EV Digest 2687
Topics covered in this issue include:
1) Re: motors with no magnetic fields.
by David Dymaxion <[EMAIL PROTECTED]>
2) Re: Buck converters, Correction.
by Otmar <[EMAIL PROTECTED]>
3) Re: motors with no magnetic fields.
by Peter VanDerWal <[EMAIL PROTECTED]>
4) Re: motors with no magnetic fields.
by [EMAIL PROTECTED]
5) RE: Outlets (was That time of the year again...)
by "Tim Clevenger" <[EMAIL PROTECTED]>
6) Re: motors with no magnetic fields.
by Peter VanDerWal <[EMAIL PROTECTED]>
7) Re: motors with no magnetic fields.
by [EMAIL PROTECTED]
8) Re: Buck converters, Correction.
by Peter VanDerWal <[EMAIL PROTECTED]>
9) RE: motors with no magnetic fields.
by "Andre Blanchard" <[EMAIL PROTECTED]>
10) Re: Buck converters (was Re: AC controllers)
by Paul G <[EMAIL PROTECTED]>
11) Re: AC controllers
by "Philippe Borges" <[EMAIL PROTECTED]>
12) RE: Buck converters, Correction.
by "Andre Blanchard" <[EMAIL PROTECTED]>
13) RE: Outlets (was That time of the year again...)
by "Andre Blanchard" <[EMAIL PROTECTED]>
14) MagneChargers outdoors
by "Christopher Zach" <[EMAIL PROTECTED]>
15) Re: motors with no magnetic fields.
by "garry" <[EMAIL PROTECTED]>
16) RE: MagneChargers outdoors
by "Melanie Savage" <[EMAIL PROTECTED]>
17) Bassoonist in San Francisco wants Insight or other long range EV
by "Lawrence Rhodes" <[EMAIL PROTECTED]>
18) Re: Bassoonist in San Francisco wants Insight or other long range
EV
by Carmen Farruggia <[EMAIL PROTECTED]>
--- Begin Message ---
Heh heh, pretty good.
Here is a real-life electric motor without magnetic fields:
<http://www.eskimo.com/~billb/emotor/emotor.html>. Note the lack of
power robbing iron to route the magnetic flux.
Might be just the solution for Li-ion lovers, you could string
together 2000 or so AAA cells to power the motor. Or better yet,
drive by rubbing a cat, or just drive fast on a low humidity day.
--- Peter VanDerWal <[EMAIL PROTECTED]> wrote:
> I was reading about the loses in a motor and one of them was
> Magnetic
> Loses. I figured I could make a more efficient motor if I could
> eliminate magnetic loses.
> The best way to eliminate magnetic loses is to eliminate the
> magnetic
> fields in a motor and I figured out how to do it.
>
> What I do is use the "equal and Opposite" theory to eliminate the
> magnetic fields. You see a magnetic field has a strength that is
> measured in what I call Woggles. 1 Woggle is equal to the field
> created
> by a coil with 1V @ 1A running through it.
>
> I figured if I create two magnetic fields that are opposite of each
> other and of equal strength they will cancel each other out. I
> tried it
> and it works!!
> You can see pictures of my motor at
> http://www.SomeStupidWebsite.ha.ha.
>
> To make sure that the magnetic fields were canceled out I used a
> piece
> of steel. Now we all know that steel is attracted to magnetic
> fields.
> I first held up the piece of steel to the end of my motor with no
> power
> applied and it didn't stick. I figured this would happen because
> with
> no power applied the motor has no magnetic fields. Then I powered
> up
> the motor and held the steel to the end again and it still didn't
> stick. This is proof that there are no magnetic fields in the
> motor.
>
> The motor only weighs about 50 lbs, but it's very efficient, in
> fact it
> must be over 100% efficient. I know this because I attached the
> motor
> to a shopping cart and climbed inside and it moved the cart around
> at
> about 2 mph with what I guess was only 50 watts of power. Now we
> all
> know that 50 watts of power simply isn't enough to move over 300
> lbs
> worth of me, motor, batteries, and cart, so it must be REALLY
> efficient.
>
> And to prove it I felt the motor afterward and it wasn't even hot.
>
> Pretty cool huh?
>
> P.S. For those who are humor impaired the above was just an example
> for
> Garry to show that if you don't understand how something works you
> can
> easily misinterpret the results to prove that your theory, no
> matter how
> ridiculous, is right.
>
=====
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--- End Message ---
--- Begin Message ---
Buck converters are what we all run in our EVs, and describing them
is a bit of a task, so I'm very happy to see that Peter has taken the
time to describe them. I'm thinking a revised version of this
document would be excellent to have in the EV Faq.
With that said, I see what looks to me as a error in the description.
It is being described as if the inductor of the buck converter is
separate from the motor, while in fact it is integral to the motor.
Therefore the voltages and currents in the motor include those of the
inductor. The same issue comes up a few times, I will note them in
the text. Also, may I be so bold as to add a few words that I think
may make it clearer to some?
A PWM Buck converter needs four main components.
A input filter capacitor
A switch (usually a power transistor of some kind)
A freewheeling diode
and an inductor (the motor in this case)
Now for a little electronics basics:
A capacitor resists a change in voltage. It does this by absorbing
voltage that is higher than it's current charge and supplying voltage
when the voltage drops below it's current charge.
An inductor resists a change in current. What happens when you
initially try to push current through an inductor is that this creates
an expanding magnetic field. This expanding field creates EMF in the
coil that resists the creation of the field and the flow of current. So
the current doesn't just instantly start flowing, it builds up slowly
(talking microseconds here), until it reaches what ever current the
circuit will allow (in a DC circuit this is limited only by resistance).
When you shut of the current the magnetic field in the inductor starts
to collapse. This also creates EMF, only this EMF doesn't fight the
current but is of the opposite polarity and tries to keep the current
flowing.
If there is no path for the current the the voltage across the coil
builds up
to thousands of volts
in an effort to force current to flow, this is what causes
arcing of contacts.
If there is a path for current to flow (like a diode) then the current
continues to flow and slowly decays (due to the resistance in the
circuit)
OK back to the Buck converter.
When the switch turns on, the motors inductance initially fights the
flow of current but eventually (again microseconds here) current starts
flowing. When the voltage builds up to the desired level the switch
turns off.
What is building up is current, not voltage. The voltage on the motor
is a square wave with a high of the full battery voltage and a low of
zero (actually -1V due to the diode drop in the freewheel path)
The way the freewheeling diode is installed it is reverse biased by the
voltage through the switch (so you don't waste any power in it).
When the switch turns off the motor's inductance wants the current to
keep flowing. It is actually trying to draw, or suck current.
The path for this current is through the freewheeling diode, which now
ends up forward biased by the motor sucking current.
Naturally since noting is creating this current flow except the
collapsing field in the motor, it starts to decay and the voltage starts
dropping.
Current decays, voltage on motor stays at -1V.
Before it gets too low the switch turns on again and current flows into
the motor and it's voltage starts building up again.
Current builds up, not voltage.
Now on the battery side of the switch what you see is a huge current
draw, and then nothing, and then huge current, etc.
This current is equal to the current in the motor (you see that right?)
The input capacitors charge up to the battery voltage and try to keep
the voltage stable. They do this by sourcing current when the demand
quickly jumps up and drawing current from the batteries (to recharge
their voltage) when the load drops off. The net result is that they
even out the current that appears at the batteries.
So the large current spikes get sourced by the capacitors and the
battery sees a current that is equal to the time averaged current going
through the switch. In other words if the switch is passing 100 amps
when it is on and zero amps when it is off and it is on 50% of the time,
then the filter caps make this look to the batteries like a constant 50
amps draw.
The, motor on the other hand, is seeing 100 amps but the
average
voltage across
it is only about 1/2 the batteries voltage. This is because the switch
is only turned on half the time
so it's voltage never gets to build up
to full pack voltage.
Strike this.
The net result is that power out(volts x amps) = power in minus losses.
The losses are because none of the components are perfect. We lose a
little power in each of them, from the capacitor to the diode.
If you change the duty cycle to 25% on, then the
average
motor voltage is only
25% of the pack voltage. The difference between the two voltages is
higher so when the switch turns on a higher current tries to flow. Net
result is that current in the motor is almost four times what the
batteries see.
If you look at the motor voltage with an O-scope, you will see a DC
voltage with a small AC sawtooth on top. This saw tooth is the voltage
charging up and decaying when the switch turns on and off.
This is what you see if you look at the current. It is the current
charging up and down. The voltage will be a square wave.
If you measure the voltage on the input side of the capacitors you will
see a DC voltage with a small saw tooth on it. This saw tooth is caused
by the capacitors charging and discharging. Measuring the current here
you will see a DC current with a saw tooth (the capacitor isn't
perfect).
Measure the current at the switch and you will see an on/off current at
what ever duty cycle the controller is running at.
Everybody is happy (except Garry) the laws of physics are intact, and
everything operates they way it is supposed to according to accepted
electronics theory.
> I'm still trying to understand how the PWM controller acts as a DC
> transformer ( using the DC to DC Buck converter principle?) to put all
> those extra electron to the motor. Are there any good tutorial type
> references about this? Thanks,
So, Once again. Thanks to Peter for taking the time to describe the
buck converter. It's certainly a confusing subject. I think it would
be a great thing to have in the FAQ.
-Otmar-
http://www.CafeElectric.com/ New Zilla controllers, now available.
http://www.evcl.com/914 My electric 914
--- End Message ---
--- Begin Message ---
On Fri, 2003-03-28 at 12:02, Lonnie Borntreger wrote:
> On Fri, 2003-03-28 at 11:57, Peter VanDerWal wrote:
> > What I do is use the "equal and Opposite" theory to eliminate the
> > magnetic fields. You see a magnetic field has a strength that is
> > measured in what I call Woggles. 1 Woggle is equal to the field created
> > by a coil with 1V @ 1A running through it.
>
> You know, the least you could do is to clarify for those who aren't
> engineers.
>
> 1 Woggle = 1V @ 1A though a 1cm coil with 10 loops of 12g solid aluminum
> wire.
>
> Sheesh! Somebody might read your formula and assume that 1V @ 1A
> through ANY type of coil would equal 1 woggle.
>
>
But it DOES, that's the beauty of a Woggle. No complex formula's.
--- End Message ---
--- Begin Message ---
You see a magnetic field has a strength that is
> measured in what I call Woggles. 1 Woggle is equal to the field created
> by a coil with 1V @ 1A running through it.
>
I don't want to seem picky, but shouldn't that be 1A @ 1V?
Stay Charged!
Hump
--
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Sign-up for your own FREE Personalized E-mail at Mail.com
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--- End Message ---
--- Begin Message ---
While you're at it, go out every couple of years and watch your service
panel closely while someone plugs in your charger or kicks on the air
conditioning. I've been in two places, built fairly recently, where the
contacts on the circuit breakers had corroded to the point where sparks
could be seen and heard between the breakers when high loads were switched
on.
In my last apartment, an electrician ended up replacing the backplane and
several breakers due to corrosion, and in my current house, I've had to
replace two circuit breakers for the same reason. My house has the panel
out in the weather, and the apartment had the panel in the laundry room,
where humidity gets very high.
Tim
------
From : "Grannes, Dean" <[EMAIL PROTECTED]>
To : <[EMAIL PROTECTED]>
Subject :RE: Outlets (was That time of the year again...)
Date : Fri, 28 Mar 2003 09:59:29 -0800
The moral of the story is that if you have an outlet that you use every
day for prolonged charging near the rated limit of the outlet, unless
you know it's a beefy well-built outlet, it would be prudent to pull off
the faceplate (after cutting the power, of course) and visually inspect
the outlet every so often (yearly?). Or consider replacing it with a
heavy-duty outlet.
_________________________________________________________________
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--- End Message ---
--- Begin Message ---
On Fri, 2003-03-28 at 12:58, [EMAIL PROTECTED] wrote:
> You see a magnetic field has a strength that is
> > measured in what I call Woggles. 1 Woggle is equal to the field created
> > by a coil with 1V @ 1A running through it.
> >
>
>
> I don't want to seem picky, but shouldn't that be 1A @ 1V?
Dooh!, How could I be so foolish! Of course, you are right. No w I
have to update my hypothetical webpage.
FWIW: I just tried this experiment with a Standard ADC series wound
motor (No really, I did). The angle iron wouldn't stick to the motor
anywhere, clearly they figured out how to eliminate magnetic fields
before I did. Damn, there go my dreams of fame and fortune. :-(
--- End Message ---
--- Begin Message ---
----- Original Message -----
From: Peter VanDerWal <[EMAIL PROTECTED]>
Date: 28 Mar 2003 13:36:39 -0700
To: EV <[EMAIL PROTECTED]>
Subject: Re: motors with no magnetic fields.
> On Fri, 2003-03-28 at 12:58, [EMAIL PROTECTED] wrote:
> > You see a magnetic field has a strength that is
> > > measured in what I call Woggles. 1 Woggle is equal to the field created
> > > by a coil with 1V @ 1A running through it.
> > >
> >
> >
> > I don't want to seem picky, but shouldn't that be 1A @ 1V?
>
> Dooh!, How could I be so foolish! Of course, you are right. No w I
> have to update my hypothetical webpage.
>
> FWIW: I just tried this experiment with a Standard ADC series wound
> motor (No really, I did). The angle iron wouldn't stick to the motor
> anywhere, clearly they figured out how to eliminate magnetic fields
> before I did. Damn, there go my dreams of fame and fortune. :-(
>
That's OK Pete!
Here an idea for you!
Figure out how to make a motor run on fiber optics.
Fiber is so much more efficient than copper. If we could get a fiber motor to run,
then advanced batteries would no longer be an issue for EV's. And get rid of the steel
too. Use Lexan.
Stay Charged!
Hump
--
__________________________________________________________
Sign-up for your own FREE Personalized E-mail at Mail.com
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--- End Message ---
--- Begin Message ---
On Fri, 2003-03-28 at 12:42, Otmar wrote:
> >When the switch turns on, the motors inductance initially fights the
> >flow of current but eventually (again microseconds here) current starts
> >flowing. When the voltage builds up to the desired level the switch
> >turns off.
>
> What is building up is current, not voltage. The voltage on the motor
> is a square wave with a high of the full battery voltage and a low of
> zero (actually -1V due to the diode drop in the freewheel path)
Oops, there I go confusing reality with what I read with a volt meter.
Otmar is (as usual) correct.
Perhaps I should have said "Apparent" voltage measured with a
voltmeter? Naw, Otmar said it better.
But, just for those of you who don't have am O-scope, if you measure
this with a Voltmeter(set for DC voltage) you will see a voltage that is
roughly equal to the time-averaged voltage of this square wave.
Just goes to show you that even Geniuses like me can screw up
occasionally ;-)
--- End Message ---
--- Begin Message ---
That could actually work.
http://antwrp.gsfc.nasa.gov/apod/ap000526.html
Put mirrors in place of the blades in a turbine rotor. Use the fiber aim
the light at the blades on the rotor.
Andre' B. andre-at-usermail.com
If something cannot be defined, it does not exist.
Isaac Newton
-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]
Behalf Of [EMAIL PROTECTED]
Sent: Friday, March 28, 2003 2:35 PM
To: [EMAIL PROTECTED]
Subject: Re: motors with no magnetic fields.
----- Original Message -----
From: Peter VanDerWal <[EMAIL PROTECTED]>
Date: 28 Mar 2003 13:36:39 -0700
To: EV <[EMAIL PROTECTED]>
Subject: Re: motors with no magnetic fields.
<< snip >>
That's OK Pete!
Here an idea for you!
Figure out how to make a motor run on fiber optics.
Fiber is so much more efficient than copper. If we could get a fiber motor
to run, then advanced batteries would no longer be an issue for EV's. And
get rid of the steel too. Use Lexan.
Stay Charged!
Hump
--
__________________________________________________________
Sign-up for your own FREE Personalized E-mail at Mail.com
http://www.mail.com/?sr=signup
--- End Message ---
--- Begin Message ---
Garry wrote:
First how do you see the removal of power out (amps x volts ) effecting
shaft output in your scenario and second if you know that there is output
from a spinning motor what would happen to efficiency figures if you were
able to remove this usefully and use it to charge a battery ?
There have actually been some motors built to do this. They where
used in the New York area to power neon transformers when the area
was still on a DC grid. These motors have both the regular comm and
brush set up, and two slip rings connected to opposite commutator
bars (well, I couldn't see exactly what comm bars they where
connected to).
So I know something about what happens when you try to remove power
from a motor. The power input to run the motor goes up. The motor
takes just a little power to run with no load (including no
connection to the output slip rings). When you attempt to use power
from those slip rings the input power to the motor by the output
power received.
A few of these motors had an output shaft on them too. If I put a
load on the shaft it increased the motors power consumption, over
what it already was running a neon lamp. So know I know that I can't
take the same power off the motor as electricity and off the motor as
shaft power too. Taking power off as electricity increases the input
power a similar amount. Taking power off the shaft increases input
power a similar amount. Both are true when you do both at once.
Thinking about this reminds me about my tube bending teacher, he had
a couple of these old motors in his shop (little ones, less than
1HP). According to him there where areas in NYC that received DC
instead of AC until after WW2 (not like I'm old enuf to know!)
Neon
--- End Message ---
--- Begin Message ---
Get a look at ours Renault rapid car in the http://evalbum.com trading post
so you will find easely one Sepex EV sized motor to buy.
Philippe
Et si le pot d'�chappement sortait au centre du volant ?
quel carburant choisiriez-vous ?
http://vehiculeselectriques.free.fr
----- Original Message -----
From: "Peter VanDerWal" <[EMAIL PROTECTED]>
To: "EV" <[EMAIL PROTECTED]>
Sent: Thursday, March 27, 2003 7:09 AM
Subject: Re: AC controllers
> Field weakening also reduces the efficiency of the motor and will result
> in less range.
> Also on series wound motors field weakening can lead to motor arcing
> which can damage the motor.
>
> It would be better to use a seperately excited motor, these are designed
> to have a different field current to the armature current. Of course
> finding EV size SepEx motors is a little tougher than finding series
> wound motors, but it is possible.
>
> On Wed, 2003-03-26 at 14:03, Mark Thomasson wrote:
> > Thanks for your time analyzing this. Under the circumstances you
mention
> > below, the best design would be the field weakening approach shown at
> > http://www.geocities.com/thomassonmj/motor_circuit.html . By using
field
> > weakening to control speed though most of the speed range, all the
batteries
> > will usually be in service. This adds some complexity, but it does give
> > continuous, stepless control through most of the speed range. For the
low
> > tech solution, field current could be controlled with a rheostat without
> > much loss in efficiency. I think fusing the circuit will protect it
from
> > contact welding. Thanks again, Mark T.
> >
> >
> > ----- Original Message -----
> > From: "Peter VanDerWal" <[EMAIL PROTECTED]>
> > To: "EV" <[EMAIL PROTECTED]>
> > Sent: Wednesday, March 26, 2003 12:11 AM
> > Subject: Re: AC controllers
> >
> >
> > > I was finally able to get into your site and see your diagram.
> > >
> > > Regardless of what you think your arrangement will definitely result
in
> > > an unballanced pack and reduced range.
> > > I spend about 1/2 the time driving around at 35 mph (that's the speed
> > > limit on most streets in my area). This means that the 12V and 24V
> > > sections of your pack would not be used during the constant speed
> > > portion of my trips (most of it).
> > > The other 1/2 the time I'm driving on the bypass at 55 mph, this uses
> > > the 48V section which is also used at 35 mph. This section will get
> > > drained long before the rest of the pack and will limit range.
> > > You are also subjecting portions of the pack to isolated high current
> > > draws which will cause Peukert to further reduce range.
> > >
> > > It is a clever idea and would be great for low power vehicles if it
> > > weren't for the possibility of shorting out the pack if a relay failed
> > > by welding shut (not uncommon).
> > >
> > > On Tue, 2003-03-25 at 15:23, Mark Thomasson wrote:
> > > > Thanks, lots of good background here. See my comments below. Mark
> > > > Thomasson
> > > >
> > > >
> > > > ----- Original Message -----
> > > > From: "Lee Hart" <[EMAIL PROTECTED]>
> > > > To: <[EMAIL PROTECTED]>
> > > > Sent: Monday, March 24, 2003 10:13 PM
> > > > Subject: Re: AC controllers
> > > >
> > > >
> > > > > Lee Hart wrote:
> > > > > >> The first problem is that you are not loading the batteries
> > equally.
