Adjustable voltage regulator for car alternator
marcus
automatic regulator circuit
to control a 24V car alternator?
Application is deep-cycle solar battery charging using 3-5HP small petrol
motor coupled to 24V alternator.
Need to tweak the voltage up to about 29-30V to equalise the batteries.
Solar batteries like a 3-stage charging regime - boost, bulk & float. These
voltages are all diff. and also depend on battery type (chemistry), so the
field needs to have these adjustable set-points.
Would be nice to be able to sense battery voltage and feedback into
alternator field voltage, to make a set-and-forget circuit.
Here's some background (12V, and no feedback) :
http://www.homepower.com/files/mark8.pdf
Thanks to everyone in aus.electronics who had a look at this.
Jim Thompson : I notice from your web pages that you have designed some car
alternator regulation projects - wondering if you have any thoughts?
Thanks all
Marcus in outback Oz
Jim Thompson
Of course. (Most of my early patents were automotive products.)
Early next week... I'm buried with work this weekend.
Flat voltage or do you need temperature compensation?
...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |
America: Land of the Free, Because of the Brave
Jim Thompson
Also, Is field tied to A+ end or ground end of alternator?
marcus
I do have a temp. sensor setup already going into my Plasmatronics
regulator, so I could use a temp. compensated circuit, at the risk of
complexity/your time.
I haven't procured/scrounged the alt. yet, so I don't know about it's
field - should I look for one setup in particular?
Thanks so much,
Marcus, in outback Oz @ 23.7VDC, so not too much juice left in batteries
tonight!!
MooseFET
I'm going to say this before anyone else does: "Use a PIC"
This truely may be a good job for a micro controller witha built in
ADC. I would use a good reference and a R-R op-amp and a few
resistors to scale and offset the input to the ADC. Assuming 4 x 8
bit ADC channels, I would allocate them something like this:
Chan Meaning
0 0..255 = Battery voltage 26..32
1 0..255 = Battery voltage 0..32
2 0..255 = Thermistor 60C..-20C
3 0..255 = Charging current 0 .. 2xBattery rating
Channel 1 is used to look at the battery voltage in the non-charging
state. Channel 0 is supposed to have the fast charge stopping point
near the middle of its span.
You may also want a logic input to tell you that the alt. is spinning.
The field drive would be done as a PWM control at some fairly low
frequency. The field coils have a very large inductance but it is
very lossy at high frequencies.
The only part of the software that needs to be at all quick is the bit
that regulates the charging current.
Jim Thompson
It's a little easier if the field is tied to A+, then the switching
can be done to ground via a power NMOS, or NPN... avoiding a high-side
driver problem.
As for those who suggest a PIC... what a pile of crap. Analog is
trivial in this application. Can a PIC provide 5A ?:-)
marcus
Thanks for the PIC idea - I have thought longingly about this, and I know it
would have advantages - but as far as micros go, I'm only up to trying to
decide which programmer to get and having received a few samples from
Microchip, so I am resigned to a "dumb" design for the time being.
Marcus in Oz; 2:58AM and batteries now @ 22.9VDC - getting low!
marcus
Any ideas how to tell quickly if I have a suitable alt. with say my
multimeter in the local junkyard.
I can look up common models on the net of course.
thanks all,
Marcus in off-grid outback
Jim Thompson
Measure resistance between field terminal to A+, and field terminal to
ground.
Desired is resistance to A+ (field connected to A+ internally).
MooseFET
Web-Site.com> wrote:
> On Sun, 22 Apr 2007 01:15:43 +1000, "marcus" <1...@344.445> wrote:
> >Thanks, Jim for the reply ~
>
> >I do have a temp. sensor setup already going into my Plasmatronics
> >regulator, so I could use a temp. compensated circuit, at the risk of
> >complexity/your time.
>
> >I haven't procured/scrounged the alt. yet, so I don't know about it's
> >field - should I look for one setup in particular?
>
> >Thanks so much,
>
> >Marcus, in outback Oz @ 23.7VDC, so not too much juice left in batteries
> >tonight!!
