Re: ?over voltage battery pack?

[Eric Jelinski <jelinski@idirect.com>]

At 09:57 PM 30/08/98 -0700, somebody wrote:
>OK, now it's time for someone to design a clever little circuit that
>clamps the effective throttle pot resistance when the average voltage @
>the motor reaches a predetermined value. I coulda used something like
>that with my XP-1263 / Grizzly / 180V pack...


I run my Citicar motor that has a name plate voltage of 36 volts.... I run
it at a nominal pack voltage of 72 volts .... which is up to 85 volts with
a surface charge.  I've been doing this for about 5 years now.   Way I
figure I'm able to do this without destroying the motor is based on two
reasons:
1)  The motor electrical insulation voltage break down rating is way higher
than the nameplate.... we don't know how high, but for a 36 volt nameplate,
it ought to be, my guess, atleast several hundred volts before insulation
that is in good condition will break down.... note this caveat (good
condition).   2) A magnetic permeability test on the motor will determine
when the motor magnetically saturates, ie. the point at which an increase
in voltage no longer results in a increase in magneto-magnetic force (mmf),
ie no more real shaft power output; instead the motor heats up.   I did
this test for one of my Citicar motors and it turns out that it staturated
at about 60 volts.   Given that the typical controller being a PWMC eg.
Curtis,  it is the "average" voltage that is of concern when in saturation.
 And, since this state of "high average voltage" occurs only for short
periods of time (acceleration), monitoring the motor temperature would be
more indicative of the state of the stress imposed on the motor.  If this
does not make sense.... comments please.

Eric Jelinski
Durham Electric Wheels
# 2 Waverley Road
Bowmanville, Ontario, Canada, L1C 1k7
phone  905-623-6653   fax 905-697-1414
e-mail  jelinski@idirect.com
web    http://www.durhammall.com/electricwheels
Electric Vehicle Products and Services