problems matching the Kw rating of G.E.C. pump motors. With frequent starting, the windings on some were displayed at the ends until eventual failure. What was the condition of others, that were successfully commissioned? You're guaranteed till it expires! 


    Jaymack

    https://www.efficientplantmag.com/2015/05/safe-starting-of-motors-check-for-temperature-increase/

Reply
  • 0

    OMS:




    Johnboy6083:

    A rule of Thumb is to size the cable for 1.4 x the running current. This allows for the increased volt drop during starting.




     

    and it gives you a useful "thermal reserve" in a cable subjected to multiple or frequent starting actions


    Regards


    OMS 

     




    And for the edification of most; oft ignored is the permissible starts per hour, see here for guidance. On a a pulp and paper mill during commissioning, they had problems matching the Kw rating of G.E.C. pump motors. With frequent starting, the windings on some were displayed at the ends until eventual failure. What was the condition of others, that were successfully commissioned? You're guaranteed till it expires! 


    Jaymack

    https://www.efficientplantmag.com/2015/05/safe-starting-of-motors-check-for-temperature-increase/

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