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Forum Index : Electronics : Dunlite 6kva generator AVR
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| Jacob89 Newbie  Joined: 10/09/2017 Location: AustraliaPosts: 39 |
I've come across this big old 6kva 4 pole Dunlite generator with a Lombardini diesel engine. I'm not sure if the engine runs yet but thats not really important, my main concern is getting the alternator running.  It has what seems to be an old style of AVR. At first I couldn't for the life of me figure out how it was supposed to work, until I realised that the field findings are stationary and the power windings are in the rotor. I've never seen an alternator set up like this but maybe it used to be more common. Basically there seems to be a transformer, the primary winding of which is in series with the load. So the greater the load, the more current through the primary and I guess the more current is produced in the secondary, which feeds the field. There is some capacitors and a contactor in the circuit, the purpose of which I haven't really gotten my head around.   I'm not sure its worth attempting to resurrect the original AVR, its not in great shape. I was originally going to throw a cheap universal AVR at it, but they seem to be made for more common rotating field generators with a field winding resistance of 10-100ohms and operate at about 90v. My field winding has a resistance of 140ohms. I'm guessing its designed to operate at a higher voltage (and therefore lower current). So I think I have three options: 1. Attempt to recondition the original regulator 2. Build a new AVR from scratch 3. Attempt to modify a cheap universal AVR to output a higher voltage. I wonder if the gurus here could offer some advice. Cheers |
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Madness Guru  Joined: 08/10/2011 Location: AustraliaPosts: 2498 |
You are right about the fixed field being more common previously. I have an Onan 10KW Diesel generator that I resurrected and the AVR was missing. It is the type with a brushless rotating field, I fitted one of these AVR boards. The only modification I made was to add a 5 ohm series resistor as the Onan had 7 or 8 ohms resistance, it works perfectly. It would be worth trying the same AVR with yours the higher resistance should not bother it but the high voltage might be an issue. However that AVR does work up to 90VDC, you may be able to use the new AVR to control a transistor with the existing transformer. There are only 10 types of people in the world: those who understand binary, and those who don't. |
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| Jacob89 Newbie Joined: 10/09/2017 Location: AustraliaPosts: 39 |
Thanks Mad, I'll give one of those a go. For $20-30 they aren't much load to carry, and if if doesn't work for this generator I may be able to use it on another one. |
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| Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498 |
For Stamford generators a standard test is to use a 12V battery to power the field which on those will give near the correct AC volts out with no load. There are only 10 types of people in the world: those who understand binary, and those who don't. |
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wiseguy Guru Joined: 21/06/2018 Location: AustraliaPosts: 1156 |
I have a few old Dunlite PDFs which may be of use to you - if not someone searching for Dunlite stuff might find them useful. 2018-10-21_173514_1021-73-1.pdf 2018-10-21_173535_DUN_UVR100.pdf They are possibly not old enough for the generator you have. I knew Lloyd Dunn personally, my dad managed a farm of his & he had a few of his Dunlite 32V wind systems operating there before we got mains connected. If at first you dont succeed, I suggest you avoid sky diving.... Cheers Mike |
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| Jacob89 Newbie Joined: 10/09/2017 Location: AustraliaPosts: 39 |
I thought I'd update this old thread because I did finally get the old girl up and running, and maybe it'll help someone else out some day. I did get the engine running and connected one of the chinese cheapy AVRs. It did work, but as I suspected the high resistance field windings need to see a much higher voltage than the chinese AVR can ouput in order to maintain a stable output with any kind of load. Essentially, the AVR had to run flat out at 100vdc to maintain the output at about 230vac with no load. Any load and the voltage dropped, because the AVR was already giving all it could. I thought about it for a while and posed the question to some engineers on another forum, but received no really useful suggestions. Scrap it and buy a new generator, spend big $$$ on an AVR that can output the higher voltage you need, that sort of thing. But the purpose of the exercise was to get this particular generator going and not spend a pile of money on it. I decided to take a closer look at the field windings. Being a four pole unit, there are four field coils in the stator, and they are connected in series. They are quite large coils and I suspect they have lots of turns, which explains the high resistance. So the simplest solution I found was to rewire them so that instead of all being in series, there are two pairs of two in series, in parallel. This means each coil sees a max of about 50v, instead of 25v as before. This doubles the current draw, of course, but its still well inside the rating of the AVR. It performs beautifully now. It actually belongs to my uncle now, and he's given it quite a flogging. He ran 5-6kw of halogen flood lighting off it, for probably 50 hours or so, and it took it like a champ. The Lombardini diesel is a horrible noisy thing though. |
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| Davo99 Guru Joined: 03/06/2019 Location: AustraliaPosts: 1578 |
I have a 5 Hp aircooled Lombardini, a Ruggerini and a bunch of China Diesels. I agree the lombardini is noisy but then again, none of them are quiet. My Hatz is probably the quietest by a good measure. The lombardini is rope start which I thought must have been a patch up job but they came like that from the factory. Good to hear you got the old gen head working. I used one of these AVR's on my brother in laws Battle ship generator a few years ago. Geez I hate anything marine. No matter what, everything is corroded and a pain to work on. I had my severe doubt as to how long any of it would work but it still is which I'm happy about not to have to stuff around in claustrophobic places again. I'm not a lightweight but I can't do anything about the width of my shoulders and the people that Build these boats must all be under the age of 10 yo way they shove things in to tiny paces. If anyone comes across a decent 3Kw+ twin bearing, Pulley driven capable gen head within reasonable reach of Sydney, Please let me know. Been looking for one for years that didn't have twice the asking Price I could buy a new complete setup for. |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
My old original 5Kva 12Hp single cylinder Wisconsin had a regulator similar if not identical to yours. It was horrible when it worked, voltages all over the place, and it would occasionally pin the 300 volt voltmeter at max. I was too afraid to connect anything up to it, it would pop light bulbs with ease. Never did figure out exactly how the voltage regulator was supposed to work. Your best bet is to use a modern electronic regulator, as suggested. A lot of this stuff is truly ancient and not worth trying to restore back to original. Much more sensible and practical to add some modern technology to it. Edited 2020-08-03 20:27 by Warpspeed Cheers, Tony. |
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| Jacob89 Newbie Joined: 10/09/2017 Location: AustraliaPosts: 39 |
Yeah I don't think any air cooled high speed diesels are ever going to be very quiet. My uncle has a couple of low speed 20hp twin cylinder Southern Cross diesels, I'm trying to convince him one of those would be much better match with the old dunlite alternator head. This lombardini is a rope pull only as well, and being 14hp and with no decompressor, it definitely requires the right technique to start. I had one exciting incident before I had it down pat, where the engine fired up and wound the pull rope back in. Yanked the handle out of my hands, smashed the handle to pieces and ripped the fuel line off the tank. I'd made the handle out of pvc conduit and I was picking up shards of it for days. Lucky I didn't catch a piece in the eye. |
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| Jacob89 Newbie Joined: 10/09/2017 Location: AustraliaPosts: 39 |
Yeah pretty impressed with the output stability of the new AVR. I don't exactly how old this thing is but there is a capacitor in the there that is made in Australia and was discontinued in the sixties, and I actually found it on a list of components known to contain PCBs. No point messing around with it. |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
I just found my old original regulator, thought I had tossed it out long ago. Very similar to yours, 20uF oil filled capacitor, current transformer, and big screw terminal block.  Cheers, Tony. |
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