EV Digest 6814
Topics covered in this issue include:
1) Blowing up IGBT's (was Triangle wave generator)
by "Dale Ulan" <[EMAIL PROTECTED]>
2) Treadmill motor torque speed curves
by Rod Hower <[EMAIL PROTECTED]>
3) RE: Award winner!!
by "Alan Brinkman" <[EMAIL PROTECTED]>
4) RE: How regen works
by "Dale Ulan" <[EMAIL PROTECTED]>
5) Re: Burnt out PM Motor?
by Jeff Major <[EMAIL PROTECTED]>
6) Re: Triangle wave generator
by Lee Hart <[EMAIL PROTECTED]>
7) Re: Triangle wave generator
by Lee Hart <[EMAIL PROTECTED]>
8) Re: Split pack DC/DC balancing
by Lee Hart <[EMAIL PROTECTED]>
9) Re: AGNS misses 168 record
by "Rich Rudman" <[EMAIL PROTECTED]>
10) RE: Fast and Eff!!! Re: White Zombie gets to 'test' drive Lithium!
by MIKE WILLMON <[EMAIL PROTECTED]>
11) RE: Main Contactor Ebay Search Criteria
by "England Nathan-r25543" <[EMAIL PROTECTED]>
12) Re: Lancia Scorpion EV site finally up
by "Peter Gabrielsson" <[EMAIL PROTECTED]>
13) RE: Electric motor for air conditioning or power steering
by [EMAIL PROTECTED]
14) Re: Electric motor for air conditioning or power steering
by electro <[EMAIL PROTECTED]>
15) RE: Electric motor for air conditioning or power steering
by Mark Ward <[EMAIL PROTECTED]>
16) Re: Electric motor for air conditioning or power steering
by "Evan Tuer" <[EMAIL PROTECTED]>
17) www.DriveCongress.com
by Marvin Campbell <[EMAIL PROTECTED]>
18) Re: Electric motor for air conditioning or power steering
by "Roland Wiench" <[EMAIL PROTECTED]>
19) RE: Main Contactor Ebay Search Criteria
by Lee Hart <[EMAIL PROTECTED]>
20) RE: Electric motor for air conditioning or power steering
by Mark Ward <[EMAIL PROTECTED]>
21) Re: Electric motor for air conditioning or power steering
by Danny Miller <[EMAIL PROTECTED]>
22) Re: How regen works
by "(-Phil-)" <[EMAIL PROTECTED]>
23) Re: How regen works
by Danny Miller <[EMAIL PROTECTED]>
--- Begin Message ---
>OK I think I understand... so when you did follow the application notes
>to the letter everything worked?
Well, it has so far, but other than a quick dyno-test on my
motors, I don't have a lot of miles on them to make sure.
They looked good on-the-bench, though. I've been concentrating on
motor electronics lately, getting a set of BLDC's running
for this summer's (or maybe next winter's) project car.
>But even though you have followed the application notes your should
>still look for spikes or other problems at low voltage?
Yes, because of interactions between the gate drivers, control
circuitry, etc. But if you follow the app notes very carefully,
you minimize the chances of things going wrong, so hopefully
you don't find anything wrong when you look for them. But if
you don't go looking for anything, and you miss something, then
it blows up. I've done that enough times to have learned.
Even in the low-power world, you still have these problems.
You also learn from other people's mistakes. The original
Solectria BLDC controllers are a mess. Every one of them
that I've met has been repaired numerous times. Even a well-known
audio power amp manufacturer (Crown) has a known issue with
its DC300A power amp. It happens. You try to minimize it as
a designer, though.
>So youre saying that ...even if you have followed the physical aspects
>of he application notes to the letter the IGBT could still blow up , or
>be inefficient and overheat if your controller doesn't switch them
>correctly?
Yes, absolutely. This is less of a problem with the intelligent
IGBT modules, such as those sold by Powerex, as they have matched
the switching speeds of the IGBT's to the recovery characteristics
of the diode. So long as you use the correct snubbing network with
the correct types of parts, it should be ok - but check, anyways.
If you are using bare IGBT's, or MOSFET's, then you can definitely
cook the parts by driving them incorrectly. Too fast of a switching
speed results in stressing the freewheeling diode. Too slow of a
switching speed may result in excessive heat buildup. Too much
coupling on the gate drive lead - or a lot of parallel devices
without enough gate lead oscillation stoppers - may cause the device
to oscillate at a very high frequency during the turn-on or turn-off
periods. That'll blow something up eventually - or immediately.
As for those fast spikes, the solution isn't necessarily a faster
scope, though you'll see them better. Remember that the 'scope
bandwidth only attenuates the spike - kind of like the treble
knob on your stereo can attenuate the high frequencies.
But you can see that it's there - the amplitude is just displayed
wrong. Look for oscillation due to gate drive problems or parallel
device oscillation, look for wrong switching speeds. One of these
sorts of things will cause that little spike and when you correct
the source of it, the blip or fuzz on the 'scope will go away.
Remember, the scope isn't lying to you, but it doesn't always tell
you the whole truth either. If you have a 60-100 MHz scope then you
can probably work with it. A 10 MHz scope isn't very useful, though.
