RE: (ET) Alltrax regen brake / roll-detect feature

["Markus Lorch" <mlorch vt edu>]

Answering my own questions here: I just talked with an engineer from
Alltrax. Their controller constantly powers the field, but only with a
very small current. This way they can detect if the wheels start moving
and apply more power to stop it.

Their regen braking is really plug braking as I thought. They don't
put any power back into the batteries but rather short-circuit the
armature whilst powering the field to achieve the braking effect.

Markus

> -----Original Message-----
> From: elec-trak-bounces cosmos phy tufts edu 
> [mailto:elec-trak-bounces cosmos phy tufts edu] On Behalf Of 
> Markus Lorch
> Sent: Thursday, March 17, 2005 9:14 AM
> To: elec-trak cosmos phy tufts edu
> Subject: (ET) Alltrax regen brake / roll-detect feature
> 
> 
> Hi all,
> 
> I've read about these regen brake and roll-detect features of the
> alltrax and I have two questions:
> 
> 1. I thought the regen brake is more a plug brake. I.e. they shorten
> the armature with the field applied. I didn't have the impression that
> they actually increase the field strength to slow down the tractor.
> Or do they do that?
> 
> 2. When do they activate they field. It seems that for a brake and
> roll-detect
> function they have to have the field powered at all times. It 
> this the case?
> 
> I have bought myself also an alltrax, but for price reasons I 
> have chosen a
> model without the field control. My main motivation is to get 
> rid of the
> starting resistors in my E20 AA (for those of you who have seen how I
> mounted
> my front winch you know why :). The other reasons is that I 
> want to have
> more
> power in slow speeds, have a over-current limit (my FW 
> override circuit is
> bad),
> and I want to be able to gather power usage data via the 
> serial interface. 
> 
> Initially I will leave the 4 main F/R contactors and switch 
> direction this
> way.
> I will also leave the field weakening resistors in place. I 
> don't think I
> can 
> continue to power the field from the armature leads with  the 
> four diodes on
> 
> card 4 as the power signal on the armature will be pulsed and 
> would lead to 
> a reduced field strength. I am thus thinking of turning on 
> the motor field
> with 
> the key switch or whenever either the accellerator or brake 
> is depressed. 
> What do you guys think? How would you do it?
> 
> Markus
> 
> 
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