> > > > >
> > > > > Mark Thomasson replied:
> > > > > > In actual city traffic conditions, all the batteries get used
almost
> > > > > > equally.
> > > > >
> > > > > That has not been my experience. For many years I drove a
ComutaVan,
> > > > > which has a 3-step 3-contactor controller (36v with resistor, 36v
> > > > > direct, and 72v direct). Its top speed was 55 mph (at 72v), but my
> > daily
> > > > > commute was on streets with a maximum 40 mph speed limit (which
only
> > > > > needed 36v). Thus, I only used 72v while accellerating or on
hills.
> > Most
> > > > > of the time was spent cruising at 36v.
> > > > >
> > > > > With your arrangement, I would have had half the range. I'd arrive
at
> > > > > work with the lower 36v half of the pack dead, but plenty of
charge
> > > > > still left in the upper 36v half.
> > > >
> > > > No, The method I am proposing does not work like this and does not
> > suffer
> > > > this problem, or at least not in the manner you describe.
Referring to
> > the
> > > > circuit shown at
> > http://www.geocities.com/thomassonmj/electric_drive.html ,
> > > > suppose that you have a 6v, 12v, 24v, and a 48v battery (represented
by
> > B1
> > > > to B4 in the circuit diagram). Also suppose your top speed is 60
MPH at
> > > > full voltage of 90v, and assume that speed is directly proportional
to
> > > > voltage. For the 15 available voltage steps, the table below shows
the
> > > > motor voltage, the speed, and the batteries used:
> > > >
> > > > step 1 6v 4 mph 6v
> > > > step 2 12v 8 mph 12v
> > > > step 3 18v 12 mph 6v 12v
> > > > step 4 24v 16 mph 24v
> > > > step 5 30v 20 mph 6v 24v
> > > > step 6 36v 24 mph 12v 24v
> > > > step 7 42v 28 mph 6v 12v 24v
> > > > step 8 48v 32 mph 48v
> > > > step 9 54v 36 mph 6v 48v
> > > > step10 60v 40 mph 12v 48v
> > > > step11 66v 44 mph 6v 12v 48v
> > > > step12 72v 48 mph 24v 48v
> > > > step13 78v 52 mph 6v 24v 48v
> > > > step14 84v 56 mph 12v 24v 48v
> > > > step 15 90v 60 mph 6v 12v 24v 48v
> > > >
> > > > If your usual speed is 40 mph (step10), you would be using
batteries12v
> > and
> > > > 48v. If you're on a hill or need to speed up some, you go to step
11
> > > > (batteries 6v, 12v, 48v) or step 12 (batteries 24v, 48v), or maybe
> > higher
> > > > with other battery combination. If you need to slow down, step 9
uses
> > > > batteries 6v and 48v. The point is that the batteries are
shuffled in
> > and
> > > > out of the circuit in a manner that tend to balance their loading
during
> > the
> > > > normal variations of driving speeds. However, if you spend most of
your
> > > > time below 32 mph, then, with this design, the 48 volt bank will be
> > under
> > > > utilized. For this and other reasons, the control scheme shown at
> > > > http://www.geocities.com/thomassonmj/motor_circuit.html has some
> > definite
> > > > advantages. Using a shunt field motor, the armature voltage steps
> > described
> > > > above control speed up to 20 mph. Then, with armature voltage at
> > maximum
> > > > and all batteries in service, field voltage is weakend to control
speed
> > up
> > > > to 60 mph. Since the field current of shunt motors is typically
only 5%
> > of
> > > > the armature current, controlling this current uses relatively
> > inexpensive
> > > > components. Also, speed control above 20 MPH is continuous with no
> > steps.
> > > > With this arrangement, you could think of the armature voltage
control
> > as a
> > > > soft starting system, with the field weaking as the main speed
control.
> > > > >
> > > > > >> Next problem; you still have a lot of contactors. The way they
are
> > > > > >> arranged, if one fails shorted, it could be disastrous to close
the
> > > > > >> next one.
> > > > >
> > > > > > Good point. Each battery bank should be fused.
> > > > >
> > > > > Note that a fuse is a resistor. It will have more voltage drop
than a
> > > > > contactor. They are also amazingly expensive for ones that is
> > guaranteed
> > > > > to work at high DC voltages and currents. You always need at least
> > some
> > > > > fuses, but want to minimize the number of them.
> > > > >
> > > > > I think a better solution is not to use SPST contactors; use SPDT
> > > > > contactors, built so it is physically impossible to close both
> > contacts
> > > > > at once even in the event of a welded contact. This is always done
in
> > > > > commercial contactor controllers.
> > > >
> > > > Unfortunately, this control scheme does not allow the use of SPDT
> > > > contactors. The interlocking you mention could be accomplished with
> > > > auxiliary contacts off each contactor tied back into the control
circiut
> > of
> > > > the appropriate interlocked contactor.
> > > >
> > > > >
> > > > > >> This problem has been studied for a very long time by some
great
> > > > > >> minds. You might want to look at some of their solutions.
> > > > >
> > > > > > Exactly, that's why I'm asking you guys for input!
