EV Digest 4183
Topics covered in this issue include:
1) Aviation NiCad maintenance book
by Eric Poulsen <[EMAIL PROTECTED]>
2) Re: Warning sound for approaching EV
by David Dymaxion <[EMAIL PROTECTED]>
3) Advice on electric scooter sought
by Mark Dodrill <[EMAIL PROTECTED]>
4) Re: dc-dc converter,5-40V, 5A control
by Rod Hower <[EMAIL PROTECTED]>
5) Re: Tires again - tire width
by Evan Tuer <[EMAIL PROTECTED]>
6) Re: Electravan cord & safety switch problem.
by Mike Chancey <[EMAIL PROTECTED]>
7) Canadian EV parts designer
by [EMAIL PROTECTED]
8) Re: RoboMower
by Evan Tuer <[EMAIL PROTECTED]>
9) Re: Tires again - tire width
by "Patrick Maston" <[EMAIL PROTECTED]>
10) Re: Motor Break in
by "STEVE CLUNN" <[EMAIL PROTECTED]>
11) Re: Retail Value of 2001 Gem Utility?
by "J Mac" <[EMAIL PROTECTED]>
12) Flooded motor
by "M.G." <[EMAIL PROTECTED]>
13) RE: Canadian EV parts designer
by "Bill Dennis" <[EMAIL PROTECTED]>
14) Re: Post disaster
by "Lawrence Rhodes" <[EMAIL PROTECTED]>
15) Re: dc-dc converter,5-40V, 5A control
by Martin K <[EMAIL PROTECTED]>
16) Re: RoboMower
by Derrick J Brashear <[EMAIL PROTECTED]>
17) EV parts on eBay
by [EMAIL PROTECTED]
18) Re: motor cooling
by brian baumel <[EMAIL PROTECTED]>
19) RE: BB-600 Nicad Cells - shipping
by "Bill" <[EMAIL PROTECTED]>
20) re: motor cooling
by "Marc Michon" <[EMAIL PROTECTED]>
21) RE: Regenerating a series wound motor
by "djsharpe" <[EMAIL PROTECTED]>
22) Stories on EV1 Vigil
by Marc Geller <[EMAIL PROTECTED]>
23) RE: Regenerating a series wound motor
by "djsharpe" <[EMAIL PROTECTED]>
24) Re: Flooded motor
by James Massey <[EMAIL PROTECTED]>
25) RE: Regenerating a series wound motor
by James Massey <[EMAIL PROTECTED]>
--- Begin Message ---
"A short but in-depth guide from Jeppesen to construction,
installation, and servicing of lead-acid and nickel-cadmium aircraft
batteries."
http://www.amtbooks.com/aircraft_batteries.htm
--- End Message ---
--- Begin Message ---
Big problem, how do you keep your kilt from flying open when cruising
at highway speeds?
--- Michael Shipway <[EMAIL PROTECTED]> wrote:
> I've been considering bag-pipe music for my motorcycle, tempo keyed
> to
> motor speed of course.
> I've found that a bag-pipe tape in my car's stock 10 watt stereo
> will
> cut thru the noise of the loudest, thumpiest boom-boom cars in my
> area,
> and make the thumper's driver turn and look.
>
> Besides, the bike looks funny without exhaust pipes, so I was
> thinking
> of hanging a bundle of chanters in it's place.
> original real picture here for comparison:
> http://www.generalist.org/madmike/April2002/BikeLeftComplete1.jpg
>
> See the edited (Bag-pipified) image here:
>
http://www.generalist.org/madmike/April2002/BikeLeftComplete1wBagPipes.jpg
>
>
> "Mad" Mike Shipway
>
> Ivo Jara wrote:
__________________________________
Do you Yahoo!?
Yahoo! Small Business - Try our new resources site!
http://smallbusiness.yahoo.com/resources/
--- End Message ---
--- Begin Message ---
Hello all. It's been so unseasonable warm and sunny here in Seattle this
year, I've been thinking using an electric scooter to get to and from
work, instead of my car. A full electric car just isn't in the cards
for me now, but I did get a tax refund that might work.
I'm looking for an electric scooter that meets the following
requirments:
* It's a 11 mile (~18 km) commute one-way, so I'm sure I would
need to charge at work.
* Total elevation change is about 200 feet from start to finish,
with about a 250 max elevation gain in the middle.
* Max speed required is 40 mph for about 1 mile
* Other times speed is between 25 and 35 mph
* Some rolling hills but I can avoid any steep up/downgrades
* Full enclosure not required since I plan to ride only when
it is relatively nice
* Either homegrown or production would work
* Efficiency is more important than looks
* Needs to haul 200 lbs of people and stuff
* Don't care about battery weight, size, or chemistry, as long as it works
* Needs to have a seat
* Probably need at least a 750 watt motor
* Probably a 36 or 48 volt system
* Price of around $1500 US
* Ability to pull out the battery pack for charging is a plus
(even if it is 70+ lbs)
Does anyone have a suggestion on what I could use here to meet these
requirements, or modify something existing to meet them?