>
> It's a little easier if the field is tied to A+, then the switching
> can be done to ground via a power NMOS, or NPN... avoiding a high-side
> driver problem.
>
> As for those who suggest a PIC... what a pile of crap. Analog is
> trivial in this application. Can a PIC provide 5A ?:-)
Sure just hook about 28V onto it. More than 5A will come out of
whatever pin is connected to the expensive parts.
default
I couldn't see the file you reference.
but
12 volt alternators can put out 14 volts at idle so with just a pulley
adjustment or running them faster the voltage goes up proportionately.
From that point on it is just a matter of a regulator.
I have a two transistor regulator that I scrounged from a Chilton's
manual back in '72. They didn't show component values, but I put what
I thought would work and it did in a BMW motorcycle and Toyota Land
Cruiser. Doesn't do anything fancy like float at a lower voltage, but
I could post the schematic if you want or email it.
Very simple device - NPN pass transistor is biased "on" with a
resistor (turning on the rotor) and a second transistor turns it off
when the Zener/ and potentiometer-setting voltage is exceeded. The
Chilton's manual showed fixed resistors - I used a military spec wire
wound pot to set the voltage.
The BMW reg was in the bike for 10 years (in the weather) and I had no
problems with it other than painting the transistors so the TO66 cases
wouldn't rust through - on the land cruiser I used a 2N3055 and it
never rusted in the engine compartment. No heatsink was needed - the
rotor would pull about 3 amps maximum.
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Homer J Simpson
"marcus" <1...@344.445> wrote in message
news:462a4c5d$0$83730$c30e...@pit-reader.telstra.net...
Have you looked at Silicon Chip (AU)?
http://www.siliconchip.com.au/
http://www.siliconchip.com.au/cms/A_103233/article.html
http://www.siliconchip.com.au/cms/A_30620/article.html
If you are in Oz your library may have back copies you can read for free.
kell
I agree with Jim about going analog. I've built more than one voltage
regulator for old vehicles I've owned. Building a simple analog
voltage regulator and getting it to work is relatively easy.
I got the basic idea from this website:
http://homepage.sunrise.ch/mysunrise/joerg.hau/mot/voltreg.htm
The voltage regulator on that web page is for a grounded field
alternator. If you want to use the kind of alternator Jim suggested,
flip the diagram upside down and reverse the polarities. GM (Delco)
alternators for example have the kind of field Jim is talking about.
Field is tied to the high end, and you do the switching at ground.
The guy that designed the voltage regulator on the website suggests
jumpers (you could use switches) across diodes in the string to set
the voltage. If you want finer resolution in the voltage setpoint you
could put a shottky in the series.
Or you could work it out a little differently with a potentiometer/
voltage divider scenario, for continuous voltage adjustment.
I used a mosfet instead of the darlington in the diagram. The
hysteresis in Joerg's circuit minimizes heat in the switching element
by making it switch on and off in a narrow band around the setpoint
instead of going into linear operation.
Final note. A great website for RE stuff is
www.fieldlines.com
RW Salnick
You can buy one for less than $20.
Are you talking about converting a 12V nominal automotive alternator to
24V? You won't need to make any changes to the pulley to make the
alternator deliver 24 V, but the the diodes and the diode trio will need
to be replaced with 24V versions.
And the new regulator, of course.
bob
s/v Eolian
Seattle
John Popelish
(snip) You won't need to make any changes to the pulley to
> alternator deliver 24 V, but the the diodes and the diode trio will need
> to be replaced with 24V versions.
Are you seriously suggesting that a 12 volt alternator is
made with a diode trio that cannot handle 24 volts? I was
under the impression that few silicon rectifiers are made
with a breakdown voltage less than 50 volts.
Michael A. Terrell
What PIV diodes do you think you need for 24 volts?
--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.
Michael A. Terrell
Central Florida
Carl Ijames
>> automatic regulator circuit
>> to control a 24V car alternator?
The crude way is to use a voltage divider on the sense input. For the
GM 12 V 120 A alternators used on the 86-87 turbo V6 Regals, an example
diagram is at: http://www.gnttype.org/techarea/projects/gnalt.html The
idea is to use a throttle or boost actuated switch to kick up the output
voltage to give the ignition and fuel pump a boost at wide open
throttle. On these alternators the dash volts light is a 194 and it
goes from battery to the L pin on the 4 pin connector, to provide both
sensing input and idiot light. The internal resistance of this bulb is
crucial, you will blow things up if it is shorted and make things very
unhappy if it is open. The S terminal, on the other hand, is for
sensing only and can be connected directly to the battery. I don't know
the limits on output voltage but 16 V is what is commonly used in
racing - enough to make a real difference in ignition and fueling but
not quite start popping lightbulbs during a sub-12 second quarter mile
blast :-). This works on all the GM alternators I've seen from the 70's
and 80's. Somewhere in the 90's the engine computer started controlling
the alternator and I'm not familiar with the details on those. A
commercial external regulator (I think; it may just be a divider too) is
available from Precision Turbo & Engine in Indiana, USA.
--
Regards,
Carl Ijames carl dott ijames aat verizon dott net
(remove nospm or make the obvious changes before replying)
RW Salnick
They need to be able to handle *at least* double the intended voltage
delivery. A 24 V alternator will probably actually deliver 28V (just as
today's 12 V alternators are delivering as much as 16V).
bob
John Popelish
> John Popelish wrote:
>> RW Salnick wrote:
>> (snip) You won't need to make any changes to the pulley to
>> make the
>>> alternator deliver 24 V, but the the diodes and the diode trio will need
>>> to be replaced with 24V versions.
>> (snip)
>>
>> Are you seriously suggesting that a 12 volt alternator is
>> made with a diode trio that cannot handle 24 volts? I was
>> under the impression that few silicon rectifiers are made
>> with a breakdown voltage less than 50 volts.
>
>
> What PIV diodes do you think you need for 24 volts?
Need? 35 volts should be enough to work, but I would like
at least 100 volt.
What PIV diodes do you think they put in the trio?
Michael A. Terrell
You are forgetting that when the diode is off, it also has the
battery voltage added to the AC from the alternator, so the bare
minimum would be 24 VDC +(24*1.414=33.936-.6) 33.336, or 57.336 PIV, if
there are no spikes or inductive surges. A load dump can be several
hundred volts, and the diodes have to survive.
> What PIV diodes do you think they put in the trio?
The last set I replaced were unmarked. All they had was an OEM part
number. One of the trios opened on the way home from Orlando after
midnight one night. I was laying in wet grass and sand removing the high
output alternator from my stepvan, only to find it was too big to fit my
car. I had to strip both alternators and transplant the diodes to get to
work on time.
John Popelish
> John Popelish wrote:
>> Michael A. Terrell wrote:
>>> John Popelish wrote:
>>>> RW Salnick wrote:
>>>> (snip) You won't need to make any changes to the pulley to
>>>> make the
>>>>> alternator deliver 24 V, but the the diodes and the diode trio will need
>>>>> to be replaced with 24V versions.
>>>> (snip)
>>>>
>>>> Are you seriously suggesting that a 12 volt alternator is
>>>> made with a diode trio that cannot handle 24 volts? I was
>>>> under the impression that few silicon rectifiers are made
>>>> with a breakdown voltage less than 50 volts.
>>>
>>> What PIV diodes do you think you need for 24 volts?
>> Need? 35 volts should be enough to work, but I would like
>> at least 100 volt.
>
>
> You are forgetting that when the diode is off, it also has the
> battery voltage added to the AC from the alternator, so the bare
> minimum would be 24 VDC +(24*1.414=33.936-.6) 33.336, or 57.336 PIV, if
> there are no spikes or inductive surges.
I'm not forgetting anything, that is not how it works.
there is a 3 phase bridge rectifier across the AC with the
negative side of the output to ground (so no AC swings can
go more negative than a diode drop below ground). There are
two positive sides to this bridge, connected in parallel to
the 3 phase AC. One set of 3 provides the DC output to the
battery, and the other 3 diodes provide the DC to the field
excitation regulator. But, since the 3 to the battery
prevent the AC from exceeding the battery voltage by more
than a diode drop, None of these 9 diodes sees more reverse
voltage than the battery plus a diode drop.
> A load dump can be several
> hundred volts, and the diodes have to survive.
This, I agree with, and this is why the main rectifiers as
well as the trio diodes all have PIV ratings in the hundreds
of volts.
> What PIV diodes do you think they put in the trio?
>
>
> The last set I replaced were unmarked. All they had was an OEM part
> number. One of the trios opened on the way home from Orlando after
> midnight one night. I was laying in wet grass and sand removing the high
> output alternator from my stepvan, only to find it was too big to fit my
> car. I had to strip both alternators and transplant the diodes to get to
> work on time.
What does this failure tell us about the PIV rating of the
trio? Not much, I think. You don't know that thew trio
failed from excessive voltage. Could have been a bond
failure that overheated one of them.
Michael A. Terrell
>
> What does this failure tell us about the PIV rating of the
> trio? Not much, I think. You don't know that thew trio
> failed from excessive voltage. Could have been a bond
> failure that overheated one of them.
All three diodes were open.
John Popelish
> John Popelish wrote:
>> What does this failure tell us about the PIV rating of the
>> trio? Not much, I think. You don't know that thew trio
>> failed from excessive voltage. Could have been a bond
>> failure that overheated one of them.
>
>
> All three diodes were open.
So what do you conclude caused this failure, if anything?
Michael A. Terrell
I have no idea. All I found was four lugs and burnt plastic ash.
There was nothing left to do failure analysis on.
John Popelish
> John Popelish wrote:
>> Michael A. Terrell wrote:
>>> John Popelish wrote:
>>>> What does this failure tell us about the PIV rating of the
>>>> trio? Not much, I think. You don't know that thew trio
>>>> failed from excessive voltage. Could have been a bond
>>>> failure that overheated one of them.
>>>
>>> All three diodes were open.
>> So what do you conclude caused this failure, if anything?
>
>
> I have no idea. All I found was four lugs and burnt plastic ash.
> There was nothing left to do failure analysis on.
I would suspect an intermittent short between the rectifier
output and ground. But, I guess, if a high enough voltage
transient occurred, it could have shorted a rectifier and
then that short blew the other two. Of a diode bond failed
enough to overheat one die, causing the same cascade.
But do you agree with my analysis of the normal voltage
applied to these diodes? You clipped it without comment.
marcus
I already have a Plasmatronics regulator for my solar panels but I need an
adjustable AVR to control a 24V alternator driven by a 3 - 6 HP stationary
engine. It needs to handle 50A and sense the battery voltage.
I have just about every issue of SC - great magazine. It was a great shame
about EA magazine - I wonder whatever happened to Graham Cattley the editor
who ruined it in only a few issues?
marcus
marcus
It's my understanding of alternator operation that the voltage is
"built-in" by the number of poles, the number of turns on the rotor/stator,
and least of all by the regulator.
The speed controls current, not voltage.
If the regulator is removed (or the reg.'s ability to reduce the field
current is removed), then the alternator voltage will rise to over 100 V.
(OK for US -
you could get mains power straight from output - either AC or DC, at a high
frequency,
but I need 240VAC in Oz.) I believe a large alternator [200A] might produce
around 7200 Watts when driven this way. It would probably need 2 belts and
12 HP to drive it at this level, assuming bearings, heat, diodes, etc. were
upgraded.
What I want to do is charge a bank of solar batteries at up to a C20 rate
(about 40A in my case), with a 24V alternator driven by a 3- 6HP stationary
engine, with an adjustable regulator circuit that will provide up to 30VDC
and taper the charge as the batteries fill.
Great booklet about alternators :
www.1stconnect.com/anozira/SiteTops/energy/Alternator/alternator.htm
cheers all,
Marcus in Oz @ 28.4VDC (Sunny day!)
Homer J Simpson
"marcus" <1...@344.445> wrote in message
> I already have a Plasmatronics regulator for my solar panels but I need an
> adjustable AVR to control a 24V alternator driven by a 3 - 6 HP stationary
> engine. It needs to handle 50A and sense the battery voltage.
