RE: (ET) E20 main motor rating / max amperage

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

Some of the banter GE put out when the ET was introduced in Popular 
Science and Popular Mechanics 
said ALL the full frame tractors put out 20 hp with the difference being 
the duration.  Baloney.  
What is true is that the E20 was comparable to a 20 hp gas, etc.  How?  I 
have used a 20 HP Bolens.  
Running the deck probably takes 6 hp on that beast alone.  The ET deck is 
between 2 and 3 hp, but if 
you deduct the 6 hp off the Bolens, it only has 14 hp... no wait, it is a 
hydrostat... 75% drivetrain 
max, so 14 engine hp is only about 10 at the wheels... no wait again, a 
hydro works with poppet valves 
that are set for pulling not launch, so the ET launches better (your 300 
amps...) and why ET's win 
pulls.  In addition, the 20 hp Bollens probably never gets above 18 dyno 
even at the shaft because of 
other losses and atmospheric pressure changes and the fact that the max hp 
is at a specific torque and 
rpm combination.  The bottom line is the E20 is a good substitute for a 20 
hp gas, the E15/E12 likewise.  
But don't try to make the numbers work; The E20 motor won't do more than 8 
hp for even 2 seconds.  
>From your data....

Assuming 36V (which isn't true but is a starting point)

Power = V x Amps.

@ 50 Amps it's only 1800 watts.  760 watts (mechanical) is 1 hp.  The 
motor is pretty good, so 80% is OK for 2 hp.

@ 100 Amps we are only doing 3600 watts.  Around 4 hp.  The thermal 
breaker will trip in about 20 minutes at this 
level; I've done it disking.  The motor is less than 5 hp in reality.  But 
then there are the 3 .75-1 hp deck motors
too....  Nah, it still isn't 10 hp.

@ 400 Amps (brief launch) we are probably drawing 14 kW, but putting out 
11.  This would be 15 hp but it's only 
for 1/2 second or so.

So, it isn't as bad as Sears selling a 3 amp drill and calling it 3 hp, 
but it still isn't true.

Larry Elie





-----Original Message-----
From: elec-trak-bounces cosmos phy tufts edu
[mailto:elec-trak-bounces cosmos phy tufts edu]On Behalf Of Markus Lorch
Sent: Wednesday, July 28, 2004 10:45 PM
To: 'Markus Lorch'; 'SteveS'; 'et'
Subject: RE: (ET) E20 main motor rating / max amperage


> > I'm surpised at your current readings. My ammeter (150A max
> > hall effect 
> > probe)  usually runs around 30-40 A in flat mowing (traction 
> > motor and 
> > mower motors combined). I've never seen it run over 60 A or 
> so total. 
> 

Here the measurements I took this evening with my inductive Ammeter
attached to the wire going to the battery. The readings are fairly
rough numbers:

Driving on level asphalt road:
L, Speed 4    25 A
L, Speed 8    35 A
D1, Speed 4   35 A
D1, Speed 8   90 A
D2, Speed 4   50 A
D2, Speed 8   100 A

Mower motors with deck off ground, traction motor not engaged: 25A

Mowing on level ground :
L, Speed 4    50 A  (up to 75 A if there is an incline)
L, Speed 8    80 A  (up to 100 A  on an incline)
D1, Speed 4   75 A 
D1, Speed 8   120 A

This shows that mowing in L consumes a bit more power in Speed 8 than in 
D1,
Speed 4
BUT if one has to go slower then using the L speeds is much better.

Start on almost level asphalt road with max. accelleration:
L = briefly exceeding 400A, then quickly going down to 35A as the tractor
gets up to speed 
D1 = briefly exceeding 400A, then quickly going down to 90A as the tractor
gets up to speed
D2 = briefly exceeding 400A, then after a moment I can here the current
limitting turning of the field weakening, holding amperage for a second  at
300A, then decreasing to 100 A
as the tractor gets up to speed 


I hope you find these numbers interesting

Markus


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