Ebay has a couple of interesting items: 7140833081,7141765328.
Also, if anyone knows of licensing/insurance issues related to scooters,
I'd appreciate that as well.
All feedback/thoughts appreciated.
Thanks.
Mark
--- End Message ---
--- Begin Message ---
"I myself am looking for a cheap way of making 5 - 48V
(adjustable) max. 5A out of 36V. Anybody have an idea?
(Its to control the field on my 36V elec-trak
compound wound motor)
Markus",
I just wrote software for my 20A 3-phase BLDC drive
that allows it to run a series motor h-bridge style or
just regular
single direction series or PM up to 60A by puting the
the FETS in parallel.
You could put your shunt field in the H-bridge
configuration and have reversing capability.
It will go up to 20 amps in this mode, but I think the
ET field will draw less than 5A (more like 3 on my
E-15 I think).
Anyhow, this control is 3.5x3.5x2.5" and goes up to 63
Volts.
There's a schematic for all of the different
configurations for a 3-phase control.
http://groups.yahoo.com/group/osmc/files/Multimotor/
Rod
--- End Message ---
--- Begin Message ---
On Mon, 14 Mar 2005 07:06:02 -0500, Philip Marino
<[EMAIL PROTECTED]> wrote:
> Why do you want to change to narrower tires?
>
> For the same tire pressure and tire construction, the rolling resistance
> will be less for a wider tire. (because the deflection will be less)
>
> The reasons bicycle tires are very narrow have more to do with weight and
> air drag than rolling resistance. Also, narrow bike tires can be made to
> handle higher pressure more easily ( the tire stresses are lower for a given
> pressure if the tire is narrower) so that narrower tires can indirectly
> result in lower rolling resistance by allowing higher pressure. Also,
> because the stresses within a narrower tire are lower, that allows for
> thinner, more flexible sidewalls; that can also result in lower rolling
> resistance.
>
> But these benefits doesn't apply to car tires - narrower tires don't allow
> for higher pressures ( and, I don't believe, thinner sidewalls) Also, I
> don't think the weight difference would be significant in a car.
The width is significant in reducing drag though, even on cars. And,
if you are using the correct pressure for the load on your existing
tyres, you will be able to increase the pressure when you go to
narrower tyres, thus keeping the deflection the same and running them
closer to their maximum rating.
The weight saving probably is insignificant on a car though, as you say.
Overall I think there should be a reduction, or I hope so anyway :)
--- End Message ---
--- Begin Message ---
Lawrence Rhodes wrote:
Bad design. There is a nut holding the switch in the center of the four
charging contacts. It unscrewed welding to the contact point of the 12v
system. The truck runs but I can't get 12v out of the receptical.
Something blew. Also the switch has two wires to one contact. The only
thing I can think of is it is supposed to disable the 12v system without
which the truck goes no where. It must somehow make continuity to ground.
LR........
Not bad design, really really bad design. I sold my Jet 007 years ago, so
I am working from memory here, so correct me if I am wrong. The receptacle
on the EV is four prong male, the connector on the charger output is four
prong female. The switch is a long stem single pole normally closed switch
mounted in the center of the EV receptacle in place of a center
contact. Unplugging the cord completes a circuit allowing the main
contactor to close. When these switches failed, most were bypassed or
removed.
Now, what is wrong with this picture. Well we have four male prongs
sticking out of the receptacle that are always live. Two are pack positive
and negative, two are 12 volt positive and negative. Either way, a
disaster waiting to happen. Just add water or fingers or.... The charger
output end is female, which makes sense until you realize the charger won't
power up without first being connected to the batteries.
The charger output should be male, the EV inlet should be female. Yes,
this is just the reverse of normal EVs, but remember you are feeding DC out
of a charger not AC into one. On my Jet I replaced the defective
connectors with a four prong roto-loc 30 amp female receptacle on the car
and a matching male plug for the charger. In my case I gave up the "no
drive off" protection. For you I would suggest using a 5 prong connector
pair, with the extra pin jumpered to the 12 volt negative pin on the
charger side. On the EV side, feed that lead to one side of the coil on a
12 volt relay. Feed the other side of the coil from the "ignition"
hot. Wire the normally closed contacts on the relay to complete the 12
volt circuit originally wired to the receptacle switch. Now, when the cord
is plugged in and the ignition is turned on, the relay will energize, open
the 12 volt feed to the main contactor, and prevents the EV from being
driven. Removing the plug cuts power to the relay and permits the main
contactor to close allowing the EV to operate.
FWIW, I understand the original plugs and receptacles were a custom order
item made especially for the Jets.
