Re: (ET) Curtis or any generic controller setup - Finally.

["David Roden" <etpost drmm net>]

On 2 Aug 2012 at 3:26, Robert Troll wrote:

> They key is two micro
> relays...
> 
> http://www.youtube.com/watch?v=OxGJax5Q7Ng&feature=youtu.be
> 

The video clip is fine as far as it goes, but it left me puzzled.  It does 
show that the motor reverses, but it doesn't explain what the relays are 
for 
or how they're connected.  (Maybe that'll be in next week's episode. ;-)

I'm assuming this is a standard series golf-car motor controller.  I've 
never tried one with an ET motor, but I know others have.  A couple of 
them 
have posted here in past years.  

It should work, if you provide some means of ensuring that the field is 
powered before you apply voltage to the armature.  I suppose you could do 
that with a relay, enabling the Curtis's KSI only if field voltage is 
present.  Even better would be a reed relay that sensed field current 
instead - that would prevent enabling the controller if a relay connection 
broke or fell off.

One gotcha remains, however.  Without a full field in series with the 
load, 
the ET motor may not have enough inductance to make that Curtis happy.  
Its 
current limit may not be able to react fast enough to protect it from 
overcurrent.  The symptom of this in road EVs is rough, lurching starts 
when 
pulling away from a stop.  

This is the best (and by far the most entertaining!) explanation I've read 
of how this happens :

http://www.evdl.org/pages/hartcontroller.html

If the controller is sufficiently oversized, it might survive just fine, 
at 
least under normal operating conditions, but there's still some risk.  


David Roden - Akron, Ohio, USA

= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = 
Note: mail sent to the "etpost" address will not reach me.  To send 
me a private message, please use the address shown at the bottom
of this page : http://www.evdl.org/help/
= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =