Generator - any ideas?

At the Wessex SEC D-Day crank up on Thursday, there was a generator of a
type I've not seen before. A small JAP industrial engine (throttled not
governed) drove two 12 volt car dynamos (not alternators), one direct drive,
the other vee belted from the shaft.
Photos here ........
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The last photos in this album.
The engine & dynamos are enclosed by a professional-looking steel tube
framework and a properly constructed panel at one one supported a couple of
boxes, one a standard Lucas FADE regulator & the other an aircraft 24 volt
box. There appears to be a diode (possibly a Zener) added on to one of the
bolts.
The interesting thing is that it produced 240 volts - or at least had done a
year ago. On Thursday it just produced noise & exhaust gas!
Rob Armstrong commented that he recalled seeing an article in an amateur
mechanics magazine just after the war which explained how to rewind a car
dynamo to be an alternator. He'd done so, eventually getting 110 volts out
of it - but it didn't last long!
If this is one of they, why two dynamos? & if it isn't why two dynamos at
all?
Any information would be much appreciated by both myself & the owner.
Regards,
Kim Siddorn
Reply to
kimsiddorn
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Kim,
Not wishing to be rude but it looks to me like a very well built home job, the welding and wiring is not what I would call a factory job.
Martin P
Reply to
campingstoveman
I think much as Martin does, that it is a home brew rather than a professional job.
The bolted-on device (gold coloured) is a wirewound resistor.
You would probably use two dynamos to get the required excitation voltage, as the basic frame and commutator size of a single dynamo wouldn't be sufficient, and there wouldn't be enough coils on the armature. Thus one is an ordinary dynamo, the output of which is used to drive the field of the second one.
To drive it to 240V implies a lot of voltage/current, which is probably why they don't last long!
Peter -- Peter & Rita Forbes Email: snipped-for-privacy@easynet.co.uk
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Reply to
Peter A Forbes
I thought that too until I considered that the wiring is almost entirely done in modern plastic. I suspect the original rubber stuff is long gone.
That said, it is at least possible that the frame is a reused professional frame. The bottom attachments don't look quite right.
But no ideas what it was for then?
Regards,
Kim Siddorn
Reply to
kimsiddorn
As Peter said , it's probably one dynamo generating excitation current for the second unit which has been converted to run as a "Rotary Converter" to make 240v. Bit of a lash-up but an interesting exercise in "making do with what he had"! By the way there should be an interesting old "Rotary Converter" on the club stall at Astle Park, if my Pal takes it!!
Reply to
Charles Hamilton
110V for tools? Portable arc welder?
Reply to
Andy Dingley
As usual where electrics are concerned, I don't get it & am not afraid to say so in order to be edificated!
So, dynamo A generates 12 volts - how do you feed that into dynamo B to "excite" the field? How is the wiring different in dynamo B in order for it to produce anything more than 12 volts?
Would it not be simpler to feed dynamo B from a battery?
Regards,
Kim Siddorn
Reply to
kimsiddorn
Not if You want a stable output. Voltage from batteries isn't exactly accurate or stable. 12volt car batteries can peak at nearly 15 volts at times. Company I worked for used to rewind motors for different voltages ie for mining applications etc, I had a book some where which explains it all in laymans speak. I'll try to find it for You!
Reply to
Charles Hamilton
No, as Charles has already said, the voltage won't be stable, and you'll need increased output with more load on the dynamo, which a battery won't give.
Plus you'll have the battery to look after and charge, so you may as well use a dynamo in the first place.
Remote excitation is usually fitted to enable generators to start up under load, as the usually field excitation from the generator output terminals doesn't happen in those circumstances.
Peter -- Peter & Rita Forbes Email: snipped-for-privacy@easynet.co.uk
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Reply to
Peter A Forbes

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