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Texas_Ranger #161761 04/07/07 02:09 PM
Joined: Apr 2006
Posts: 233
K
Kenbo Offline OP
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TR
As this is the first time I have tried anything like this I have not set myself too many goals. I would be happy just to light the odd light bulb at this stage.

The site that Alan listed is excellent for a jump off point for me.

If you are so worried about voltage and frequency why not generate 12v DC and put it through an inverter. I have one in my workshop rated at 300w and use it with a motor bike battery to run some 40w lamps. Which is charged from a solar pannel.

12 / 240 volt 1.5Kw invertor

Alan
Just pulled out my old "Haynes" for the old sierra I used to have. (Loved that old car) In the wiring diagrams I could not see any feed into the alternator. Only the output is marked in the diagrams, (don’t mean you are not correct) but I will nip down to the breakers yard tomorrow


der Großvater
Kenbo #161767 04/07/07 03:48 PM
Joined: Mar 2005
Posts: 1,803
Member
Ken, the car alternator terminals won’t show any “exiter” feeds, they’re part of the wiring loom and internal alternator diode circuit. The type of alternator fitted to cars is invariably the ‘rotor field’ type, because this alternator type’s output is easily controlled by varying the field current. Voltage regulation is built into the unit and modulates the small field current required, [say 2 amps], thus varying the output, which might be 60 amps or more. The rotor field is exited initially [ before the engine is started, normally ] by operation of the ignition key and through a ‘charge lamp’. When the engine starts, the alternator diode feeds such that it equalises volts across this lamp. This then ‘goes out’, [ although it’s probably is still running at a very small voltage], indicating that the alternator is charging.
Loss or failure to supply initial exitation current to the alternator means it won’t generate.
However if you are getting the parts from a breaker, it will be a simple matter to include an ignition lamp as part of the deal. Any 12v battery can supply the initial field current, say a cordless drill 12v ni-cad.

When wiring up the unit, follow Haynes’advice about terminal attachment - the alternator’s internal diode will not tolerate wrong polarity! Connect battery +ve first, negative last. Disconnect battery negative first, +ve last.

Finally, pedalling like fury, a human being is unlikely to generate more than about 150 watts. Bon courage!


Wood work but can't!
Texas_Ranger #161871 04/08/07 05:35 PM
Joined: Dec 2005
Posts: 869
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This motor will generate allright because of the strong magnets in the outer rotor which will provide all, excitation and running current.

Most car alternator can be rewired to access the 6 power diodes and 3 excitation diodes.

I have a simple but reliable 12 Volts charging regulator circuit, which works with discreet components, can be build for a couple of $$.

I have trialled it in 3 different cars for over 10 years with no problems with this circuit.
In my old Falcon XY i put in a ducellier alternator with this cct when the old Email alternator failed because of a mechanical regulator faillure. (ok i talk old cars here).
In a Rover P5b i put it in with the original lucas alternator.
In a Renault 16 it worked with the Paris Rhone alternator.

This circuit can be mounted on the firewall somewhere, in a small insulated box with the heatsink for the 2N3055 on top.


The product of rotation, excitation and flux produces electricty.
RODALCO #161872 04/08/07 05:47 PM
Joined: Dec 2005
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https://i123.photobucket.com/albums/o298/RODALCO/DSC01723.jpg

12 V car regulator schema.

D2, D3, D4 are the internal excitation diodes already present in the alternator.

By separating the two wires from the field brushes from the internal regulator, these wires can be taken outside to connect to this cct.
Sometimes the brush holders are part of the complete regulator assembly, and you need to try out what to disconnect to make it work.
You can even leave the old regulator in the alternator and isolate its supply.


The product of rotation, excitation and flux produces electricty.
RODALCO #161887 04/09/07 12:25 AM
Joined: Feb 2003
Posts: 288
Y
Member
As I understand it, the excitation current of most car alternators is a flat 5A, and it takes a pretty high RPM to get any reasonable efficiency. And yeah, the Scoraig windpower site is as good a resource as any for that.

yaktx #161916 04/09/07 06:31 PM
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If a 12 Volt battery is flat, the excitation current may be up to 2 Amps for a short period, in general when the battery is 80% full, the current may be 1.5 Amps, but will taper off quickly to about 500 mA's when the voltage reaches 13.7 Volts, and even less when the battery is full.

Most car alternators have excitation diodes which are rated for 1 Amps continuously.
OK i Talk 40 -60 Amps alternators here.
If you have a 100 Amp alternator the initial excitation current will be more in the range of 3 - 4 Amps.

For certain wind applications when there is no wind for certain periods the 300-500 mA excitaion current may drain the battery bank, a method used is to pulse the excitation, via the exc lamp, on and off for 1 second, every 20 seconds or so. If there is enough wind the alternator will excite itself immideately and start charging the battery.

I have built over the years various 3Ø rotary batterychargers to quickly charge heavy batteries, to start diesel engines, and have done quite a bit of testing on excitation circuits, so i have a good idea of these exc current.

Kind regards, Raymond


The product of rotation, excitation and flux produces electricty.
RODALCO #161932 04/10/07 05:31 AM
Joined: Dec 2001
Posts: 2,498
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Member
Well, it's not exactly a precise plan, just a vague dream... frequency and voltage should be stable enough to run light bulbs (the smallest problem), angle grinder, rotary hammer and similar tools.
Creating DC and running it through an inverter sounds nice but unfortunately contradicts the part of my dream about doing everything with technology that was readily available 50 years ago...

As I said, it's a dream thing.

Texas_Ranger #161941 04/10/07 11:38 AM
Joined: Apr 2006
Posts: 233
K
Kenbo Offline OP
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Limited success.
Got everything working this afternoon and it worked, grin but we could only get half a volt out of the alternator. 0.78 volts with some furious peddling. blush
Clearly we are not getting enough revolutions at the alternator. Still reasonably happy with that.
The guys are going to try using the induction motor as a generator next


der Großvater
Kenbo #161943 04/10/07 01:10 PM
Joined: Jul 2004
Posts: 787
L
Member
.78 Volt into what kind of load? Open circuit?

LarryC #161946 04/10/07 01:56 PM
Joined: Apr 2006
Posts: 233
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Kenbo Offline OP
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Yep open circuit. Measured with digital voltmeter

Should I have put a small load on it?
I have some 3watt varible resistors.


der Großvater
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