Re: (ET) Alltrax install!

[Robert Adsett <subscriptions aeolusdevelopment com>]

Quoting "David Roden (Akron OH USA)" <etpost drmm net>:
> I may be wrong, but my understanding of plug braking is that it does not
> actually apply reverse current.  Rather it maintains the field current 
> while
> short-circuiting (or nearly so) the armature.  This stops the motor very
> quickly.  If I'm wrong about that, I certainly welcome correction of my
> misapprehension from the designers of the Alltrax, the designers of any 
> other
> plug-braking controller such as a Curtis, or those who have studied plug-
> braking controller design.

I would call that regen not plugging.  To plug you reverse the motor (and 
I am
one of those who design controllers).  I did a lot of work on plug braking 
for
series wound motors but we only deliberately plugged PM and SEM when 
the torque
had fallen too low to achieve sufficient braking with regen, and by that 
point
there was usually no net feed back to the battery in any case.

I wouldn't object to someone using another term than regen (resistive 
braking
comes to mind) since the motor is regenerating into the controller rather 
than
the battery but it is certainly not plugging.

I do see the difference between plug and regen as being more than where 
you put
the current generated by the motor.  This is, however, an industry where 
terms
have generated there own meanings in various sub-cultures.  You can see 
why I
would be surprised that anyone would mention plugging as a primary 
braking mode
of a separately excited controller though :)

> My 115 volt push mower uses plug braking, not a mechanical brake.  It's a
> PM motor, and when the mains switch is opened, it closes the contacts
> across the motor armature leads.  The motor stops very quickly, I would say
> within a half-second or so.  This is exactly the same method GE used to
> stop the PM mower motors on the deck.

Again that's not plugging.  Plugging would stop it even faster, of course 
you
might blow something in the process ;)

> > I am sorry if I offended anyone, that is not what I am trying to do here.
>
> I don't know about anybody else, but I'm not at all offended.  You don't 
> need
> to SHOUT, though.  ;-)

No offense here, I hope I haven't been shouting.  I don't think I was 
:).  It is
important though that we all understand what we mean by the terms.  If the
Alltrax was really using plugging I'd be worried about it.

Robert