If it was me, I would look at controlling the engine speed to control the
charging. This will give maximum efficiency per litre of gas - this is
expensive electricity.
> I have just about every issue of SC - great magazine. It was a great shame
> about EA magazine - I wonder whatever happened to Graham Cattley the
> editor who ruined it in only a few issues?
I subscribed for many years back when it was Radio, TV & Hobbies (I think).
Eagerly awaited it every month - sad, but most all of the electronics
magazines have died now.
default
>Thanks to everyone who's contributed ideas to this thread.
>
>It's my understanding of alternator operation that the voltage is
>"built-in" by the number of poles, the number of turns on the rotor/stator,
>and least of all by the regulator.
>The speed controls current, not voltage.
Speed controls voltage, not current - wire size determines current. I
think it was Homer that suggested you try to regulate engine speed for
maximum efficiency from a gas engine.
>
>If the regulator is removed (or the reg.'s ability to reduce the field
>current is removed), then the alternator voltage will rise to over 100 V.
>(OK for US -
>you could get mains power straight from output - either AC or DC, at a high
>frequency,
>but I need 240VAC in Oz.) I believe a large alternator [200A] might produce
>around 7200 Watts when driven this way. It would probably need 2 belts and
>12 HP to drive it at this level, assuming bearings, heat, diodes, etc. were
>upgraded.
>
>What I want to do is charge a bank of solar batteries at up to a C20 rate
>(about 40A in my case), with a 24V alternator driven by a 3- 6HP stationary
>engine, with an adjustable regulator circuit that will provide up to 30VDC
>and taper the charge as the batteries fill.
>
>Great booklet about alternators :
>www.1stconnect.com/anozira/SiteTops/energy/Alternator/alternator.htm
>
>cheers all,
>
>Marcus in Oz @ 28.4VDC (Sunny day!)
>
>
>
--
default
<carl....@nospm.verizon.net> wrote:
>On these alternators the dash volts light is a 194 and it
>goes from battery to the L pin on the 4 pin connector, to provide both
>sensing input and idiot light. The internal resistance of this bulb is
>crucial, you will blow things up if it is shorted and make things very
>unhappy if it is open.
The idiot light supplies the current to magnetize the field until the
alternator is producing power. The light goes from the positive of
the ignition circuit to the field. There's an additional set of three
positive diodes on the alternator that also go to the field - when the
alternator is producing its own power, the light bulb has positive
voltage on both terminals and doesn't light.
Good design to use the alternator itself to supply the field through
isolation diodes - a shorted rotor won't output enough current to
destroy the regulator that way.
Short the lamp and you may destroy the regulator or rotor or both -
too high a lamp resistance and it will change the point where the
alternator begins charging or keep it from charging.
The lamp serves two purposes - tells you the alternator is working and
supplies current to the field to start the alternator working.
MooseFET
wrote:
> John Popelish wrote:
>
> > Michael A. Terrell wrote:
> > > John Popelish wrote:
> > >> What does this failure tell us about the PIV rating of the
> > >> trio? Not much, I think. You don't know that thew trio
> > >> failed from excessive voltage. Could have been a bond
> > >> failure that overheated one of them.
>
> > > All three diodes were open.
>
> > So what do you conclude caused this failure, if anything?
>
> I have no idea. All I found was four lugs and burnt plastic ash.
> There was nothing left to do failure analysis on.
That rules out the simple bond opening failure. It could be a case of
run away overheating that eventually led to molten diodes. All diodes
will work as an incandescent LED for a while after which they usually
go open. This could be what happened to them.
MooseFET
> "marcus" <1...@344.445> wrote in message
>
> news:462d98f3$0$37329$c30e...@pit-reader.telstra.net...
>
> > I already have a Plasmatronics regulator for my solar panels but I need an
> > adjustable AVR to control a 24V alternator driven by a 3 - 6 HP stationary
> > engine. It needs to handle 50A and sense the battery voltage.
>
> If it was me, I would look at controlling the engine speed to control the
> charging. This will give maximum efficiency per litre of gas - this is
> expensive electricity.