Thanks,
Mike Chancey,
'88 Civic EV
'95 Solectria Force
Kansas City, Missouri
EV List Photo Album at: http://evalbum.com
My Electric Car at: http://www.geocities.com/electric_honda
Mid-America EAA chapter at: http://maeaa.org
Join the EV List at: http://www.madkatz.com/ev/evlist.html
--- End Message ---
--- Begin Message ---
Has anyone dealt with products from ElectroCraft Systems:
http://home.interlog.com/~dgv/
Looks promising...
--- End Message ---
--- Begin Message ---
On Sun, 13 Mar 2005 22:12:46 -0800, Dave <[EMAIL PROTECTED]> wrote:
> I will do that. I am wondering if there is a short in the batteries. When I
> attach the charger, it starts to fire up, but immediately shuts off, then
> tries again. The batteries are in a case, and I will have to find a way to
> open it to access the leads.
That's a possibility, it's also possible that the batteries have been
sitting for a long time and immediately go to a high voltage when put
on charge, and the charger logic shuts off. In that case they are
probably useless but you could try charging them individually for a
few hours with an automotive charger. If the robot's charger then
stays on, do a few full charge / discharge cycles and you might get a
bit more use out of them.
A simple multimeter set to the voltage will help you find out what's
going on if you can get access to the battery terminals.
32V for the power supply is not unreasonable if there is some sort of
charge controller circuit between the transformer and the batteries.
--- End Message ---
--- Begin Message ---
In Bob Brant's book, Build Your Own Electric Vehicle, he says to use the
largest diameter wheels with tires that are thin in cross section (175
is better than 185) and low in aspect ratio (50% is better than 60%,
etc.) that you can get away with, like a motorcycle wheel/tire combo.
This will give the lowest rolling resistance.
Patrick
>>> [EMAIL PROTECTED] 3/14/05 6:30:53 AM >>>
On Mon, 14 Mar 2005 07:06:02 -0500, Philip Marino
<[EMAIL PROTECTED]> wrote:
> Why do you want to change to narrower tires?
>
> For the same tire pressure and tire construction, the rolling
resistance
> will be less for a wider tire. (because the deflection will be
less)
>
> The reasons bicycle tires are very narrow have more to do with weight
and
> air drag than rolling resistance. Also, narrow bike tires can be
made to
> handle higher pressure more easily ( the tire stresses are lower for
a given
> pressure if the tire is narrower) so that narrower tires can
indirectly
> result in lower rolling resistance by allowing higher pressure.
Also,
> because the stresses within a narrower tire are lower, that allows
for
> thinner, more flexible sidewalls; that can also result in lower
rolling
> resistance.
>
> But these benefits doesn't apply to car tires - narrower tires don't
allow
> for higher pressures ( and, I don't believe, thinner sidewalls)
Also, I
> don't think the weight difference would be significant in a car.
The width is significant in reducing drag though, even on cars. And,
if you are using the correct pressure for the load on your existing
tyres, you will be able to increase the pressure when you go to
narrower tyres, thus keeping the deflection the same and running them
closer to their maximum rating.
The weight saving probably is insignificant on a car though, as you
say.
Overall I think there should be a reduction, or I hope so anyway :)
--- End Message ---
--- Begin Message ---
----- Original Message -----
From: "Jeff Shanab" <[EMAIL PROTECTED]>
To: "Electric Vehicle Discussion List" <ev@listproc.sjsu.edu>
Sent: Sunday, March 13, 2005 9:30 PM
Subject: Motor Break in
I heard I am suppose to break in the brushes on a new motor. Are the
brushes already seated in on the warp 9 ?
I don't think so , if its shine copper then no . there will be a dark brown
coating on the com when they are ,
I connect up a 12v battery for 1/2 hour but saw no change on the com and
no sparks.
I have been doing a little braking in of the motor and batteries at the same
time . I put somthing to hold the pot box open a little and let the motor
spin , on 240 v 10 battery amps or less seems to spin the motor pretty fast
,
The motor is now connected to the tranny!(wahoo) When connected to the
same battery it definitly pulls more amps and slows down after only a few
moments, but disconnected I can turn the aux shaft as easy as when it
wasn't connected to tranny and clutch. It is an SLI battery and is
probably in need of chargeing.
the 9" will pull around 50 amps with no load
Is 12volts a laughabley low voltage for this?
I drove the kit car around the block on 12v
It was very difficult to get the tranny shaft into the clutch and I am
hopeing It doesn't have to come apart. If break in is needed, can it be
done while driving?
yes , just drive easy ,
steve clunn
--
No virus found in this outgoing message.
Checked by AVG Anti-Virus.