It is just too slow to be working with these sorts of devices at
these sorts of switching speeds. Even in my audio design work (yes,
I design a bit of everything!) I like to have a reasonably fast
'scope to check for oscillation. Audio op-amps such as the LM833
and NE5532 like to oscillate at around 6 MHz.
-Dale
--- End Message ---
--- Begin Message ---
For those interested, I posted a PDF of two treadmill
motors at the site below.
I also sent a copy to David Roden to post at
http://www.evdl.org/lib/index.html
http://autos.groups.yahoo.com/group/tevan/files/
--- End Message ---
--- Begin Message ---
John,
I was looking at your HD Servi-Car in the EV Album last week and was
impressed with your quality work. How did you get the belt pulley to
mount up to the motor? Is that a stock Harley Davidson pulley on a
splined shaft motor?
I am collecting parts for a two wheeled HD type project and am thinking
to move to a series wound motor. The permanent magnet motor I have will
likely not supply the torque needed at slow speeds, and the gear
reduction is hard to work out.
Your hard work has paid off in a very nice looking machine!
Alan
-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On
Behalf Of [EMAIL PROTECTED]
Sent: Thursday, May 24, 2007 7:45 PM
To: ev@listproc.sjsu.edu
Subject: Award winner!!
Hi all,
The Skunk is now officially an award winning conversion. I was in a
parade
last Saturday and was awarded 1st place in the motorcycle division. I
just
received the plaque today so its official. Just a small town parade,
but
lots of viewers and many comments and discussions afterwards with the
spectators. There was a car show in conjunction with the parade and I
was
parked with them afterwards where I got the comments.
Also I'm almost up to 500 mi on the bike as an electric.
respectfully,
John
The Skunk, 58 Harley servicar conversion.
http://www.austinev.org/evalbum/751
--- End Message ---
--- Begin Message ---
As I understand it (and it's been a couple years since I played with
them), for an NPN Mosfet to conductm the gate has to be approx 10V more
positive than the drain (unless you are using one of those 'spensive
FETs).
It needs to be 10V more positive than the source, not the drain.
But in any case, when running the MOSFET in reverse, the diode is
conducting. Let's use the bottom-side MOSFET. So the source is
at 0V, and the drain is at -0.7 volts (the motor's inductance plus
the diode drop creates this). The MOSFET will happily conduct in
reverse if the drain is within a volt either way of the source,
when you turn it on. So when you apply 10V (gate to source)
the FET turns on, and the voltage on the drain of the FET drops
to - (Iwinding * Rdson). For, say, a 50 amp current and a .005
ohm Rdson, you'll get -0.25 volts on the drain of the FET relative
to the source.
The key to synchronous rectification is that the MOSFET diode would
have been on anyways, creating a -0.7 volt drop (or thereabouts).
Turning on the MOSFET just lowers that drop providing that Rdson
is low enough.
In ICE engine controllers, it is common to use a P-channel FET in
reverse for reverse polarity protection to prevent the engine
management computer from blowing up in the case of a reverse voltage.
How that works is identical to synchronous rectification.
-Dale
--- End Message ---
--- Begin Message ---
Just so happens my friend has his motor in here today.
I think it is the same as Marks. He fried his NiCad
pack last week. So he outfitted it with 18 volts of
PbAcid. Just ran a nolaod test (without blade). 2608
RPM at 18.4 volts. So 142 RPM/Volt.
So another way to check for demag, if you have a
strobe or tach, remove blade and run no load motor
test. If RPM per volt is higher, demag!
As long as we have it the lab, took a no load current.
9 amps. Seems a bit high. Aaron went home to get
the blade and brought in his spare motor. New, never
run. Put it on the power supply, 18.6 volts, 2360 RPM
at 4.5 amps, no load.
Both were at room temp. The used one, higher RPM and
9A, has cut about 10 or 12 times. Never overheated to
his knowledge. Has a small yard and small battery.
Is it possible these motors just degrade with use?
One wouldn't think so. Unless the starting current
pulse is enough to demag. He just put an analog
ammeter on it and started it with the blade, 18 volts,
hit a peak of 100 amps. Running at 28 amps on
concrete floor. He says it used to draw 22 amps
cutting thin grass.
Another motor puzzle. Two in one week.
Jeff
--- Jeff Major <[EMAIL PROTECTED]> wrote:
>
> Rod, Mark,
>
> To test for demagnetization, you could run a
> generated
> voltage test, couldn't you? Drive the motor at a
> set
> speed and measure terminal voltage. Then proportion
> up to nameplate (or original no-load rpm) and if the
> voltage is a lot less than 24, opps, demagged. Then
> what? Could you remag by turning brushes 45 degrees
> and pulsing with a couple hundred amps?
>
> Sticky brush is also possible problem.
>
> Jeff
>
>
>
> --- Rod Hower <[EMAIL PROTECTED]> wrote:
>
> > If the motor was REALLY hot on 24Vdc there's a
> good
> > chance you demagnetized the PM field or at least
> > weakened it to the point of having much less
> > performance. If this is the case, I would think
> it
> > still gets pretty warm at 18Vdc. Also make sure
> > that
> > the brushes are properly seated on the commutator
> > and
> > not sticking in the holder.
> >
> > Rod
> > --- Mark Hastings <[EMAIL PROTECTED]> wrote:
> >
> > > I have a 4 brush 24 volt 1.5 PM motor on my 22"
> > > mower.
> > > I had run it initially on 24 volts but it got
> far
> > > too
> > > hot. I now run it at 18 volts and it worked for
> a
> > > couple mows.
> > > However now it just has no power at all. Any
> tall
> > > grass and it bogs down incredibly like the
> > batteries
> > > are dead. I even tried putting it back to 24
> volts
> > > and
> > > get the same results. Does this sound like I
> > ruined
> > > the motor in my initial runs at 24 volts? It is
> > > almost
> > > as if the batteries are dead. They are freshly
> > > charged
> > > batteries along with a brand new set of freshly
> > > charged batteries I just purchased.
> > > It had been cutting wonderfully but now I can
> > > hardly
> > > use it.
> > >
> > >
> >
> >
>
>
>
>
>
____________________________________________________________________________________Pinpoint
> customers who are looking for what you sell.
> http://searchmarketing.yahoo.com/
>
>
____________________________________________________________________________________
Park yourself in front of a world of choices in alternative vehicles. Visit the
Yahoo! Auto Green Center.
http://autos.yahoo.com/green_center/
--- End Message ---
--- Begin Message ---
tt2tjw wrote:
Are you saying
1. Your first attempt did not follow the application notes and resulted
in blown parts then a subsequent attempt followed the application
notes and was successful?
or
2. Your followed the application notes and still blew up parts; then
tested with an oscilloscope and tweaked the design so that it worked?
This may be a stupid question - I am a proto novice..... What do you
mean by "tame the parasitics"? Do you mean that the switching of the
IGBT causes noise in the control signal?
The problem is that manufacturer's application notes are only a rough
sketch of what needs to be done. They are often written in a hurry, and
either not tested at all, or only tested very briefly. They leave out
many important details, like bypass capacitors, snubbers, fuses, wiring
practices, heatsinking requirments, etc. A skilled engineer is expected
to know these things and add them -- but a novice is likely NOT to do
so. The result will be a circuit that works badly, or not at all.
Manufacturers sometimes get around this problem by offering a pre-built
PC board that has the complete, tested circuit. These are much better
(at least you know someone actually built one). But they still tend to
be rather oversimplified; they are being built for experts, after all.
If you look at a real circuit, in a real mass-produced product, you'll
find that they often have twice as many parts as the circuits on the
data sheets. These don't reflect bad engineering -- they show what some
engineer found he/she had to do to get the darned thing to work!
--
Ring the bells that still can ring
Forget the perfect offering
There is a crack in everything
That's how the light gets in -- Leonard Cohen
--
Lee A. Hart, 814 8th Ave N, Sartell MN 56377, leeahart_at_earthlink.net
--- End Message ---
--- Begin Message ---
Steve Peterson wrote:
So just out of curiosity, how does one detect the ten nano, 800 volt
spikes? Faster scope? Just assume they're going to be there and design
accordingly?
Yes, that's one way to do it. Many circuits include parts for
"insurance". X shouldn't happen, but if it does, it won't kill something.
The other problem is that instrumentation around high power electronics
often behaves strangely, and "lies" to you. You can hook the ground and
the center lead of your scope to the same pin, and *still* see voltage
spikes with the big transistors switch! They aren't really there (since
the 'scope input is shorted); but it warns you that you can't always
believe your instruments!
--
Ring the bells that still can ring
Forget the perfect offering
There is a crack in everything
That's how the light gets in -- Leonard Cohen
--
Lee A. Hart, 814 8th Ave N, Sartell MN 56377, leeahart_at_earthlink.net
--- End Message ---
--- Begin Message ---
Adrian DeLeon wrote:
Before I plunk down $500+ on a DC/DC that can handle 450W at 110V
nominal, I was wondering:
If I paralleled two DC/DC converters, each connected to (almost)
1/2 the pack, how bad would it alter the balance of my pack? I'm
running 19 T-105s, so it's a 9/10 split on the batteries.
It can be done. You would need to have some method to make the two
DC/DC's share the load appropriately; but that's not hard. In this case,
"appropriately" means so each draws the same current from its half of
the battery pack, even though the two packs have different nominal voltages.
I would try a variation of my Batt-Bridge circuit; three LEDs and two
resistors. One LED will light if the upper half-pack is low; the other
if the lower half-pack is low. The resistor values set the balance point.
Make these LEDs the ones inside an optocoupler, and use the
phototransistors to bias the output voltages of each DC/DC so they share
the load to keep each half-pack at equivalent voltages per cell.
--
Ring the bells that still can ring
Forget the perfect offering
There is a crack in everything
That's how the light gets in -- Leonard Cohen
--
Lee A. Hart, 814 8th Ave N, Sartell MN 56377, leeahart_at_earthlink.net
--- End Message ---
--- Begin Message ---
Need more battery volts and your PM motors are now becoming your Enemy.
Adjust your gear ratio to lug the motor some.. Like take one tooth out of
the motor sprocket or take about 5 to 10 out of the wheel sprocket, Like
about %10 Diff ratio.
That should hand you the upper track speed.
Or of your last 24 volts becomes... a resistor.. Yea New lead.
But keep in mind the PM motors have a brick wall in thier rpm to volts plot.
Have that much consistancy tells me you are hitting some kind of limit. The
Lead is not that specific , But a PM motor running out of enough volts to
keep it drawing is.
Better lead and %10 lower ration(lower numeric). Should really help.
You ARE impressing me with PM motors.. But a Series motor is simply desinged
to do what you are doing, a PM is NOT.
Still have not tried a 8 incher.. and a bit of brush timing magic????
That's ALL Dewane's bike has, and a old 1200 amp Raptor.
You have a Zilla... a PM... You don't want to see what they can do with
Fresh lead and a Z2K.!!
Madman.
Hat... Bit of Salt some pepper.. Steak seasoning.. Broiled.. ..It can be
tastey!!
But not yet.
The fast 100+ runs they did were pure simple Brass Balls runs Hot lead, and
everything they had hung out. I was there... they roasted the lead with my
PFC50 trying to get more heat, That they did a checked off that pack!
Steve Kaiser ...Bike owner.had Dwean do a good burn off.. it's needed to
make a good stick at the launch.. PM??? can you Even bake them off in the
box??
----- Original Message -----
From: <[EMAIL PROTECTED]>
To: <ev@listproc.sjsu.edu>
Sent: Thursday, May 24, 2007 6:53 PM
Subject: Re: AGNS misses 168 record
Chip,
As you know the ev drag racing bugs are like those on a windshield in
Florida in May.
Solving new and different problems is really part of the allure to me.
Speaking of records, after last night I have even more respect for that
168 volt MT #.
I told Rudman he would eat his hat and I got mine handed to me.
Weds night???
Shawn
-----Original Message-----
From: Chip Gribben <[EMAIL PROTECTED]>
To: ev@listproc.sjsu.edu
Sent: Thu, 24 May 2007 5:05 pm
Subject: Re: AGNS misses 168 record
Hey Shawn! Please don't break anything else before the race. And save
us a few records too :-)
Actually, this is probably good. You are getting all the bugs worked
out before the event. So OK, that's fine.
Good luck!
Chip
On May 24, 2007, at 12:59 PM, Electric Vehicle Discussion List wrote:
>
> From: [EMAIL PROTECTED]
> Date: May 24, 2007 8:03:16 AM EDT
> To: ev@listproc.sjsu.edu
> Subject: AGNS misses 168 record
>
>
> Wednesday was a day of anomalies.
>
> 1. The Electropolitan twists up her driveshaft at 50 MPH.
> 2. A Bat reg catches fire.
> 3. Perfect weather in Thompson OH wih no wind, no clouds, and 87 >
degrees.
> 4. AGNS runs a 12.888 at 103, a 12.818 at 103, and a 12.888 at 103.
> 5. AGNS runs 95 MPH in the 1/8 only to fall on her face 3 times and >
limp to 103 MPH in the 1/4
> 5. A Zilla hairball fails after run 2 with a bad internal connection.
>
> All in all just a weird but fun day. About the 168 runs:
> It became apparent after 1 run that the 2 batteries I stole from >
the Metro to bump AGNS' volts to 168 were not on the same cycle > path
as the other 12. I cycled them through and brought up to temp > 3 times
before we went to track but after run #1 when I talked to > Denis,
looked at the time slip, measured battery temp, and watched > the bats
fill back up it was painfully clear they were not up to > snuff. AGNS
roared out to 95 in the 1/8th them fell asleep 3 times > to finish at
103. Compare this to Saturday when she only ran 81 in > the 1/8th and
pulled all the way to 106 in the 1/4. My fault. We > finished our first
two runs at 7:30, recharged and were in line for > eliminations when
the hairball connection failed. We checked > everything but could not
get the main contactor off light to glow. > By the time I found that
the plug for the 2 voltage inputs was > loose it was too late, we
missed our turn and were out. Too bad > because with times of 12.888,
12.817 , and 12.888 I would say we > were dead consistent. We finally
got a consolation run at 10:30 > pm. I taped up the hairball to put
enough pressure on the input > plug to make it work and we ran exactly
the same time again. Who > wants consistently slow? Not me. Give me a
1/2 second breakout any > day! A real life lesson that once again
proves....
> IT'S THE BATTERIES STUPID!
>
> Shawn
________________________________________________________________________
AOL now offers free email to everyone. Find out more about what's free
from AOL at AOL.com.
=0
--- End Message ---
--- Begin Message ---
Just cut your losses, its more efficient that way ;-P
On the car too. But hey, 188 mpg is quite appealing, with a 12 second 1/4 mile
to boot :-)
----- Original Message -----
From: Tim Humphrey <[EMAIL PROTECTED]>
Date: Friday, May 25, 2007 6:52 am
Subject: RE: Fast and Eff!!! Re: White Zombie gets to 'test' drive Lithium!
To: EV <ev@listproc.sjsu.edu>
>
>
> So, doing the math....
>
> 165Wh per mile.
>
> 38 KWh per gallon_energy.
>
> 38000/165 = 230 mpg_energy.
>
> $.10 per KWh.
> $3.10 per gal.
> == 31kWh per gal_$$
>
> 31000/165 = 187.87 mpg_$$
>
>
> I'm not a mathemetician. I hope I didn't screw it too bad. I'm
> sure it will be corrected if I did. ;-)
>
> I will take any corrections as a learning experience, maybe
> improve myself 5% while I'm at it ;-)
>
>
> --
> Stay Charged!
> Hump
> I-5, Blossvale NY
>
>
>
>
>
> > -----Original Message-----
> > From: [EMAIL PROTECTED] [mailto:owner-
> [EMAIL PROTECTED] On
> > Behalf Of John Wayland
> > Sent: Friday, May 25, 2007 10:33 AM
> > To: ev@listproc.sjsu.edu
> > Subject: Re: Fast and Eff!!! Re: White Zombie gets to 'test' drive
> > Lithium!
> >
> > Hello to All,
> >
> >>--- jerryd <[EMAIL PROTECTED]> wrote:
> >>
> >>
> >>>You forgot an important number, it took only
> >>>140-150
> >>>wthr/mile for it's trip!! Not bad for an EV
> >>>breathing down
> >>>the 11 sec 14 mile bracket!!
> >>>
> >
> > Yes, I agree that it's pretty good efficiency for such a
> powerful car,
> > but remember the drive was at slower speeds through a 35 mph
> posted area
> >
> > and a 45 mph posted area. It's easier to get good numbers driving
> > slower. As you know, whrs per mile go up at highway speeds as
> aero drag
> > comes into play, and highway speeds are usually the way whrs per
> mile> are figured.
> >
> > White Zombie's twin 'Blue Meanie' has the losses of a tranny to deal
> > with, but weighing less at 2340 lbs. and with its narrow LRR tires
> > pumped up to 50 psi, it gets about 165 whrs per mile at a steady
> 60 mph.
> >
> > White Zombie has no tranny losses, but it does weighs 240 lbs.
> more and
> > has those not-so-range friendly fat rear tires plus the drag of
> a Ford 9
> >
> > inch differential's inefficient (but very robust) offset pinion. I'd
> > guess that with the rear tires pumped up to 35 psi (drag racing
> psi is
> > lowered to ~ 16) White Zombie will probably consume 180-190 whrs per
> > mile at 5
>
>
--- End Message ---
--- Begin Message ---
I agree that people should use properly rated contactors for the maximum
voltage they plan to use. I am asking to learn the principals, if a
contactor is rated for 72V at 200 amps that means it should be able to
safely open a circuit pushing 200 amp through it at 72 volts right? If a
properly sized capacitor is placed across the main contacts to be used
as a snubber there is less chance of DC current following an arc across
the contacts. So could a 72V contactor be used in a little higher
voltage application as long as the amps were still within ratings? Again
I am not condoning the use of under rated contactors.
Another thing occurs, when the contactor closes the capacitor discharges
giving the contactor that current needed to seat the contacts or am I
off on that theory as well?
Thanks,
Nate
-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On
Behalf Of Lee Hart
Sent: Thursday, May 24, 2007 8:52 AM
To: ev@listproc.sjsu.edu
Subject: Re: Main Contactor Ebay Search Criteria
England Nathan-r25543 wrote:
> Just curious what a capacitor across the main contacts would do as arc
> suppression.
"Snubber" circuits work no matter what the size of the contacts or load.
For a little 120v 1amp switch, a 0.1uF capacitor and 100 ohm resistor
is about right (that's what you'll find in all sorts of consumer
products).
For the main contactor in my ComutaVan (72v, 200amps), I used a 2000uF
capacitor with 24" of #18 wire as the resistor. This considerably
reduced arcing.
You'll still have to deal with the insulation strength and open contact
spacing -- they have to good for the voltage you are trying to switch.
For example, a single contact will need 1/2" or more spacing at 120vdc.
You might be able to adjust the open contact spacing this large, but
then the solenoid probably can't pull it in without a considerably
higher coil voltage.
--
Ring the bells that still can ring
Forget the perfect offering
There is a crack in everything
That's how the light gets in -- Leonard Cohen
--
Lee A. Hart, 814 8th Ave N, Sartell MN 56377, leeahart_at_earthlink.net
--- End Message ---
--- Begin Message ---
Since you're a fellow Pinninfarina EV'er I added you to my blogroll
www.electric-lemon.com
On 5/25/07, Tony Furr <[EMAIL PROTECTED]> wrote:
Greetings all-
The site for my Lancia Scorpion Elettrico is finally ready for prime-
time. You can find it here:
www.plugzen.com
After finally making it to a SEVA meeting last month, I had new found
inspiration to get this thing completed. It includes a journal that I
try to update regularly and photo galleries I will continue to expand
(especially with Gasless on Greenwood picks). I could also use some
help filling out the links section if there are good EV info sources
I've undoubtedly missed. There's also an RSS feed for those of you
into the automated info thing.
Please check it out and let me know what you think...and send it
along to anyone else you think might be interested.
-t
--- End Message ---
--- Begin Message ---
So, does anyone have any figures on how much power it actually takes to drive
A/C and/or power steering?
Bill
--- End Message ---
--- Begin Message ---
[EMAIL PROTECTED] wrote:
So, does anyone have any figures on how much power it actually takes to drive
A/C and/or power steering?
Bill
I can't find any information on the BTU/h ratings of car A/C systems,
but 1HP = 9,900 BTU/h. A smallish 1-room in-window home A/C unit is
rated around 8,000-10,000 BTU/h, and I doubt many cars have output
greater than that (or even approaching that level since they are cooling
a smaller volume). I can't find any efficiency ratings for car A/C
units, but I imagine they are not terribly efficient. I would be pretty
confident with a motor that could output 2HP continuously, but this is
all just theoretical musings. Sorry I couldn't find any more exact
information, but I wanted to get the discussion going a little.
Also, wikipedia (take this with a huge grain of salt since it is
wikipedia) says an automobile A/C system uses "around 5 hp of the
engine's power."
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A/C can be driven ok off a 1 hp motor. P/S, however pulls a lot of power on
turns. It takes almost nothing when no steering is taking place. Both
together at the same time would require a substantial drive motor. So the end
of the traction motor seems the best choice to me.
The other alternative used is a hydraulic electric steering pump like the
Toyota MR2 and some 80's Chevrolets used. There are also some European cars
that had them. They are widely used by EV'ers ( Check with Ryan at EVSource
and he can tell you about his). You can cause this to run only when you turn,
saving drain on your 12v side. If it is a Rack and pinion steering,
installing sensor switches will to the trick.
Look on EBAY. There is a dealer that sells them. Do a search for electric
hydraulic steering or electric steering and it will usually pop up some results.
Mark Ward
95 Saab 900 SE "Saabrina"
www.saabrina.blogspot.com
---- [EMAIL PROTECTED] wrote:
> So, does anyone have any figures on how much power it actually takes to drive
> A/C and/or power steering?
>
> Bill
>
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On 5/25/07, Mark Ward <[EMAIL PROTECTED]> wrote:
The other alternative used is a hydraulic electric steering pump like the
Toyota MR2 and some
80's Chevrolets used. There are also some European cars that had them.
Yes, my Citroen factory EV has this unit:
http://tinyurl.com/2adld7
(ebay item 120120400351)
As it says, this is a standard component of a very ubiquitous range of
small ICE cars in Europe, so it's widely available, and works with a
standard hydraulic steering rack. The unit tends to out-last the rest
of the car.
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This is the auto industries grassroots campaign to derail proposed new CAFE
standards. Go and leave a proCAFE message instead. Those idiots probably
don't proof them all (any more than they actually get read at the receiving
end). It may do no good, but I sure felt better leaving my note on their BS
website.
Here's my message:
I currently drive a Toyota RAV4 EV (electric vehicle).
It's EPA rated at 116 miles per gallon.
Now, Toyota stands with American automakers in their misguided fight to
derail attempts to improve our transportation energy situation.
Back in 1993, a company called Unique Mobility (now UQM on the ticker)
converted a HumVee to diesel-electric hybrid. This 8 ton vehicle could
travel 25 miles EV only, and with the engine running, got 30mpg.
Andy Frank/UC Davis, converted a Chevy Suburban to hybrid and it got 35mpg.
If these people (not automakers) can get this type of mileage performance
out of these vehicles, obviously the carmakers are lying and/or dragging
their feet.
Please support any and all efforts to strengthen CAFE standards and increase
minimum mileage requirements for US vehicles.
National security should trump automakers' bottom line- but will it?
Sincerely,
J. Marvin Campbell
--
MarvyMarv
aka
Mo'Nilla
"The Stone Age did not end for lack of stone, and the Oil Age will end long
before the world runs out of oil."
- Sheikh Zaki Yamani
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I have instruments on all my accessory drive units. The power steering at a
continuous running is about 12 volts at 12 amps. It is a power steering
unit from CanEV which can be adjusted down to a minimum load.
The A/C unit which is a surface mount type for a GMC has a starting ampere
at 60 volts at 44 amps. Have two 1.75 continuous duty motors which have a
peak hp of 3 hp, which makes 3.5 hp running or 6 hp peak.
HP = (60 v x 44 A)/746 = about 3.53 hp every time the A/C clutch engages,
then it levels down to about 10 amps at 60 volts which is just less than 1
hp.
To prevent the starting surge of any of my accessory units, my main motor
pilot shaft connects to the accessory drive system using another A/C clutch
during start up and during coast down of the EV.
Roland
----- Original Message -----
From: "electro" <[EMAIL PROTECTED]>
To: <ev@listproc.sjsu.edu>
Sent: Friday, May 25, 2007 12:11 PM
Subject: Re: Electric motor for air conditioning or power steering
> [EMAIL PROTECTED] wrote:
> > So, does anyone have any figures on how much power it actually takes to
> > drive A/C and/or power steering?
