Re: (ET) Alltrax output!

["David Roden" <etpost drmm net>]

On 23 Oct 2006 at 21:44, Ralph & Elaine Vogan wrote:

> The Alltrex does do field weakening (in forward only).

I was sure I recalled that it didn't.  So I went back through all my old 
emails from Steve Richardson.  In one of our exchanges, I reacted to 
something he'd said about the field map by saying that it didn't sound 
like 
the Alltrax did FW.  Steve didn't counter that remark.  But in fact at 
that 
point it was quite early in the development cycle and he didn't really 
know.

My apologies.  It turns out that I was wrong, and the Alltrax WILL perform 
FW to increase top speed.  However, as one person pointed out, the user 
has 
to explicitly turn that feature on; apparently, it's off by default.   

I haven't done this on my Alltrax, and my E15's top speed is definitely a 
bit slower than it was with the old GE control (which seldom bothers me).  
In fact, I'd entirely forgotten about the "Turbo" button in the control 
software.

FYI, here's some of what Steve wrote about how the Alltrax controls the 
E15 
field :

= = = = = 

Fri, 27 Jun 2003

The Alltrax controller automatically adjusts the field strength to keep it 
within a percentage of the armature current.  The armature current and the 
field current is monitored by the microprocessor and it decides, based on 
programmable variables, what the percentage should be.  

= = = = = 

Sat, 28 Jun 2003

As I understand the "Theory discussion" I had with Damon the controller 
will 
weaken the field with a light load and pedal-to-the-metal.  If the load 
increases then the controller will increase the field current to 
compensate. 
 This is really more to protect the armature than to control speed.  If 
the 
field is too weak with a given load then the armature current may rise to 
high.

= = = = = 

Wed, 7 Apr 2004

The Alltrax controller maintains a relationship between the field current 
and
the armature current that is in the motor's "sweet spot".  But we have
implemented a "Turbo" mode that can be turned on/off by the user.  It 
lowers
the field strength a little below normal when the throttle is full on and 
the
controller is not in current limit ( has a light load). 

= = = = = 

Hope this clears things up.


David Roden - Akron, Ohio, USA

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