If you want to squeeze every ounce out, I think you will end up
controlling both. Strangely enough, I see an increase in field
current when less charging current is needed.
Take the over simplified model of the generator's performance as:
Volts(Open ckt) = K1 * Field * RPM
Amps = K2 * Torque / Field
Also over simplifying: Assume that the engine's torque for most
efficient operation remains constant. ie: full throttle on an engine
with no tuned ports.
To lower the current we actually want to increase the field. To make
the current lower, we also need Volts to go lower so the RPM must
decrease by more than the factor we reduced the current.
MooseFET
> Thanks to everyone who's contributed ideas to this thread.
>
> It's my understanding of alternator operation that the voltage is
> "built-in" by the number of poles, the number of turns on the rotor/stator,
> and least of all by the regulator.
> The speed controls current, not voltage.
No, this is not correct. The open circuit voltage is given by the
rate of change in magnetic field the stator sees. This means that it
varies with the RPM.
default
>On Apr 23, 11:24 pm, "Homer J Simpson" <nob...@nowhere.com> wrote:
>> "marcus" <1...@344.445> wrote in message
>>
>> news:462d98f3$0$37329$c30e...@pit-reader.telstra.net...
>>
>> > I already have a Plasmatronics regulator for my solar panels but I need an
>> > adjustable AVR to control a 24V alternator driven by a 3 - 6 HP stationary
>> > engine. It needs to handle 50A and sense the battery voltage.
>>
>> If it was me, I would look at controlling the engine speed to control the
>> charging. This will give maximum efficiency per litre of gas - this is
>> expensive electricity.
>
>If you want to squeeze every ounce out, I think you will end up
>controlling both. Strangely enough, I see an increase in field
>current when less charging current is needed.
YOU see an increase in field with less charging current - You really
want to think about that statement moosefet. If the regulator is
kicking in it does decrease the field current as the output voltage
goes up - and increases the field as the output drops.
Is it just possible that there's enough "runout" (out of round or
offset from the axis) in the slip rings? that may cause the brushes
to press lightly on the rings, or to leave the rings entirely? as
speed voltage and current try to increase - my own observation.
In your alternator - in theory (and from my own observation) the
speed, number or turns, and magnetic field determine voltage - period
(aside, perhaps, from winding temperature which is negligible).
>
>Take the over simplified model of the generator's performance as:
>
>Volts(Open ckt) = K1 * Field * RPM
>Amps = K2 * Torque / Field
>
>Also over simplifying: Assume that the engine's torque for most
>efficient operation remains constant. ie: full throttle on an engine
>with no tuned ports.
>
>To lower the current we actually want to increase the field. To make
>the current lower, we also need Volts to go lower so the RPM must
>decrease by more than the factor we reduced the current.
>
You'd better state the exact conditions before you try to sell that
idea. You're talking about the field (?) increase current (stronger
field) and you increase output voltage - and with a load - output
current - and torque load on the engine.
>
>
>>
>> > I have just about every issue of SC - great magazine. It was a great shame
>> > about EA magazine - I wonder whatever happened to Graham Cattley the
>> > editor who ruined it in only a few issues?
>>
>> I subscribed for many years back when it was Radio, TV & Hobbies (I think).
>> Eagerly awaited it every month - sad, but most all of the electronics
>> magazines have died now.
>
From my experience, if I see something like decreasing output power
(current and voltage) as the speed increases it is just telling me
that the brushes are "floating" (not tracking the slip rings at that
speed). Either increase the spring tension or fix the out-of-round
condition.
I'm guessing/thinking that you are seeing some anomaly and haven't
pinned it down to the real cause. Like brush float, self-induced
voltage in the rotor, etc..
My old Land Cruiser used a single coil electro- mechanical regulator.
At slow speed, the contacts stayed "normally closed," really driving
the rotor with a lot of current. At mid speed the contacts opened
and a resistor supplied some current to the rotor (you could see the
armature hover between contacts). At high speed the rotor was shorted
- I assume the self-induced magnetic field was keeping the output
voltage up.