> >
> > Bill
> >
> >
> I can't find any information on the BTU/h ratings of car A/C systems,
> but 1HP = 9,900 BTU/h. A smallish 1-room in-window home A/C unit is
> rated around 8,000-10,000 BTU/h, and I doubt many cars have output
> greater than that (or even approaching that level since they are cooling
> a smaller volume). I can't find any efficiency ratings for car A/C
> units, but I imagine they are not terribly efficient. I would be pretty
> confident with a motor that could output 2HP continuously, but this is
> all just theoretical musings. Sorry I couldn't find any more exact
> information, but I wanted to get the discussion going a little.
>
> Also, wikipedia (take this with a huge grain of salt since it is
> wikipedia) says an automobile A/C system uses "around 5 hp of the
> engine's power."
>
>
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From: England, Nathan
> I agree that people should use properly rated contactors for
> the maximum voltage they plan to use. I am asking to learn the
> principals; if a contactor is rated for 72V at 200 amps that
> means it should be able to safely open a circuit pushing 200
> amp through it at 72 volts, right?
The ratings are really a set of curves; not a simple number. The manufacturer
usually gives one (and sometimes several) data points on these curves. For
example, "72vdc at 200amps for 100,000 cycles".
If you run a higher current and/or voltage, the life will be shorter. A small
change (say, 96vdc at 300amps, i.e. twice the power) might only halve the life
to 50,000 cycles. There is twice as much energy in the arc as it opens and
closes, so each one does twice the damage to the contact.
At higher currents, you also run into thermal limitations. The contactor might
be rated at 200amps continuously at 70 deg.C. At 300amps, it might have to be
reduced to 40 deg.C maximum, or a 50% duty cycle at 70 deg.C.
At some point, a single arc will do so much damage that it alone will destroy
the contacts. This is the interrupting capacity. For the above contactor, it
might be spec'd at 120vdc at 1000amps *once*! This could be when the contactor
opens under load to stop a car with a shorted controller.
> If a properly sized capacitor is placed across the main contacts
> to be used as a snubber, there is less chance of DC current
> following an arc across the contacts. So could a 72V contactor be
> used in a little higher voltage application as long as the amps
> were still within ratings?
Snubber circuits alter the power factor of the load, as seen by the contactor.
An inductive load is easy to turn on (current is low immediately following
turn-on, and slowly ramps up), but hard to turn off (current stays high for a
significant time after turn-off). Adding the capacitor increases the turn-on
current but decreases the turn-off current, and so extends contact life. It
does not extend the voltage rating; it just makes the contacts last longer at a
given voltage.
There are *lots* of snubber circuits. Engineers have had many years to develop
them. Some of course work better than others (and consequently cost more).
--
I would not waste my life in friction when it could be turned into momentum. --
Frances Willard
--
Lee Hart, 814 8th Ave N, Sartell MN 56377, leeahart_at_earthlink.net
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Here is a link to an EV with a DC motor like the one I originally was going to
use on my project
http://www.metricmind.com/ac_honda/images/ac1.jpg
---- [EMAIL PROTECTED] wrote:
> So, does anyone have any figures on how much power it actually takes to drive
> A/C and/or power steering?
>
> Bill
>
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People have said 20,000 BTU for a car. Depends on the size, make, and
model of car I'm sure. Some cars are twice as big as others for starters.
There's not a straight hp-BTU relationship. Not only does efficiency
vary a lot, but the electrical load increases as the temp differential
between evaporator and condenser increases. At least it did in my
experience of measuring power on a window unit. Unless you can slow
down the motor during worst-case situations, it will have to be
oversized to accomodate those situations rather than average power.
I think 5 HP is about right.
Electric air conditioners normally get a "free ride" by using the
coolant flow to cool the motor. This not only improves cooling but
guarantees a consistent maximum operating temp so they can be sized
fairly small. An external motor doesn't get that.
Seems to me the best thing would be to take apart a big-ass window unit,
put the condenser where the radiator went, use the stock evaporator
core, and use the window unit's motor driven by a special power
inverter. It'd have to be special in that it needs a buck-boost
converter to take a variable battery high voltage and make 110V-220V.
Actually it can also pull some tricks like adjusting the AC output
voltage for optimum motor efficiency. Might gain 15%-20% doing that.
Such an inverter would not be as complicated as the main motor
controller due to the reduced size, but complicated nonetheless.
Actually I take that back, technically it's more complicated due to the
topology, but with the much lower current the output stage is going to
be cheaper and easier to build even though it's AC and thus must have 4
transistors at least instead of one.
Danny
electro wrote:
[EMAIL PROTECTED] wrote:
So, does anyone have any figures on how much power it actually takes
to drive A/C and/or power steering?
Bill
I can't find any information on the BTU/h ratings of car A/C systems,
but 1HP = 9,900 BTU/h. A smallish 1-room in-window home A/C unit is
rated around 8,000-10,000 BTU/h, and I doubt many cars have output
greater than that (or even approaching that level since they are
cooling a smaller volume). I can't find any efficiency ratings for car
A/C units, but I imagine they are not terribly efficient. I would be
pretty confident with a motor that could output 2HP continuously, but
this is all just theoretical musings. Sorry I couldn't find any more
exact information, but I wanted to get the discussion going a little.
Also, wikipedia (take this with a huge grain of salt since it is
wikipedia) says an automobile A/C system uses "around 5 hp of the
engine's power."
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There are all kinds of tricks. Separate supplies, Charge pumps,
transformers, etc.
