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Author Topic: SDA /SDT Generator Manual copy available and question on de-magnetised generator  (Read 3640 times)

ajaffa1

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Hi Alex, can`t do this tonight because it is black as pitch outside and well past my bed time. In the morning I will get some more ohm readings for you to compare and then talk you through flashing the main field windings. Photos of what you have done would help.

Bob

Alexdick

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Bob
See photo below
The rheostat is connected to the sine screws as is the top box and the rotator arm.
positive and negative are, I believe, correct....the negative is the higher of the two where it goes into the windings.
thanks
alex

Alexdick

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Bob
Further to my post above Iíve had a thought.... when I flashed the rheostat wires a few weeks ago, was the engine meant to be running? It wasnít...
Alex

mike90045

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Bob
Further to my post above Iíve had a thought.... when I flashed the rheostat wires a few weeks ago, was the engine meant to be running? It wasnít...
Alex

When I do mine, it's with all gear shut down.  The flash provides some residual magnetization which allows the generator to produce power.    Just disconnect loads before it spins down.  Spinning down with a load, erases the residual mag.

glort

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Bob
Further to my post above Iíve had a thought.... when I flashed the rheostat wires a few weeks ago, was the engine meant to be running? It wasnít...
Alex

You can do it running or not. Not running is generally the prefered method for safety reasons. If you are brave or just stupid, You can do it running which is what I tend to do which speaks for itself.  Another effective but non approved way to get the windings saturated is to give the engine a good rev above normal engine speeds to spin the gen head faster. Even 10 % helps a lot.

Again, the head has to be completely unloaded or you could be there for eternity and still get no where.

ajaffa1

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Hi Alex, before anyone goes flashing anything, I want you to do a couple of resistance tests for me.

The first is the resistance between the two AC output connectors in the top box. Mine reads about 3 ohms.

The second is the resistance between the two slip rings, please insulate the four carbon brushes with pieces of paper as per the photo and then stick your ohm meter probes onto the two rings. Mine shows a resistance of between 0.6 and 0.7 ohms.

The third thing I want you to do is to disconnect one wire from the larger rheostat in the front of the generator. See photo. One of the two wires is connected to neutral and the other is connected to the main windings, we need to know which is which.Please put one of your probes onto a clean bolt or screw on the body of the generator, now touch the other probe onto each of the two wires in turn. One of them should give a reading of 0 ohms, this is the neutral wire. Please mark it with a piece of insulation tape so we know that is the neutral.

Next I want to know the resistance between those two same wires. Mine reads 8.2 ohms.

Please report back with your findings.

Bob

ajaffa1

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Hi Alex, I`m thinking we have got a couple of the wires on the rectifier muddled up. Please see the documents and edited photos attached. Please also disconnect the two radio suppression condensers from the slip ring brush holders before doing your tests, as these can play havoc with the readings.

Bob

listeroil

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Bob
Hi Listeroil, perhaps you can explain to me how these are wound as tight as they are without any insulation. Did they acid etch them or coat them with something to to stop them from shorting between the windings?


I did not consider insulation just wound it up as tight as I could and used it. It worked okay.  However it makes sense to use insulated so I checked the website and they do sell oxidised wire and that appears to be insulated.One thing I will say is that all the resistors in Lister top boxes that I have seen have black windings and also a brand new one that I bought years ago.  That one cost me £50 which is why next time I needed one I rewound it instead of being ripped off by Sleeman and Hawkins

Mick

Alexdick

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Hi Alex, I`m thinking we have got a couple of the wires on the rectifier muddled up. Please see the documents and edited photos attached. Please also disconnect the two radio suppression condensers from the slip ring brush holders before doing your tests, as these can play havoc with the readings.

Bob

Bob

Can you tell me which numbers relate to what in the top box? The diagram is great but i don't know what is what! apologies for my ineptitude! many thanks
regards, alex

ajaffa1

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Hi Alex, I`ll try and add some more numbers and details to explain everything in the top box. I`ll also check what the resistances are so you can compare them with yours. Will try to post the results in the morning.

Bob

Alexdick

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Hi Bob
Thanks....I am looking for 1,2,3,4,5,6,7,8,13 and 18
Regards
Alex

ajaffa1

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No worries Alex, most of the numbers you mention are inside the generator, rather then the top box but I`ll edit the photos and post them in the morning.

Sorry it takes so long but I live about 11 hours out of sinc with Berkshire, UK. Hope you don`t have any major power outages while we are getting this sorted.

Bob

ajaffa1

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Hi Alex please see the attached photos (with numbers and arrows) I have also attach an edited wiring drawing having adding a few more numbers. Please note that I do not know which of two wires is connected to lugs 2 and 6 on the drawing. Please put your black probe on 1 and the red probe on 2 it should read 0.1 ohms if it does not please put the red probe on 6 it should read 0.1 ohms if it does. please swap the numbers on the drawing to reflect that 2 and 6 are reversed. (it makes no difference with alternating current).

The extra numbers on the drawing are not relevant at the moment, but could you please also the resistance between 1 and 19 ( black probe on 1, red probe on 19) should read 0.1 ohm

Bob

Alexdick

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Thanks Bob this is great. Sadly I wonít be able to do the test until the weekend but will get back to you as soon as I have done so! Thanks again. Alex

ajaffa1

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No worries Alex, get back to me when you can and hopefully we should be able to get her going again.

Bob