Sorry to reply to my own post but "motor current when voltage changes"
thread
has cleared things up a bit. Thanks

> -----Original Message-----
> From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu]On Behalf
> Of peteHVAC
> Sent: Monday, November 13, 2006 7:07 PM
> To: Microcontroller discussion list - Public.
> Subject: [ee] Best way to control a large dc motor
>
>
> Yup, that was quite the brain fart sorry about that. Since nobody knows
> me here I'll risk further imbarrasment. It would be V/R wouldn't it?
> I calculated 120 amps from a measurement of .3ohms and 36 volts. When
> I locked the rotor and applied voltage, from a good distance away, I
> measured 643 amps. The armature and feild are connected in series.
> It was very exciting to actually measure the current but I don't think
> I'll ever do that again.
> How can I make a quick estimate of lock rotor amps for a series motor?
>
> > -----Original Message-----
> > From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu]On Behalf
> > Of Olin Lathrop
> > Sent: Monday, November 13, 2006 8:20 AM
> > To: Microcontroller discussion list - Public.
> > Subject: Re: [ee] Best way to control a large dc motor
> >
> >
> > > peteHVAC wrote:
> > >> I heard tell that measuring resistance of the motor and
> multiplying by
> > >> voltage would give a close value of the lock rotor amps. any
> > >> truth in this?
> >
> > Martin K wrote:
> > > Yes that is true.
> >
> > Huh!!?  The units don't even match.  Ohms times volts comes out
> > to Kg m**2 /
> > S C**2.  I can't think of how such a quantity is meaningful, but it
> > certainly isn't C / S.
> >
> >
> > ********************************************************************
> > Embed Inc, Littleton Massachusetts, http://www.embedinc.com/products
> > (978) 742-9014.  Gold level PIC consultants since 2000.
> > --
> > http://www.piclist.com PIC/SX FAQ & list archive
> > View/change your membership options at
> > http://mailman.mit.edu/mailman/listinfo/piclist
> --
> http://www.piclist.com PIC/SX FAQ & list archive
> View/change your membership options at
> http://mailman.mit.edu/mailman/listinfo/piclist

-- 
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist