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Re: (ET) Thinking out loud - Controller

Some have noted that they can't see the utility of infinitely variable 
speed.  Maybe I'm the only one who gently nudges round obstacles and backs 
the ET into the garage right up to a project car's bumper, but after using 
an Alltrax for some years now, I would NEVER go back to the jumpy GE 
controller.  Yea, verily, even though it costs more to do it this way.

As for the cheap choices, it's worth noting that a Curtis series motor 
controller isn't designed for sep-ex use.  Curtis depends on having a 
certain amount of motor inductance for its current limit to respond fast 
enough, and I don't think the ET sep-ex motor provides enough.  This means 
that in an ET a Curtis series motor controller might not be able to 
properly 
limit peak currents.

For that reason I'd recommend that you choose a Curtis with a current 
capacity well above the highest peak you expect the ET motor to draw, to 
improve your chances of keeping the magic smoke in the controller.

I would also urge caution with the Curtis sep-ex controllers someone 
pointed 
out on Ebay.  Sep-ex motors need proper field current management and the 
controller should be matched to the motor.  You can end up damaging your 
motor with the wrong field map.  

If you have a Curtis programmer, you might be able to tweak these to suit. 
 
But I don't know that for sure; they might be set in firmware for a 
specific 
manufacturer's motor.  And Curtis programmers are EXPENSIVE unless you can 
borrow one.  

I suppose you might be able to just forgo the field output and power the 
field with full battery, but then you lose top speed as mentioned 
elsewhere. 
 
In any case adapting either one of these controllers to an ET may not be a 
trivial task, and I don't think I'd recommend it for someone who doesn't 
have at least a bit of motor and electrical background.

The orthodox choice is an Alltrax ET controller.  

http://electrictractorstore.com/index.php?main_page=product_info&cPath=3_24_2
9&products_id=41

or (for now) http://tinyurl.com/495224u

This is a bolt-in modification, but it does require that you understand 
how 
to read schematic diagrams, and you have to follow the instructions very 
carefully.  I fitted one to my E15 some years back and had no trouble at 
all, but IIRC one or two others managed to somehow damage one or two 
controllers before getting everything right.  You might find something 
about 
that in the list archive.

Alas, the Alltrax price has gone up substantially since I bought mine.  In 
2004 the 300 amp version (which seems to be the only one now on offer) was 
$215, and my 400 amp controller was $289.  Now the 300 amp version is $400.

For a bit more cost, risk, and effort, but some advantage, you might 
consider a 4QD controller.  They're intended for PM motors, but many of 
them 
have (or can be supplied with) brake release outputs that can be used to 
operate a field relay.

http://www.4qd.co.uk/

I see that thanks to the weak dollar a 4QD-300 (240 amps) has gotten 
pricey 
too, UKP304.50 plus P&P (US$490).  Despite the price, if I had to replace 
my 
Alltrax today, I'd consider this controller for its reportedly excellent 
speed regulation.  The only thing I don't like about the Alltrax is that 
it 
allows the tractor to speed up more going down hills than the original GE 
system did.  

If you can live with a lower current limit (I don't know how low you could 
go on a large frame ET without losing significant torque), a 4QD-200 (180 
amps) is cheaper at UKP241.50 (US$389).  

The 140 amp 4QD Pro-150 is more affordable still at UKP181.65 plus 
(US$292). 
This controller also comes with a programmer and battery level display 
board.  It doesn't seem to have a brake output, though, so you'd have to 
devise some other way to make sure the field was powered up before you 
applied voltage to the armature.

If interested in the 4QD controllers you may want to contact a US 
distributor.

http://www.4qd.co.uk/addrs/distr.html#USA


David Roden - Akron, Ohio, USA

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