Version: 7.0.308 / Virus Database: 266.7.2 - Release Date: 3/11/2005
--- End Message ---
--- Begin Message ---
Is this GEM capable of of being upgraded with a stronger motor &
more/different batteries to get higher miles per charge?
Thanks .. Mac
From: "Lawrence Rhodes" <[EMAIL PROTECTED]>
Reply-To: ev@listproc.sjsu.edu
To: "J Mac" <[EMAIL PROTECTED]>, <ev@listproc.sjsu.edu>
Subject: Re: Retail Value of 2001 Gem Utility?
Date: Sun, 13 Mar 2005 23:10:42 -0800
2k to 3.5k. Good luck. LR............
----- Original Message ----- From: "J Mac" <[EMAIL PROTECTED]>
To: <ev@listproc.sjsu.edu>
Sent: Sunday, March 13, 2005 7:02 PM
Subject: Retail Value of 2001 Gem Utility?
What is a good range to consider for buying:
2001 GEM Utility
(don't yet know if it's the short bed or long bed)
2 Passenger
Rear plexi-glass window
Staked Bed
Locking truck toolbox
100 miles
Are there any online resources for this (blue book type of info)?
Thanks,
Mac
_________________________________________________________________
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--- End Message ---
--- Begin Message ---
Great news I just found out that a newer fork truck is being scrapped at
work and I get to gut it for all of it's electrical components.
Now the bad news the truck was in a flood and everything is muddy and rusty.
I'm not to worried about the mud but the rust concerns me I want to try
to use this motor in my first conversion.
I will take the motor apart and replace the bearings and clean it as
best possible.
My question is it possible to check the armature for damage "shorted
windings" with a growler used for checking starter motors? The armature
I am talking about is pretty large it is from an 11 inch traction motor.
Any suggestions are appreciated.
My EV Grin is coming soon :)
Mike G.
--- End Message ---
--- Begin Message ---
Search back in the archives a month or two. I asked the same question about
them. Seems that some people like them and some have had problems.
Bill Dennis
-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On
Behalf Of [EMAIL PROTECTED]
Sent: Monday, March 14, 2005 5:13 PM
To: EV Discussion List
Subject: Canadian EV parts designer
Has anyone dealt with products from ElectroCraft Systems:
http://home.interlog.com/~dgv/
Looks promising...
--- End Message ---
--- Begin Message ---
I took my damaged battery to American Battery in Hayward and Jim fixed it
for free. Took 10 minutes. Turns out U.S. Battery has a better post alloy
than Trojan. He used a tourch and some bar lead and in two passes it was
fixed. Looks like new. LR..............
----- Original Message -----
From: "Electro Automotive" <[EMAIL PROTECTED]>
To: <ev@listproc.sjsu.edu>
Sent: Monday, March 14, 2005 9:47 AM
Subject: Re: Post disaster
At 03:50 PM 3/12/05 -0800, you wrote:
Had a recent melt down at work.
Golf cart repair tech came out and drilled a small hole in the left overs
of a melted post. Then drove a self tapping screw with a replacement lug
on it. Melt down occurred due to loose cable which became over heated
during charging.
Yes. This is why you don't want to use lugs bolted to the top of univeral
posts in a road-going EV. They WILL become loose, as the lead deforms
under pressure and the stud creeps up and out of the post. They WILL
melt, with great regularity.
Shari Prange
Electro Automotive POB 1113 Felton CA 95018-1113 Telephone 831-429-1989
http://www.electroauto.com [EMAIL PROTECTED]
Electric Car Conversion Kits * Components * Books * Videos * Since 1979
--- End Message ---
--- Begin Message ---
"I myself am looking for a cheap way of making 5 - 48V
(adjustable) max. 5A out of 36V. Anybody have an idea?
(Its to control the field on my 36V elec-trak
compound wound motor)
Markus",
Hi Markus,
You could make a low-side buck switching regulator very easily out of a
controller chip like the UC3843.
If you want a high-side switch (a lot of people prefer it for higher
voltage apps) you could combine a chip like that with a boot-strap
converter made out of a couple transistors and diodes.
If you don't know anything about electronics, sorry I recommended this :)
--
Martin K
http://wwia.org/sgroup/biofuel/
--- End Message ---
--- Begin Message ---
On Mon, 14 Mar 2005, Evan Tuer wrote:
On Sun, 13 Mar 2005 22:12:46 -0800, Dave <[EMAIL PROTECTED]> wrote:
I will do that. I am wondering if there is a short in the batteries. When I
attach the charger, it starts to fire up, but immediately shuts off, then
tries again. The batteries are in a case, and I will have to find a way to
open it to access the leads.
That's a possibility, it's also possible that the batteries have been
sitting for a long time and immediately go to a high voltage when put
on charge, and the charger logic shuts off. In that case they are
probably useless but you could try charging them individually for a
few hours with an automotive charger. If the robot's charger then
stays on, do a few full charge / discharge cycles and you might get a
bit more use out of them.