> > > > >
> > > > > Most of the "guys" today have never even seen a contactor
controller.
> > > > > :-) So, you'll have to study old equipment, books, articles,
patents,
> > > > > etc. to see how they were done in their "golden age". Nowdays,
most of
> > > > > the engineers who knew how to design them are dead. So, the ones
you
> > see
> > > > > today are often naive designs by people who lack the knowledge and
> > > > > experience to do it right.
> > > > >
> > > > > Thus, it's easy to find a high-mileage 1920 Detroit Electric with
its
> > > > > original contactor controller that still works. And, it's easy to
find
> > a
> > > > > low-mileage CitiCar or golf cart with a contactor controller
that's
> > > > > destroyed.
> > > > >
> > > > > >> For example, the batteries can be switched in series-parallel
> > > > > >> combinations so the load is always divided equally between
them.
> > > > > >> Twelve 6v batteries can be wired for... 6v, 12v, 18v, 24v, 36v,
72v
> > > > >
> > > > > > This arrangement would take 33 contacts and gives only 6 steps.
> > > > >
> > > > > Correct; though that's 11 series/parallel contactors.
> > > >
> > > > Thanks, good catch.
> > > >
> > > > >
> > > > > > If you are willing to give up on the symmetry, you could get all
> > > > > > 12 evenly spaced steps.
> > > > >
> > > > > If you are using a PM motor, then you need more steps because its
> > speed
> > > > > is directly proportional to voltage. With a series motor (much
more
> > > > > common in EVs), you need fewer steps because motor speed is a
function
> > > > > of both voltage and load. With a series motor, roughly 2:1 voltage
> > steps
> > > > > turns out to be adequate (6v, 12v, 24v, 48v, 96v, ...)
> > > >
> > > > The new method gives you smooth 6v increments all the way up.
> > > >
> > > > >
> > > > > > The new method would give 15 steps with 15 6v batteries, but
only
> > > > > > use 9 relays. Balancing of battery discharge would depend on the
> > > > > > natural variability of driving speed.
> > > > >
> > > > > There was a streetcar controller similar to what you describe.
> > However,
> > > > > they had a scheme to balance the discharge. All the batteries were
in
> > > > > series. There were two *big* rotary switches, that could select
any
> > tap
> > > > > from 0v to full pack voltage in 1-battery steps. One wire of each
> > rotary
> > > > > switch went to each side of the motor.
> > > > >
> > > > > Start with both rotary switches fully counterclockwise, so both
motor
> > > > > leads were at the 0 volt tap. To accellerate, turn ONE of the
rotary
> > > > > switches up. 6v, 12v, 18v, 24v... the farther you advance it, the
> > faster
> > > > > you go.
> > > > >
> > > > > But, this would discharge the batteries at the lower end faster,
> > because
> > > > > they are used less. So, to slow down, leave the first switch where
it
> > > > > was, and move the SECOND switch up to meet it. This brings the
motor
> > > > > voltage back down. 24v, 18v, 12v, 6v, and 0v when both switches
are on
> > > > > the same tap. This discharges the batteries at the higher end of
the
> > > > > pack faster, thus compensating so all batteries average out to the
> > same
> > > > > discharge rate.
> > > > >
> > > > > There was a voltmeter between the two taps, so the operator could
see
> > > > > the battery voltage. It was a manual process; he looked at the
> > voltages
> > > > > to see where his weakest battery was, and avoided using that one.
> > > > >
> > > > > The rotary switches were big slate panels, with coin-sized
contacts
> > > > > arranged in a circle. The two switch arms were concentric cranks
that
> > > > > the operator controlled manually.
> > > > >
> > > > > >> The classic series-parallel switch is a single contactor with 3
> > > > > >> contacts:
> > > > > >> ______________________
> > > > > >> + __|__ K1b |
> > > > > >> battery 1 ___ normally closed / K1c
> > > > > >> |__________/___________| normally open
> > > > > >> | K1a __|__+
> > > > > >> / normally open ___ battery 2
> > > > > >> |______________________| -
> > > > > >>
> > > > > >> If you don't need to do regen (carry current in both
directions),
> > > > > >> then K1a and K1c can be replaced by a big diode. Then series-
> > > > > >> parallel switching is done with a single SPST contactor.
> > > > >
> > > > > > The new method also lets you reduce relay count by using diodes,
> > > > > > but diodes always have a forward biase voltage drop (~.7 v for
> > > > > > silicon) and therefore energy loss
> > > > >
> > > > > Contactors have a voltage drop too, especially as they age.
> > > >
> > > > Mine have .004 ohms each after light usage.
> > > >
> > > > >
> > > > > For low voltage systems you wouldn't use silicon diodes; you'd use
> > > > > Schottky diodes (0.5v drop), germanium diodes (0.25v drop), or
MOSFETs
> > > > > (even less)
> > > >
> > > > I wonder how the cost of these alternative device compare to
silicon?
> > > > .
> > > > >
> > > > > Diodes have other big advantages. They provide a path for the
> > inductive
> > > > > motor current during switching, which greatly reduces contact
arcing
> > to
> > > > > extend life.
> > > >
> > > > I planned to use a free wheeling diode, but after seeing very little
> > voltage
> > > > spiking across the relays on the oscilloscope, I left it out.
