Cor,
How many turns did you wind? I'm assuming you removed the center
portion of the EI in order to get a rectangular shape?
Adam,
Check http://www.geepglobal.com/locations/usa/north-carolina/ if you
don't find anything high-power on craigslist.
I suppose if you need more room for wire you could get two and discard
the I sections as well as the center bars of the E sections and hold
them together with the openings facing each other...
On Mon, Aug 11, 2014 at 5:51 PM, Cor van de Water via EV
ev@lists.evdl.org wrote:
Adam,
I added a (free) inductor by wrapping the motor wires around the core of
the biggest microwave transformer that I could find.
You can pick up old microwaves most days from Craigslist and the like
for free. I occasionally get one, disassemble it if I can't get it to
work to give to a needy friend, so I have a stash of components to fix
the next one.
Note that it is required to put a very thin spacer between the two core
halves to avoid saturation and you need something (I used a very large
hose clamp plus 1 or 2 steel wires cross-wise along the core) to keep
the two halves together and aligned.
Cor van de Water
Chief Scientist
Proxim Wireless Corporation http://www.proxim.com
Email: cwa...@proxim.com Private: http://www.cvandewater.info
Skype: cor_van_de_water Tel: +1 408 383 7626
-Original Message-
From: EV [mailto:ev-boun...@lists.evdl.org] On Behalf Of Adam Chasen via
EV
Sent: Monday, August 11, 2014 2:16 PM
To: ev@lists.evdl.org
Subject: [EVDL] Protecting DC PWM Controller from low
inductance/resistancemotors
I recently purchased a 1980 Lectric Leopard (Renault 5 Le Car
http://www.evalbum.com/190) with the following specifications:
* original Presolite 6.7(?) series wound DC motor (presumably advanced
for
higher voltages)
* 16kWh LiPo NMC packs in 24s4p arrangement for 90V nominal with 150A
semiconductor on each of the 4 packs
* Curtis 1231C controller with PB-6
2 weeks ago I heard a loud pop as I depressed the throttle out of a
rolling
stop/turn and my voltmeter read 0. Seemed like my semiconductor fuses
did
the job and all 4 were popped ($100 worth of fuses mind you).
Unfortunately in my distressed mindset I bypassed the fuse on one pack
and
the car lurched a few inches as soon as I flipped my breaker and then
stopped (I know, bad call).
I disassembled the Curtis controller and discovered 2 gently blown
mosfets and 1 catastrophic mosfet failure. I ordered replacement
mosfets
IXTH50N20. One trace on the power board looks like it overheated and
there
appears to be some damage (a resistor?) on the control board. There is
possibly damage to a trace in an internal layer, but not sure if it is a
2
layer board and some surface heating caused some damage.
I have since swapped the Curtis out for a 750A Logisystems which I am
aware
are plagued with (similar?) issues. These failures appear to be due to
low
resistance/low inductance motors causing a overcurrent condition. The
logisystems doesn't provide for a 1.5kHz during startup. That is a bit
concerning as that was the workaround for the Curtis.
I have since measured the motor side of the controller with an inrush
current sensor and measured 645A max even with being very careful to
slowly
depress the throttle.
My concern centers around this happening again, especially on my larger
1989 BWM 535i with a directly coupled FB1-4001a motor. There are a few
proposed solutions I read about and a few I came up with on my own which
I
am soliciting opinions on.
A big unknown to me is how much resistance or inductance needs to be
introduced to prevent this kind of inrush/runaway.
One solution is to use the clutch in the Leopard to ensure there is no
starting load on the motor. I still measured inrushes of 300A with no
load! That will not work for my directly coupled 1989 BMW. I am curious
if
Lee Hart (with his Leopard) and others with series wound DC motors drive
using the clutch. I have since modified my shifting behavior to much
higher
RPMs after reading some about his driving style.
Another is to control the current with a large inductor. There was a lot
of
talk, but no pictures of these inductors. I am not sure how much
inductance
is necessary to help, but haven't done much research into this. There
was
some mention of using surplus transformers with insulated layers, but
wasn't able to get a good picture in my head of size and process.
Someone
mentioned a 30 lbs choke on an older PMC, but that also doesn't provide
me
a good picture in my head other than it will likely be bigger than any
non-power system transformer I have ever seen. Where can I get one (or
the
materials for) of these inductors and how much will the cost?
There are two other passive electronic components which can control
current
I didn't see mentioned.
* Resistors
* Thermistor
I am not sure about the practicality of using a thermistor for this
purpose