Actually, thinking more, I saw this after my robomower was unplugged for
all of last winter.
I let it be for a while and then unplugged it. Then I came back and put
the charger plug back in, walked away, and it charged again.
--- End Message ---
--- Begin Message ---
Anyone need a 300Vdc to 15Vdc converter?
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=73128&item=7500632618
--- End Message ---
--- Begin Message ---
I have (2) 240 CFM blowers mounted to the front of the
car. I'm guessing that would be more than enough.
they'll spin up for low speed/high current and at
higher speeds I'll let the air flow take care of it...
so it is suggested to put an air filter inline with
each blower? how fine of a filter would people
suggest? typical auto filter or something that'll
allow more air flow?
--- Lee Hart <[EMAIL PROTECTED]> wrote:
> brian baumel wrote:
> > Could some one tell me if this is a bad idea. I am
> > working on piping air into my motor for cooling.
> The
> > current plan is to scoop the air from the front of
> the
> > car and pipe it to the back where the motor is.
>
> The air passages through the motor are pretty small
> and tortuous. Ram
> air alone will not provide enough pressure to move
> any useful amount of
> air. So, you need a squirrel-cage blower to develop
> enough pressure to
> move useful amounts of air.
>
> Once you have a blower, it does not really matter
> where it gets its air
> intake. It would be better to place the intake
> somewhere that it won't
> pick up dust, snow, or other debris.
> --
> Ring the bells that you can ring
> Forget your perfect offering
> There is a crack in everything
> That's how the light gets in
> -- Leonard Cohen, from "Anthem"
> --
> Lee A. Hart 814 8th Ave N Sartell MN 56377
> leeahart_at_earthlink.net
>
>
__________________________________
Do you Yahoo!?
Yahoo! Mail - You care about security. So do we.
http://promotions.yahoo.com/new_mail
--- End Message ---
--- Begin Message ---
Thanks for the update
Bill
-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On
Behalf Of Tim Humphrey
Sent: Monday, March 14, 2005 6:56 AM
To: ev@listproc.sjsu.edu
Subject: BB-600 Nicad Cells - shipping
I know all you guys that bought these cells want them yesterday :-))
Please bear with me.
I got a great deal from a friend of my father-in-law's, (he used to
drive
for him).
His shipping rate to get the cells to me are 75% of the next lowest
quote
I received. PLUS he will unload the pallets into his warehouse and let
me
re-package them in his warehouse for forwarding out west. He will then
truck them to the western destinations for us. (kind of a one stop shop
for shipping).
I will let the group(s) know in an off-list e-mail what his cost will be
to ship them and then the individual groups can say yes or no to use his
offer. (but, I don't think it can be beat).
In the meantime, I have quite a few people waiting to see if any more
cell's are available. I won't know until the shipment arrives and I can
get a real count as to how many there are.
--
Stay Charged!
Hump
"Whether you think you can or think you can't, you are right!" --Henry
Ford
--- End Message ---
--- Begin Message ---
i was reading about Uc Davis they have some good battery cooling systems
they pull the air off the cowl in front of the windshield
and most cars have vents there
a high pressure area, they also have a connectiion to the AC
look up http://www.team-fate.net/
Marco fresno ,CA where the Sierra Nevada mountains are hidden (smog)
>brian baumel wrote:
> Could some one tell me if this is a bad idea. I am
> working on piping air into my motor for cooling. The
> current plan is to scoop the air from the front of the
> car and pipe it to the back where the motor is.
>The air passages through the motor are pretty small and tortuous. Ram
>air alone will not provide enough pressure to move any useful amount of
>air. So, you need a squirrel-cage blower to develop enough pressure to
>move useful amounts of air.
>Once you have a blower, it does not really matter where it gets its air
>intake. It would be better to place the intake somewhere that it won't
>pick up dust, snow, or other debris.
--
>Lee Hart
--- End Message ---
--- Begin Message ---
Further to discussions with Lee:
I have been driving my converted Daihatsu and agonising over the
electrical braking situation at every traffic light. A solution that
might be feasible is to hit the field winding with current in the
opposite direction to motoring using two CTs (current transformer)with
half bridge rectifiers. The high voltage side could be fed with a
converter but I will not deal with this at the moment. There is no need
to alter any topography to accommodate this.
How this would work is that you have some additional control that cannot
be activated unless you have a foot on the brake pedal first. The
control could be on the gear shift or another pedal next to the accel
pedal etc.
What happens is that you hit the field with more current than the
current being supplied to the battery. Perhaps this will be stable
enough with an appropriate control system to slow you. As speed reduces,
field Amps increases which is what you want. There should be a path
around the controller with existing diodes. I have not heard of this
idea before. It could be called a differential braking system for series
wound motors.