> > > >
> > > > >They also eliminate the timing problem between opening one
> > > > > contact and closing another "simultaneously".
> > > >
> > > > I originally used doides in the circuit for this purpose, but the
> > > > multiposition switch I use for speed control has enough "break
before
> > make"
> > > > that they were not needed and I left them out.
> > > >
> > > > >
> > > > > Peukert effects
> > > > >
> > > > > There's another factor you may not be aware of. The amphour
capacity
> > of
> > > > > a lead-acid battery depends on the load current. The higher the
> > current,
> > > > > the lower the capacity. It's called the "Peukert effect".
> > > > >
> > > > > Suppose you have golf cart batteries rated at 6v 225ah (at the
20-hour
> > > > > rate). If you load them at 75 amps, they only deliver 144
amphours. If
> > > > > you load them at 150 amps, they only deliver 122 amphours.
> > > > >
> > > > > Now suppose you have twelve of these batteries (a 72v pack). You
want
> > to
> > > > > cruise at a speed that requires 36v at 150 amps. With your
controller,
> > > > > only half the batteries are supplying this current. Each has to
> > provide
> > > > > 150 amps, so you can only drive for 122ah / 150a = 49 minutes.
> > > >
> > > > As discussed above, at half speed I have the 48v bank in service.
Speed
> > up
> > > > a little and I pick up the 6v bank also. Slow down a notch and the
48v
> > bank
> > > > drops out and the 6v, 12v, and 24v banks come into service. Small
> > > > variations in driving speed will balance out the discharge on the
banks.
> > > >
> > > > >
> > > > > With a series/parallel controller, the two halves of the pack
would be
> > > > > in parallel, so each battery delivers half the current or 75 amps.
Now
> > > > > you can drive for 144ah / 75a = 115 minutes. That's a big
> > difference --
> > > > > more than 2:1!
> > > >
> > > > It is definitely a good thing to have all the batteries in service
all
> > the
> > > > time, but this old method gives those big jumps in voltage and uses
more
> > > > hardware for much fewer voltage steps.
> > > > >
> > > > > With an electronic PWM controller, it would leave the pack wired
for
> > > > > 72v. It would draw 72v at 75 amps from the pack, but deliver 36v
at
> > 150
> > > > > amps to the motor. As for the series-parallel case, you could
drive
> > for
> > > > > 115 minutes.
> > > > >
> > > >
> > > > You lost me here. How did the PWM increase 75 A of input current to
150
> > A
> > > > of output current? Where did all those extra electrons come from?
> > > >
> > > >
> > > > > For your scheme to be viable in any but very small vehicles that
run
> > at
> > > > > full speed almost all the time, I think you really must have some
way
> > to
> > > > > equalize the loading on all the batteries.
> > > > > --
> > > > > Lee A. Hart Ring the bells that still can ring
> > > > > 814 8th Ave. N. Forget your perfect offering
> > > > > Sartell, MN 56377 USA There is a crack in everything
> > > > > leeahart_at_earthlink.net That's how the light gets in - Leonard
> > Cohen
> > > > >
> > > >
> > > --
> > > EVDL
> > >
> >
> --
> EVDL
>
--- End Message ---
--- Begin Message ---
Would there be a short buildup from the inductance in the battery loop and
the controller?
Just round off the corner a bit on the rising edge.
Andre' B. andre-at-usermail.com
If something cannot be defined, it does not exist.
Isaac Newton
-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]
Behalf Of Peter VanDerWal
Sent: Friday, March 28, 2003 2:54 PM
To: EV
Subject: Re: Buck converters, Correction.
On Fri, 2003-03-28 at 12:42, Otmar wrote:
> >When the switch turns on, the motors inductance initially fights the
> >flow of current but eventually (again microseconds here) current starts
> >flowing. When the voltage builds up to the desired level the switch
> >turns off.
>
> What is building up is current, not voltage. The voltage on the motor
> is a square wave with a high of the full battery voltage and a low of
> zero (actually -1V due to the diode drop in the freewheel path)
Oops, there I go confusing reality with what I read with a volt meter.
Otmar is (as usual) correct.
Perhaps I should have said "Apparent" voltage measured with a
voltmeter? Naw, Otmar said it better.
But, just for those of you who don't have am O-scope, if you measure
this with a Voltmeter(set for DC voltage) you will see a voltage that is
roughly equal to the time-averaged voltage of this square wave.
Just goes to show you that even Geniuses like me can screw up
occasionally ;-)
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--- Begin Message ---
When it comes to plugs and outlets, Europe has really does it a lot better.
Andre' B. andre-at-usermail.com
If something cannot be defined, it does not exist.
Isaac Newton
-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]
Behalf Of Grannes, Dean
Sent: Friday, March 28, 2003 11:59 AM
To: [EMAIL PROTECTED]
Subject: RE: Outlets (was That time of the year again...)
Lee makes a good point:
> The electric code says nothing about quality. The made-in-Mexico
> builder's special $0.29 outlets meet code. They are still junk. You
get
> what you pay for.
