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Author Topic: AVR?  (Read 772 times)

Jordan

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AVR?
« on: March 01, 2019, 08:03:54 AM »
I have an old Markon model LC28D.
I took covers off to have a look, and saw brushes, slip rings, wound stator and rotor.
Also there was a big coil (choke?) mounted on the frame, and some diodes and two adjustable wound resistors.
What wasn't obvious was a regulator.
Is it normal for this alternator not to use a regulator?
Would the addition of an Automatic Voltage Regulator be beneficial?

ajaffa1

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Re: AVR?
« Reply #1 on: March 01, 2019, 11:30:49 AM »
Hi Jordan, older generators did not have AVR`s as the technology had not been invented, they usually run a field winding fed with DC electricity to produce a North/South magnetic field in which the stator rotates. The DC is normally created by feeding some of the AC generated through diodes or rectifiers to produce DC. This is not a very smooth Dc so it is common to try to smooth it using chokes or capacitors. There are so many variations it is hard to guess at what you have, a couple of photos might help.

Bob

mike90045

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Re: AVR?
« Reply #2 on: March 01, 2019, 03:06:40 PM »
Does it currently function at all ?

The saving grace is, it does not use a capacitor, which often fails with age (20+ years).  Chokes are really just a rotor winding that does not spin (copper coil on iron core).  unless a critter chews and pees on them and ruins the insulation, they last as long as the insulation does.

BruceM

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Re: AVR?
« Reply #3 on: March 01, 2019, 05:38:23 PM »
If you aren't satisfied with the original regulation, you can certainly add a brushed AVR as long as you educate yourself on the genset, rotor and stator configuration. 

If you can find or create a wiring diagram, we can certainly help you figure out how to connect an AVR.  The AVR is typically just an AC interrupter; the excitation for the field coils is chopped so that the desired output AC level is maintained.  After the AVR, the chopped AC is rectified into a lumpy DC. The field coils have so much inductance (which acts as a choke to smooth the current) that clean DC isn't needed.

You may find that the original regulation scheme is adequate; it was designed to be so.


Jordan

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Re: AVR?
« Reply #4 on: March 03, 2019, 08:47:33 AM »
Thank you Bob, Mike & Bruce.

I discovered there are also 2 capacitors tucked under the choke.
I put photos here, hope they can be seen: https://postimg.cc/gallery/t4rzxeoq/

I'm happy not to use an AVR if it works OK without one. They are surprisingly expensive.
As they have no battery to charge, it's a mystery to me what they do.

I found a manual, but it's of the type that has several wiring diagram variations, all confusing.
Good news is that there's an old guy lives nearby who used to rewind all sorts of electric machines, who came over to check it out.
He took some coil resistance readings and says it's good prospect, so I will now make up mounts for it, and organise the belt transmission from my Lister CS1.

Jordan

ajaffa1

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Re: AVR?
« Reply #5 on: March 03, 2019, 08:38:52 PM »
Hi Jordan, well done, that looks to be a very robust unit. If I can give you one piece of advice it is this: take out the two electrolytic condensers and write down what it says on them (micro farads and voltage), keep the information somewhere safe. These have a bad habit of failing in spectacular fashion which often makes the writing on them illegible, trying to replace them and get the voltage regulation right by trial and error is a pain in the ass!

Bob

Jordan

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Re: AVR?
« Reply #6 on: March 04, 2019, 05:54:18 AM »
Good idea, Bob.
I'll do that.

glort

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Re: AVR?
« Reply #7 on: March 04, 2019, 11:12:06 AM »

I learned to either engrave things or write under covers etc on the unit itself.
Lawnmower has filter, blade and belt numbers under the Bonnet, septic pump has parts kit ( and a spare kit) under the enclosure. Mig Welder has tip numbers written under the cover and so Does plasma although after the difficults of getting consumables last time, I ordered a life time supply now.

If I loose the lists, then I won't be needing the parts anyway! :laugh:

Jordan

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Re: AVR?
« Reply #8 on: March 05, 2019, 10:23:52 AM »
We think alike, Glort.
Permanent markers are my friends.
I use them everywhere, even at work.
It's hard for people to critisize, because the benefits of locally accessible info are obvious.