The braking current would be much less than a direct current injection
and should lessen the flux distortion/neutral axis issue.
Is there a flaw in my logic?
David Sharpe
-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On
Behalf Of Lee Hart
Sent: Sunday, 27 February 2005 9:10 AM
To: ev@listproc.sjsu.edu
Subject: Re: Regenerating a series wound motor
djsharpe wrote:
> I am assuming any proposal would add inductance & resistance to
> replace the motor armature during the regenerating phase.
No; this is not (normally) necessary.
A PWM controller is more properly called a "buck converter". It requires
4 parts to function efficiently; 1 switch, 1 diode, 1 capacitor, and 1
inductor. The switch is usually a transistor; bipolar, MOSFET, or IGBT.
The diode is usually silicon or schottky. They sometimes "cheat" on the
capacitor and use the battery to provide some or all of the capacitance.
They also "cheat" on the inductor and use the motor's inherent
inductance when possible. Sometimes multiple devices are used in
parallel to save money.
A series motor has a lot of inductance, mainly provided by the field.
So, a separate inductor is rarely used with series motors. You *will*
sometime see separate inductors with PM or shunt motors to get them to
work right.
Any normal controller would have no trouble driving just the field of a
series motor. The only problem would be if you have a *really* large
series motor (like an Advanced DC 9") and a really small controller
(like a Curtis 1221B). This motor is known to have insufficient
inductance for this controller even wired normally (field and armature
in series), so using the 1221B to drive just the ADC 9" field would make
a bad situation worse.
Ok; so you can drive just the field. What happens next?
You are running the series motor as a "separately excited" motor. This
means a) Varmature = K x Speed x Ifield (where K is a constant for the
given motor). So yes; you could use the controller to run enough field
current so the armature voltage is greater than the pack voltage at any
given rpm.
But, there are problems. Series motors assume that field current =
armature current. The magnetic fields produced by the armature and field
windings "warp" each other. When the current in both are the same, each
is strong enough to "fight off" the other. But if you weaken the field,
the armature current will "warp" the field. The apparent position of the
field moves from its real position. This shifts the optimum position of
the brushes for minimum arcing. Thus, reducing the field current
compared to the armature current increases arcing.
So, this scheme has a problem at high motor rpm. The equation requires
low field current to get Varmature = Vpack. But then you can only allow
low armature current; thus low regen current.
As the vehicle slows down, you need to increase Ifield to increase
Varmature so it still matches Vpack. So, you can have more armature
current, i.e. more regen current. In other words, you get the least
regen at the highest speed, and the most at low speeds -- backwards of
what you normally want.
The standard method to avoid this situation is to keep the field and
armature in series, and rewire the PWM controller as a "boost
converter". A boost converter momentarily shorts the motor; this causes
a rapid buildup of current (but not voltage). Then it connects the motor
to the battery. A pulse of current flows into the battery. Then the
motor is shorted, and the process repeats. Because of field inductance,
the actual current ramps up 10-20% when the motor is shorted, and back
down 10-20% when connected to the battery.
The problem with this setup is that the motor armature is operating at
high current and low voltage during regen. This is a much less efficient
operating point for series motors. Also, you need to reverse the field
to get this kind of generator action. This requires a reversing
contactor. Finally, the brush position for minimal arcing changes
between forward and reverse; thus the brushes are in the WRONG position
during regen; when current is high and arcing is the worst.
The fix for *this* problem is to add compensating windings to the motor.
These are typically interpoles and/or pole face windings; smaller field
windings connected in series with the armature and positioned so they
counteract the effect of the armature current on the field. The drawback
of these windings is that they add cost and take up space (the motor
gets bigger, heavier, and costs more).
--
Ring the bells that you can ring
Forget your perfect offering
There is a crack in everything
That's how the light gets in
-- Leonard Cohen, from "Anthem"
--
Lee A. Hart 814 8th Ave N Sartell MN 56377 leeahart_at_earthlink.net
--- End Message ---
--- Begin Message ---
Lots of newspapers are carrying the story of the arrests at the EV1
vigil, including Washington Post's 2nd story.
Quick, short letters to the editor couldn't hurt to keep the story in
the press.
http://www.washingtonpost.com/wp-dyn/articles/A35367-2005Mar14.html
http://www.sfgate.com/cgi-bin/article.cgi?file=/news/archive/2005/03/
14/state/n184509S79.DTL
http://www.sanluisobispo.com/mld/sanluisobispo/news/politics/
11136194.htm
http://www.montereyherald.com/mld/montereyherald/news/politics/
11136194.htm
http://www.mercurynews.com/mld/mercurynews/news/local/states/
california/northern_california/11136194.htm
http://www2.cbs5.com/topstories/local_story_072220231.html
--- End Message ---
--- Begin Message ---
Correction to my own posting. Added SAME instead of opposite
-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On
Behalf Of djsharpe
Sent: Tuesday, 15 March 2005 6:11 PM
To: ev@listproc.sjsu.edu
Subject: RE: Regenerating a series wound motor
Further to discussions with Lee:
I have been driving my converted Daihatsu and agonising over the
electrical braking situation at every traffic light. A solution that
might be feasible is to hit the field winding with current in the
SAME direction to motoring using two CTs (current transformer)with
half bridge rectifiers. The high voltage side could be fed with a
converter but I will not deal with this at the moment. There is no need
to alter any topography to accommodate this.
