RE: Rudman Was Right! (was Dualin'7s Smoked Controllers)

["Roger Stockton" <rstockton@delta-q.com>]

Hi Rich,

Sorry about wearing you down, I expect typing may still be a bit
unpleasant for your hands... but thank you very much for sharing
all this real-world info!

You note that the controllers can only provide 1200A for a very
brief time, but I have attached a post from Damon stating that
brief time as being almost enough to get you down the 1/4!
Certainly long enough that you'd expect the motors to be limiting
the current below 1200A well before the controller thermal cutback
needed to...

Cheers,

Curious George  ;^>

-----Original Message-----
From:	Damon Crockett [SMTP:fetsmoke@az.com]
Sent:	Friday, February 12, 1999 4:17 PM
To:	ev@listproc.sjsu.edu
Subject:	Raptor/T-Rex Design notes

[snip]

The MOSFETs in a Raptor 1200 will do the following:
Pass 1200A through to the motor for ~10 seconds @ 100% duty cycle (full
on)
before the unit begins limiting current due to transistor heating.  This
is
an idealistic condition where the motor will just pull 1200A from the
battery pack.

At 50% duty cycle, the MOSFETs can pass 2400A pulses, for an average
current of 1200A.  The peak desaturation current limit increases as the
duty cycle decreases to about 3:1 max, i.e; about 3600A peak pulse
current
allowed at 33% duty cycle.  You still have 1200A average battery
current. 
By the way, the internal filter capacitors of the controller supply this
3600A pulse current, not your batteries.  At the same time, the Motor
Current COULD concievably reach 3600A, but it won't.  The motor has
resistance losses, and the afformentioned eyeball/tire smoke condition
will
occur.