LR1 - Generator head scratching

[scott p]

Hey guys:

Just a cautionary note glort.  They make special inverter designed motors for a reason. Well-designed Mega Hz devices would probably work. Still, would be nice to have a have an oscilloscope. Old coils.

Sounds like a plan Jack, will be interesting to see what your final approach will be.

[sbkenn]

I have a similar one, but 3-phase.  It is inside-out, that is, the field is fixed, the 3-phase rotates.  It has severeal inductors for the exciter and regulation.  As mentioned in another thread, the mains comes through an inductor which saturates.  The exciter reference voltage is produced by a secondary winding on that inductor.  Sense inductor then (effectively) compares the reference voltage to the sensed voltage, rectifies it, and energises the field.
I am actively looking for a solid-state replacement as one of the sense windings is damages and I have to use phase-phase in order to get 230V out of the machine (one of the 3 sense inductors dead, means that ot is only supplying 2/3 of the normal current to the field.

[sbkenn]

Ran up with the AVR.
80 odd vdc into the stator to get 220 VAC.
Rotor 100 meg+

Insulation tester is a MeggER  ;-)
80VDC seems a lot.
Are you sure the polarity of the stator is correct, you could fighting the permanent part of the field. 
Alternatively, could the windings be for a 120V output ?

[Jack]

Megger, Megga.... hang onto the end of the cables and see what noise it makes.

The 80 vdc does seem quite high, particularly for no load.
Current thinking is that it may well be a 120 vac machine.
The exciter will only take current in one direction, so there must be a diode that I have not yet found.

The machine was previously running at 240 VAC, but with voltage drop to 180 VAC when loaded. This was before I got it, so I do not have details.
It is certainly well built. Insulation is in gre3at condition and if is turns out to be a 120 VAC machine, then the 240 vac running has not upset it.
When I ran it up initially there was no residual voltage to speak of. No problem flashing it though.

Further investigation is on hold awaiting new meters.

You should not have much trouble with the 3-phase AVR fitting. Plenty of voltage available. Provided your excitation current is below 10 amps, a $40 ebay job will do just fine. They even have free shipping.

cheers, Jack

[scott p]

Hey Jack:
I dug up a manual concerning generators similar to yours. There are several schematics of various builds.

If I am reading right your stater resistance is way too high.

These machines have a separate series winding, which is a built in starter. The shunt is I believe the exciter winding.They seem to work together.

I did not see a dedicated two slip ring 220 volt machine there but that doesn't mean there is no such animal.

Hey Jack:
I dug up a manual concerning generators similar to yours. There are several schematics of various builds.

If I am reading right your stater resistance is way too high.

These machines have a separate series winding, which is a built in starter. The shunt is I believe the exciter winding.They seem to work together.

I did not see a dedicated two slip ring 220 volt machine there but that doesn't mean there is no such animal.

Well I tried to send a PDF 4.3 megs deep but the server would not do it. Perhaps someone will enlighten me as to why.

[Jack]

Thanks Scott.
Is emailing it an option?
I will trap and PM you my address.

Cheers Jack.

[scott p]

Hey Jack:

Sure, we can try that.

[ajaffa1]

Hi Guys, been away from this forum for a while after the Australian bush fires burned my house down. I`ve read your posts and believe that all Lister generator heads of that era where supplied by Hawker Siddeley who acquired the Brush generator company.

The world expert on these is a guy called Lucian Nunes he can be found on the UK stationary engine forum, if he don`t know what it is and how to fix it you are in deep trouble.

Bob

[Jack]

Thanks Bob. Will see what I can find on Hawker to start with.