There are a lot of "cool tricks" explained on 4QD's site....
On some of his simpler controllers, which are T-bridges with a high side
(bat to motor) and a low side (motor to motor/regen) he uses N type for both
sides, even though you need a gate drive for the high side that's ~9 volts
OVER the battery supply voltage. He uses a diode/capacitor charge pump to
create this voltage. Super-simple, but works well.
Again, if you wanna learn about this stuff, very good reading there!
-Phil
----- Original Message -----
From: "Peter VanDerWal" <[EMAIL PROTECTED]>
To: <ev@listproc.sjsu.edu>
Sent: Friday, May 25, 2007 8:26 AM
Subject: Re: How regen works
I've heard this, I just don't quite understand how you keep them turned on
when they are reversed.
As I understand it (and it's been a couple years since I played with
them), for an NPN Mosfet to conductm the gate has to be approx 10V more
positive than the drain (unless you are using one of those 'spensive
FETs).
If it's reversed, then won't the drain have to go to a higher voltage than
the source side? I.e. 10V higher voltage than your pack voltage?
I can see how you could do this, but it would take more than just a
programming upgrade.
MOSFETs will conduct either direction when ON. One direction when OFF
due
to the body diode.
So Whenever you want to improve efficiency by taking the body diode
voltage
drop out, you can just switch the gate on and let it bypass the body
diode.
Software can do this at the right time and you get synchronous behavior.
-Phil
----- Original Message -----
From: "Peter VanDerWal" <[EMAIL PROTECTED]>
To: <ev@listproc.sjsu.edu>
Sent: Thursday, May 24, 2007 5:46 PM
Subject: RE: How regen works
..aren't very good diodes, so if a controller uses them, the maximum
regen
current won't be as high as the maximum motoring current.
Unless you use synchronous rectification - which uses the MOSFET in
reverse. You probably want to do that anyways to lower the losses.
Can you explain this? The few synchoronous rectification designs I've
studied used a second MOSFET to relace the diode. I haven't seen any
that
use a single MOSFET for both functions.
I.e. for a PMDC motor controller, instead of one FET and one diode, they
use a high side FET and a low side FET.
I had assumed they'd do the same thing with three phase synchronous
rectifiers.
--
If you send email to me, or the EVDL, that has > 4 lines of legalistic
junk at the end; then you are specifically authorizing me to do whatever
I
wish with the message. By posting the message you agree that your long
legalistic signature is void.
--
If you send email to me, or the EVDL, that has > 4 lines of legalistic
junk at the end; then you are specifically authorizing me to do whatever I
wish with the message. By posting the message you agree that your long
legalistic signature is void.
--- End Message ---
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("NPN" is a type of bipolar transistor- a MOSFET transistor is N-channel
or P-channel)
The body diode is an inherent part of the MOSFET design. Actually it's
an annoying limitation in many situations, but it's not put there by
choice, it's a part of the structure.
It is typically not a great diode because it's not especially fast.
Slower diodes will increase the heat. Also as a diode it will have a
drop of 0.7v, or more at high currents. There are exceptions though,
some special transistors even include a second high speed Schottky diode
in parallel with the intrinsic diode inside the package.
The extra heat from using the intrinsic diode to carry current is rough
because the heat ends up in the transistor, which is typically already
needing expensive measures to keep cool.
Also, one other prob- 2 diodes can't be put in parallel because
whichever one warms up first turns on at a lower voltage, thus more of
the current and getting warmer still until it ends up bearing the entire
load and burns up. MOSFETs have no such problem paralleling in their
normal forward-bias on-state because their on-state resistance increases
with temp, generally shifting the current over to the colder
transistor. However, the current through the intrinsic diode suffers
the same paralleling problem as parallel diodes. The problem's at least
partially compensated by the way the heat generated from the
forward-bias on-state tends to shift away from the hotter transistor to
balance out their temps, but it's still sort of a fight.
Danny
Dale Ulan wrote:
As I understand it (and it's been a couple years since I played with
them), for an NPN Mosfet to conductm the gate has to be approx 10V more
positive than the drain (unless you are using one of those 'spensive
FETs).
It needs to be 10V more positive than the source, not the drain.
But in any case, when running the MOSFET in reverse, the diode is
conducting. Let's use the bottom-side MOSFET. So the source is
at 0V, and the drain is at -0.7 volts (the motor's inductance plus
the diode drop creates this). The MOSFET will happily conduct in
reverse if the drain is within a volt either way of the source,
when you turn it on. So when you apply 10V (gate to source)
the FET turns on, and the voltage on the drain of the FET drops
to - (Iwinding * Rdson). For, say, a 50 amp current and a .005
ohm Rdson, you'll get -0.25 volts on the drain of the FET relative
to the source.
The key to synchronous rectification is that the MOSFET diode would
have been on anyways, creating a -0.7 volt drop (or thereabouts).
Turning on the MOSFET just lowers that drop providing that Rdson
is low enough.
In ICE engine controllers, it is common to use a P-channel FET in
reverse for reverse polarity protection to prevent the engine
management computer from blowing up in the case of a reverse voltage.
How that works is identical to synchronous rectification.
-Dale
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