Re: (ET) off topic but interesting...Field weakening

[Rod Hower <rodhower ameritech net>]

Back in my forklift design days at Caterpillar and
GE I was told that I shouldn't weaken the field more
than 30% (I'm sure there is lots of margin in that
figure).  This setup is poor man's field weakening
that does not automatically determine when it is
applied or when to drop it out (this is now the
operators responsibility).
Furthermore the cable shown in the picture probably
has an uncalibrated resistance, so actual field
weakening will vary on the same motor with each
device.
He also mentions 99.999% of golf carts etc, but quite
a few later model Club Cars use seperately excited
motors (although in the next sentence he somewhat
clarifies the previous by saying 'any series wound
motor').  While it may weaken the field on a wide
variety of series motors, it will do so with various
results.  For example, a 48V series wound has higher
field winding resistance, so this device will weaken
the field more proportionally.
This could also blow up the control under the right
conditions (like somebody engaging the contactor while
going up a hill).
Good luck,
Rod
--- "Chapin, Tim" <tchapin bf umich edu> wrote:
> 
> This auction is on eBay currently.
>
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=40155&item=714673
> 1105&rd=1&ssPageName=WDVW
> 
> It talks about increasing the speed of you series
> wound golf cart motor.
> It appears the kit is a solenoid some short cables,
> a switch to control
> the solenoid and some wire for the switch....
> 
> What is the guess on how this works?? Messing with
> the field on the
> motor? Skipping the controller and giving a straight
> hook from the
> batteries to the motor?
>  I have all the stuff pictured in the auction
> (didn't cost me close to
> the $75 the auction is) and have an old golf cart
> that is in need of
> more speed.
> 
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