Re: (ET) motor current

["Elie, Larry \(L.D.\)" <lelie ford com>]

That was poorly worded.  The voltage at the motor AFTER lead resistance
(droop) and the voltage drop at the batteries under load will be 36V or
less.

Larry Elie
 

-----Original Message-----
From: Michael S Briggs [mailto:msbriggs alberti unh edu] 
Sent: Thursday, July 27, 2006 4:23 PM
To: Elie, Larry (L.D.)
Cc: Neil Dennis; Elec-trak cosmos phy tufts edu
Subject: RE: (ET) motor current


The leads themselves won't have 36V dropped across them - by the lead 
voltage, I'm intending to measure the voltage drop from the PTO outlet
to 
where the wire lead connects to the motor, and use the voltage across
that 
wire, and its resistance, to calculate the current through the motor.

Mike

-- 

--------------------------------------------------------------
Michael S. Briggs
UNH Physics Department
(603) 862-2828
---------------------------------------------------------------

On Thu, 27 Jul 2006, Elie, Larry (L.D.) wrote:

> The motor is rated 3/4 hp at 36V.  Even on a full charge of 39+V, the
> droop due to leads will be about 36V.  That's the max power under
load,
> not the free spinning power rating.
>
> Larry Elie
>
>
> -----Original Message-----
> From: elec-trak-bounces cosmos phy tufts edu
> [mailto:elec-trak-bounces cosmos phy tufts edu] On Behalf Of Michael S
> Briggs
> Sent: Wednesday, July 26, 2006 6:02 PM
> To: Neil Dennis
> Cc: Elec-trak cosmos phy tufts edu
> Subject: Re: (ET) motor current
>
>
>
> On Wed, 26 Jul 2006, Neil Dennis wrote:
>
>> First, if you have an accurate voltmeter / ohmmeter, measure the
> voltage
>> drop along the power lead, check the resistance - that should give
you
> a
>> bllpark reading for the motor current.
>
> D'oh! Good idea, I should have thought of that - essentially use the
> lead
> for the motor as a shunt. *smack* (sound of me smacking myself in the
> forehead)
>
>> Do that before you try the 10
>> amp meter.  I'd guess that the motor draws more than 10 amps but
maybe
>> not.  Wonder, aren't they rated about 1 1/2 hp, that's about 1100
> watts
>> so go from there.
>
> Damn, that's 28 Amps, assuming 39 volts. They presumably don't always
> pull
> that much power, only when initialy starting up, and as needed to
> maintain
> speed while cutting. Still, that initial startup would likely just
blow
> the ammeter fuse. I'll use the lead as a shunt.
>
>> Have you taken the motor apart, maybe the field magnet is cracked,
> that
>> could cause the problem.
>
> Nope, haven't taken it apart. I figured I'd first see if I can find
some
>
> other problem causing it before disassembling the motor.
>       If that is the problem - do the large diameter and small
> diameter
> motors use the same field magnets? (I have a spare small motor, but
the
> three I'm using are large ones) If not, perhaps some place has
> replacement
> magnets?
>
> Thanks
> Mike
>
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