How this would work is that you have some additional control that cannot
be activated unless you have a foot on the brake pedal first. The
control could be on the gear shift or another pedal next to the accel
pedal etc.
What happens is that you hit the field with more current than the
current being supplied to the battery. Perhaps this will be stable
enough with an appropriate control system to slow you. As speed reduces,
field Amps increases which is what you want. There should be a path
around the controller with existing diodes. I have not heard of this
idea before. It could be called a differential braking system for series
wound motors.
The braking current would be much less than a direct current injection
and should lessen the flux distortion/neutral axis issue.
Is there a flaw in my logic?
David Sharpe
-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On
Behalf Of Lee Hart
Sent: Sunday, 27 February 2005 9:10 AM
To: ev@listproc.sjsu.edu
Subject: Re: Regenerating a series wound motor
djsharpe wrote:
> I am assuming any proposal would add inductance & resistance to
> replace the motor armature during the regenerating phase.
No; this is not (normally) necessary.
A PWM controller is more properly called a "buck converter". It requires
4 parts to function efficiently; 1 switch, 1 diode, 1 capacitor, and 1
inductor. The switch is usually a transistor; bipolar, MOSFET, or IGBT.
The diode is usually silicon or schottky. They sometimes "cheat" on the
capacitor and use the battery to provide some or all of the capacitance.
They also "cheat" on the inductor and use the motor's inherent
inductance when possible. Sometimes multiple devices are used in
parallel to save money.
A series motor has a lot of inductance, mainly provided by the field.
So, a separate inductor is rarely used with series motors. You *will*
sometime see separate inductors with PM or shunt motors to get them to
work right.
Any normal controller would have no trouble driving just the field of a
series motor. The only problem would be if you have a *really* large
series motor (like an Advanced DC 9") and a really small controller
(like a Curtis 1221B). This motor is known to have insufficient
inductance for this controller even wired normally (field and armature
in series), so using the 1221B to drive just the ADC 9" field would make
a bad situation worse.
Ok; so you can drive just the field. What happens next?
You are running the series motor as a "separately excited" motor. This
means a) Varmature = K x Speed x Ifield (where K is a constant for the
given motor). So yes; you could use the controller to run enough field
current so the armature voltage is greater than the pack voltage at any
given rpm.
But, there are problems. Series motors assume that field current =
armature current. The magnetic fields produced by the armature and field
windings "warp" each other. When the current in both are the same, each
is strong enough to "fight off" the other. But if you weaken the field,
the armature current will "warp" the field. The apparent position of the
field moves from its real position. This shifts the optimum position of
the brushes for minimum arcing. Thus, reducing the field current
compared to the armature current increases arcing.
So, this scheme has a problem at high motor rpm. The equation requires
low field current to get Varmature = Vpack. But then you can only allow
low armature current; thus low regen current.
As the vehicle slows down, you need to increase Ifield to increase
Varmature so it still matches Vpack. So, you can have more armature
current, i.e. more regen current. In other words, you get the least
regen at the highest speed, and the most at low speeds -- backwards of
what you normally want.
The standard method to avoid this situation is to keep the field and
armature in series, and rewire the PWM controller as a "boost
converter". A boost converter momentarily shorts the motor; this causes
a rapid buildup of current (but not voltage). Then it connects the motor
to the battery. A pulse of current flows into the battery. Then the
motor is shorted, and the process repeats. Because of field inductance,
the actual current ramps up 10-20% when the motor is shorted, and back
down 10-20% when connected to the battery.
The problem with this setup is that the motor armature is operating at
high current and low voltage during regen. This is a much less efficient
operating point for series motors. Also, you need to reverse the field
to get this kind of generator action. This requires a reversing
contactor. Finally, the brush position for minimal arcing changes
between forward and reverse; thus the brushes are in the WRONG position
during regen; when current is high and arcing is the worst.
The fix for *this* problem is to add compensating windings to the motor.
These are typically interpoles and/or pole face windings; smaller field
windings connected in series with the armature and positioned so they
counteract the effect of the armature current on the field. The drawback
of these windings is that they add cost and take up space (the motor
gets bigger, heavier, and costs more).
