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Old 30th July 2008, 08:14 PM   #1
Clipped is offline Clipped  Thailand
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Default regulating a permanent magnet alternator

is there anyway to regulate the output of a permanent magnet alternator ?

these units swing anywhere between 12-70 volts depending on the rpm....they can get into the 70 volt range around the 4k-5k rpm range....but around 12volts under 1k rpm.

anyway to keep it steady between 14-16 volts but keep letting the amps rise ??? how would you go about doing this?


thanx
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Old 30th July 2008, 08:52 PM   #2
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use a voltage regulator (most preferably switching) after the alt. there's no other way electrically.

mechanically, maintain constant RPM.
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Old 30th July 2008, 09:20 PM   #3
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I think those were referred to as 'generators' instead of alternators. The old vehicles (pre 1970 - approximately) used a regulator like this one:
http://www.superiormustangparts.com/...d=C2AF-10505-B


If I remember correctly, it had contacts that would make/break to keep the voltage at a safe level.
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Old 31st July 2008, 02:51 AM   #4
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you could alternate between delta and star winding via magnetic contacts which activate once a set voltage is obtained, it would basicly be an electromagnet that closes the contact when the target is reached....but this just doesnt feel like the proper way to do it...maybe this is what that box does in your post perry.

hmmm...thinking of a way to keep constant rpm, i think i just came up with an idea...
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Old 31st July 2008, 04:05 PM   #5
Eva is offline Eva  Spain
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You can use an electronic circuit to skip pulses when the voltage exceeds a certain value. It may be controlled with a PIC or with logic gates and comparators. Rectification and switching may be achieved with Schottky diodes or thyristors or MOSFET (synchronous rectification).
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Old 31st July 2008, 04:47 PM   #6
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A standard switching buck regulator, perhaps a self-oscillating current-mode hysteretic design will do the job.

This type of alternator is often used coupled to a wind turbine or water turbine for 'green' power generation. If you want to make the best use of the power available from the alternator, then people now are looking at more sophisticated buck switching regulators that are able to provide the optimum load impedance to the alternator to give the best power matching for a particular rpm.
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Old 31st July 2008, 06:10 PM   #7
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interesting info, but its over my head... im making some axial generators with neo mags for emergency power generation as kind of a hobby now... but this regulation thing has got me stumped...
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Old 31st July 2008, 06:36 PM   #8
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More information on the generator may be helpful. The old style automotive generators had only 2 wires. What does yours have?

Why not use alternators if you need 12v? They have internal regulators, are readily available (if one needs to be replaced) and are relatively inexpensive.

If you have to use a permanent magnet generator and cannot control the output easily, post the requirements for the reg and someone here should be able to help.

Maximum/minimum input voltage?
Maximum continuous output current?
Surge current?
Output voltage (12v?, 13.8v?)?
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Old 1st August 2008, 07:57 AM   #9
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Axial-flux, permanent magnet alternators are pretty much a hot topic among the self-generated electricity crowd at the moment. As they have a large number of poles, they can give significant output at low rpm. There's plenty of information available on the web, with home-made designs using two car brake discs (rotors), together with a lot of NIB high-flux magnets (perhaps salvaged from old hard-disk drives), with the stator output windings sandwiched between. Commercially-made ones are also available, with some usually on Ebay. They are much superior to standard automotive alternators if you want to get efficient generation of energy from wind or water turbines.
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Old 1st August 2008, 04:24 PM   #10
Clipped is offline Clipped  Thailand
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yep you can get quite a bit more power from an axial design than a radial design, even with one rotor plate, ive been using small 3amp ac transformers dissected and rewound as the armature coils...

ive just been experimenting trying to get the 3 phase wiring right, finding 'correct' info is hard to find on the net...the 'B' phase has to start with 'B2'....not many sites explain this.

so this month im going to make the first 'real' generator instead of small mockups as i think i have it down now.

so i should have some numbers to throw out after i get the prototype made...

with all the electrical geniuses in here, i think this is a great place to develop a truly well designed regulator /motor controller since, it deals with more or less alot of the same circuits as car poweramps....for me all i can really handle is the actual construction of the generators/motors.

i bought some old hardrives for $1 a piece, but the mags are inconsistant in shape, and i believe for optimum output there should be spaces between N/S poles for maximum flux cutting, harddrive mags have 2 poles on the same face.

well for you guys that can design good circuits, Perry, Eva, etc.. .theres a market there for a good regulator design, battery charger, motor controller...everything is still relatively expensive.

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