From: Joe Foley (redmenaced@yahoo.com)
Date: Tue Oct 21 2003 - 15:22:02 PDT
Eyup!
I'll vouch for all of this, you really can't tell how
much it will draw unless you see the manufacturer's
info, starting current will be anybody's guess.
Joe
--- noel shelley <noel@shelley1722.freeserve.co.uk>
wrote:
> Dear All ,
> There are several ways to configure
> the starting of an
> induction motor , each method has plus and minus
> points . Capacitor start
> ,induction run will give a very high starting torque
> but draw upto 550% of
> its full load current . Split phase starting can
> draw upto 1100 % {yes thats
> right 1100 % } of full load .
> Ordinary simple fuses are unsuitable , because if
> they stand the start they
> are to big to protect the motor ,the use of thermal
> cutouts of the correct
> rating and proper setting are the best method
> normally with a contactor .
> You NEED to know the full load current , the H.P. or
> Wattage is not good
> enough . 746 W = 1 H.P. is a 100% efficiency
> conversion & never attained in
> practice E.G. 3hp = 2.2 Kw = 18.3 A@ 120V WRONG ,
> more likely to be about
> 32A in practice dependant on the type of motor.
> I had a small compressor 1/4 H.P. 180 W that could
> not be started by a 2KvA
> generator {split phase start } yet would run a 750 W
> drill with ease. I also
> use a 3H.P. 2.2 Kw motor that starts light , on 240V
> full load is 17.6 A
> starting
> current is in excess of 60A.
>
> HOPE this may be of help Noel
>
>
>
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