It was clunky and expensive and I replaced it with a solid state
regulator - but I really really think that electro mechanical
regulator was using a self-induced voltage/field at high speed.
BTW the '72 Toyota $60 mechanical regulator could be replaced by a '67
Dodge electro mechanical regulator for $ 6 (in '78). About once a
year - until I used a solid state regulator.
Regulating engine speed is not trivial - since it requires some real
engineering talent - but is the "only" good way to do it.
With batteries supplying the invertors(s) there's no need to regulate
the field - unless the battery bank is small and the load changes
rapidly and to extreme power requirements - better to regulate engine
speed for efficiency.
And you'd want it "fail safe." - all the control circuits turn to
mush - you'd still want to protect the engine, alternator and
batteries. Easy enough - but necessary.
Franc Zabkar
to keyboard and composed:
>What I want to do is charge a bank of solar batteries at up to a C20 rate
>(about 40A in my case), with a 24V alternator driven by a 3- 6HP stationary
>engine, with an adjustable regulator circuit that will provide up to 30VDC
>and taper the charge as the batteries fill.
>
>Great booklet about alternators :
>www.1stconnect.com/anozira/SiteTops/energy/Alternator/alternator.htm
>
>cheers all,
>
>Marcus in Oz @ 28.4VDC (Sunny day!)
Can you relax your requirement to just a current limited 40A, 28.4VDC
constant voltage regulator? If so, then the required circuit would be
extremely simple, ie a 40A 600mV current shunt, 3 or 4 transistors, a
few diodes and a few resistors. The current limiting circuit (one
shunt and one transistor) would ensure that the current never exceeded
40A, even at low states of charge.
Temperature compensation could also be provided by a string of 1N4148
diodes.
If you are happy with this, then I will draw up a circuit for you.
- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.
John Popelish
> On 24 Apr 2007 06:50:55 -0700, MooseFET <kens...@rahul.net> wrote:
>
>> On Apr 23, 11:24 pm, "Homer J Simpson" <nob...@nowhere.com> wrote:
>>> "marcus" <1...@344.445> wrote in message
>>>
>>> news:462d98f3$0$37329$c30e...@pit-reader.telstra.net...
>>>
>>>> I already have a Plasmatronics regulator for my solar panels but I need an
>>>> adjustable AVR to control a 24V alternator driven by a 3 - 6 HP stationary
>>>> engine. It needs to handle 50A and sense the battery voltage.
>>> If it was me, I would look at controlling the engine speed to control the
>>> charging. This will give maximum efficiency per litre of gas - this is
>>> expensive electricity.
>> If you want to squeeze every ounce out, I think you will end up
>> controlling both. Strangely enough, I see an increase in field
>> current when less charging current is needed.
>
> YOU see an increase in field with less charging current - You really
> want to think about that statement moosefet.
I think this conclusion includes adjusting the engine speed
and alternator excitation current, simultaneously, to obtain
the optimum fuel to electric power conversion efficiency,
not a fixed speed (governor controlled engine), variable
excitation current situation.
I could be wrong about this.
marcus
Thanks for your offer of a circuit - can I take you up on that?
thanks
Marcus, in the rain!! (first time in about 3 months....)
Terry K
...and, it varies with the field current.
Terry k
Franc Zabkar
to keyboard and composed:
>Frank ~
This is the basic idea:
http://www.users.on.net/~fzabkar/alt-reg.JPG
If you have a grounded field alternator, then the field section of the
circuit needs to be modified. You also need to know the battery's
temperature coefficient before you can select your string of diodes.
Silicon diodes have a tempco of -2mV/degC, but zeners can have either
positive or negative tempcos that depend on the zener voltage. IIRC,
zener tempco is zero at around 5 or 6V. An alternative place to put
the signal diodes would be in the voltage divider.
I have added a momentary start switch just in case the residual
magnetism in the rotor is insufficient to self excite the alternator.
I have avoided using the "charge" lamp that normally provides this
function because the batteries would slowly discharge through it if
the motor were to stop.
One other thing you might like to consider is an overvoltage monitor
that trips a contactor if the regulator fails.