Author Topic: Rewiring Allam generator  (Read 7932 times)

Blue

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Rewiring Allam generator
« on: November 06, 2013, 02:16:19 PM »
I have recently obtained a Petter AC2 with a 7.5 kva generator giving 415/ 240 vac. It is old so there is no 12 wire system in place. I looked ! I wonder if it would be possible to alter the
excitation current to get 240/ 120 vac. I don't need the three phase side of it at all. I will try and post a picture of the wiring diagram but as I posted stuff on the gallery a week ago which hasn't surfaced, I don't hold out much hope. Basically It has 3 excitation coils energised by a capacitor (or battery flash if it has been a while). Each are connected to one side of a transformers (three in total). This then comes through various diodes, to turn it into DC, and off down to the rotor via a brush. The other brush is connected to ground. On the ac side one side of each coil is joined and grounded. The other comes to the other end of the transformer and then off to the outlet sockets. What are the transformers doing ? Are they a kind of regulator that alters the excitation voltage depending on load? I give up with this picture cra.............!!!
Owned; Lister ST1, ST2, JP4, LD1 & 2x Blackstone ERS8. Petter AA1, AC2 and still up for it !!!

Schwen

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Re: Rewiring Allam generator
« Reply #1 on: November 06, 2013, 05:24:33 PM »
The transformers are probably part of the self regulation system. Without seeing the circuit diagram I'm supposing the "no load" field excitation current is from the AC circuit via the capacitors and diodes to give DC . Under load, once output current starts flowing through the transformers it induces a secondary current in the excitation circuit which is added to the "no load" current flowing through the capacitors, is rectified and increases the field strength to maintain the output voltage. The greater the output load, the greater the excitation current hence the self regulation.

Blue

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Re: Rewiring Allam generator
« Reply #2 on: November 06, 2013, 10:19:40 PM »
I will try and get a picture of the schematic wiring diagram that I have to upload but DON'T HOLD YOUR BREATH  >:(

Sorry just can't get it done. Don't know where the clipboard is in Windows 8 and can't retrieve anything. Bummer
Owned; Lister ST1, ST2, JP4, LD1 & 2x Blackstone ERS8. Petter AA1, AC2 and still up for it !!!

Tom

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Re: Rewiring Allam generator
« Reply #3 on: November 06, 2013, 10:26:00 PM »
Ctrl-V will paste anything in the clipboard. FYI Ctrl-X will cut and Ctrl-C will copy.
Tom
2004 Ashwamegh 6/1 #217 - ST5 just over 3k hours.

Blue

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Re: Rewiring Allam generator
« Reply #4 on: November 07, 2013, 12:28:54 AM »
Tom it just plays a little note when I try any of the above I'm afraid. Moving right along........... it has 90 vdc going in to excite it. If I was to reduce that ???? would it have the desired effect ?????????????
Owned; Lister ST1, ST2, JP4, LD1 & 2x Blackstone ERS8. Petter AA1, AC2 and still up for it !!!

Blue

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Re: Rewiring Allam generator
« Reply #5 on: November 07, 2013, 02:45:28 PM »
Just managed to post the wiring diagram in the gallery in my album Ian Cox
Owned; Lister ST1, ST2, JP4, LD1 & 2x Blackstone ERS8. Petter AA1, AC2 and still up for it !!!

magnicon

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Re: Rewiring Allam generator
« Reply #6 on: November 12, 2013, 02:26:43 PM »
Looking at that diagram I don't think there is much you can do with it,some transformer controlled machines had a few tappings or an adjustable air gap but these only gave about 5% variation and not the 50% you are looking for.7.5kva three phase output on a portable machine may seem a bit odd but I have seen these operating floor finishing machines on sites where no TP supply was available.
Allam generators were manufactured in Southend-on-sea,Essex.I think they went bust about 1979 or 1980.

Blue

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Re: Rewiring Allam generator
« Reply #7 on: November 12, 2013, 10:34:02 PM »
Thanks for that. There are no other places on the coils that I can tap into so as you say it looks like that's it. What about varying the excitation input? Would that work? It was used here for pumping water from a deep well in the middle of a field but industry here still uses 415/ 3 phase so I may find someone who can use it if the excitation idea doesn't float. Years ago I had a 48 vdc system on an old Dutch ship which had a large sliding rheostat for the excitation current but of course the more lights that went on the dimmer the lights would get until someone went and adjusted the rheostat.
Owned; Lister ST1, ST2, JP4, LD1 & 2x Blackstone ERS8. Petter AA1, AC2 and still up for it !!!