After a year of charging my Rabbit in the garage from the same 120V
outlet, I noticed sparks when I plugged into the wall outlet. I shut
off the breaker, then pulled the outlet. It was a "builder's special
$0.29" outlet (which I admit I installed) and had started to melt and
char from the daily prolonged high currents (10-12A) running through it.
It could have started a fire with another few uses. Fortunately, I
caught it in time and replaced the outlet and started using a different
outlet.
Now I have a beefy extension cord permanently plugged into a different
outlet (with a timer), and I plug into the extension cord. This reduces
strain on the outlet from repeated insertions (which also may have
contributed to the other outlet's demise).
The moral of the story is that if you have an outlet that you use every
day for prolonged charging near the rated limit of the outlet, unless
you know it's a beefy well-built outlet, it would be prudent to pull off
the faceplate (after cutting the power, of course) and visually inspect
the outlet every so often (yearly?). Or consider replacing it with a
heavy-duty outlet.
Dean
* LP8.2: HTML/Attachments detected, removed from message *
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--- Begin Message ---
Hi!
I mounted my MagneCharger (Edison EV one) otuside on a pole. I have a
serious question though:
How do I know if it's rated for outdoor use? As normal, there is nothing on
the box to say one way or another and although the fans at the bottom are
covered by a grate, it just doesn't feel waterproof. However the wires
coming out of it are in waterproof jackets.
Thoughts? I'm going to leave a tarp over it for now, but I don't want to
build a mini-shed if I can help it.
Chris
--- End Message ---
--- Begin Message ---
Hi Peter,
You got the bit where power is applied and the steel is not attracted to the
coil, wrong, the steel is attracted to the coil when power is applied, just
as the magnet is either pulled to it or pushed from it.
I mean it wouldn't work if it had no magnetic field, but if it had no
counter magnetic field there wouldn't be any Lenz.
And my actual test for this was to remove power after the motor was
accelerated to 2000 rpm and measure voltage out both directly from the coils
and from a fwbr across the coils.
I got it down to 2 volts on a 24 volt motor and by your own admission of
back emf equaling input minus losses the amount of energy in this motor
going to the shaft as work must surely be more than if the voltage reading
was 20 volts when it spins down.
I further stated that 18 volts had been measured before the motor was
rewired to this configuration.
The people trying to rip everyone off with OU and FE claims often revert to
personal insults when someone comes along and points out that that they are
wrong and it seems to me you too are busy "attacking" me instead of proving
my science wrong.
All im suggesting here is there might be a way to get more of what you put
in, out, as shaft output and surely that is worth thinking about.
Garry Stanley
Cable.net.nz
--- End Message ---
--- Begin Message ---
I would recommend calling the Edison EV Tech Center in Pomona to find
out for sure. Please ask for either Naum Pinsky (Mgr., EV Battery
Testing and Evaluation 626-302-3983) OR Loic Gaillac (Engineer
909-469-0270). If neither are available, you could probably ask for
anyone in the tech center -- they would certainly have the right answers
for you.
Melanie Savage
Vice President, Communications & Operations
Advanced Zinc Energy Systems
2400 Lincoln Avenue
Suite 157
Altadena, CA 91001
(626) 296-6453-phone
(626) 296-6311-fax
Finding strategic markets and applications for advanced technology
-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On
Behalf Of Christopher Zach
Sent: Friday, March 28, 2003 1:42 PM
To: [EMAIL PROTECTED]
Subject: MagneChargers outdoors
Hi!
I mounted my MagneCharger (Edison EV one) otuside on a pole. I have a
serious question though:
How do I know if it's rated for outdoor use? As normal, there is nothing
on
the box to say one way or another and although the fans at the bottom
are
covered by a grate, it just doesn't feel waterproof. However the wires
coming out of it are in waterproof jackets.
Thoughts? I'm going to leave a tarp over it for now, but I don't want to
build a mini-shed if I can help it.
Chris
--- End Message ---
--- Begin Message ---
A friend of mine would like to have an Insight conversion. His EV1 is gone
the Segway is comming and not to put it down but he feels it might not meet
his needs. With the Insight one of the most efficient bodys out there it
seems a natural for conversion. I figure a conversion with second from the
top line Zilla controller an 8" ADC all the things you need to make it work,
NiZn batteries and 5k for the person or persons converting it and the car
itself would cost around 20k. Am I in the right ballpark? Lawrence
Rhodes......
--- End Message ---
--- Begin Message ---
on 3/28/03 2:10 PM, Lawrence Rhodes at [EMAIL PROTECTED] wrote:
> A friend of mine would like to have an Insight conversion. His EV1 is gone
> the Segway is comming and not to put it down but he feels it might not meet
> his needs. With the Insight one of the most efficient bodys out there it
> seems a natural for conversion. I figure a conversion with second from the
> top line Zilla controller an 8" ADC all the things you need to make it work,
> NiZn batteries and 5k for the person or persons converting it and the car
> itself would cost around 20k. Am I in the right ballpark? Lawrence
> Rhodes......
>
Rhodes, Hertz still has the Think EV for rent in the city. It is only $250
a month. It would be a good thing to try out and see if he or she liked it.
$250 a month is a great deal. Unfortunatly they will only be around until
Aug. or Sept. Then they'll be taken out of their fleet and shipped back.
Good luck
Horn player in Sacramento
Carmine
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