--
Ring the bells that you can ring
Forget your perfect offering
There is a crack in everything
That's how the light gets in
-- Leonard Cohen, from "Anthem"
--
Lee A. Hart 814 8th Ave N Sartell MN 56377 leeahart_at_earthlink.net
--- End Message ---
--- Begin Message ---
At 10:32 PM 14/03/05 -0500, Mike G wrote:
Great news I just found out that a newer fork truck is being scrapped at
work and I get to gut it for all of it's electrical components.
Now the bad news the truck was in a flood and everything is muddy and rusty.
I'm not to worried about the mud but the rust concerns me I want to try to
use this motor in my first conversion.
I will take the motor apart and replace the bearings and clean it as best
possible.
My question is it possible to check the armature for damage "shorted
windings" with a growler used for checking starter motors? The armature I
am talking about is pretty large it is from an 11 inch traction motor.
Any suggestions are appreciated.
Hi Mike
My motor was in a forklift that was partly wrecked and laid in a swamp
'paddock' that had it underwater some during a couple of winters. I
stripped it, washed it, cleaned it up, then spent $400 Australian (about
$280 US) with a motor shop who baked it and then tested it and renewed the
varnish where needed by painting it with epoxy. They also skimmed the
commutator and put new bearings in it. I think they put it on a 'growler'
to test for shorted turns, but I'm not certain of that.
It 'meggers' fine (very little leakage at 1000V) and runs nicely from low
voltage.
Since my motor dates from the 1960s' it is likely to be made with
relatively low temperature components. I intend to wind Kevlar thread
around the edges of the comutator, add thermocouples to a brush holder and
a field, add more epoxy 'paint' to smooth the airflow path and have the
rotor balanced (dynamically) before I put together finally to put the truck
on the road.
Check the hydraulic pump motor brush gear - it may be identical brushes and
holders to the traction motor, giving you spares. You may find brush
springs or spring tensioners to be rusted away (mine had a couple of spring
tensioner parts that had rusted through).
Don't forget the contactors, you may be able to clean them up to be
useable, too. The coil snubbers may be sealed and be OK.
You may be able to use some of the cables as they are (just clean the
terminal faces), but it would likely be very hard to get a good joint if
you were to cut the cables (due to the likelyhood of corrosion running up
the cables).
The potbox may be re-buildable, too.
It may have had a power-steering control module that detected steering
movement and drove the power steering hydraulic pump relative to that
movement - If, if maybe - grab it anyway.
I can't think of anything else, other than that a cabinet bead blaster has
been very handy in cleaning up parts to be re-used.
Good luck and have fun!
Regards
James.
--- End Message ---
--- Begin Message ---
Hi David (and all)
Comments inserted, I may have the wrong end of the stick or understumble
your intentions, but they may help your thought processes, or help bring up
points that others' may be able to help you prove/disprove your intentions.
At 06:10 PM 15/03/05 +1100, David Sharpe wrote:
Further to discussions with Lee:
I have been driving my converted Daihatsu and agonising over the
electrical braking situation at every traffic light. A solution that
might be feasible is to hit the field winding with current in the
opposite direction to motoring using two CTs (current transformer)
You may need to short out the CTs during normal driving, or the controller
switching pulses may cause big voltage spikes onto your drive gear (motor
inductance will smooth that out a lot, but acceleration rate-of-change will
need to be allowed for).
with
half bridge rectifiers. The high voltage side could be fed with a
converter but I will not deal with this at the moment. There is no need
to alter any topography to accommodate this.
Can you sketch (Ascii art) your proposed injection point/s and diode
positions? (I am having trouble visualising a system as you are describing).
What happens is that you hit the field with more current than the
current being supplied to the battery.
There is an error in your statement at this point, if you are braking, you
are coasting the motor, have no battery amps and decaying motor amps. Your
objective would seem to be to produce enough field strength of the correct
polarity to force the rotor voltage to exceed the battery pack voltage, to
achieve regenerative braking?
Perhaps this will be stable
enough with an appropriate control system to slow you. As speed reduces,
field Amps increases which is what you want. There should be a path
around the controller with existing diodes. I have not heard of this
idea before.
If I follow you, you intend to reverse the current through the field, in a
manner that enables you to be able to maintain current through the armature
and controller, whilst bypassing the field for the 'normal' current flow,
and injecting your regen current?
The braking current would be much less than a direct current injection
and should lessen the flux distortion/neutral axis issue.
If you don't get the magnetic flux density up enough, you will not be able
to generate more voltage than the battery, and won't get braking.
Regardless of where it comes from, the flux density HAS to be achieved
(unless I have confused/forgotton too much of mu theory).
Is there a flaw in my logic?
Not sure yet, but this should get plenty of interest, and microscopic
examination (unless someone points out a fatal flaw immediately, Rich?)
Regards
James Massey
Launceston, Tasmania, Australia.
--- End Message ---
