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Thread: Generator AVR

  1. #1
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    Default Generator AVR

    Perhaps more at home in "off topic" not sure so I flipped a coin.
    I put my hand up to have a look at a neighbors generator(old school, none of this inverter rubbish)
    8000W
    It's only outputting 120VAC.
    Freq is fine.
    Both seem stable(though it has just occurred to me to add more load)
    When running there is about 12VDC to the brushes and that seems to move about a little like the AVR is doing something.
    When I turn the motor off the DCV does increase to about 70VDC as the motor slows.
    I tried + and - 2 turns on the V trim pot and that seemed to do nothing.
    The AVRs seem pretty generic but I haven't been able to find out much about what the voltages typically should be. Just "if the V isn't right replace the AVR".
    They only run about $20(I cant find a "factory" one) and I have one on the way but thought I would ask if I am missing something.

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    Quote Originally Posted by Stustoys View Post
    none of this inverter rubbish
    Ooooh, I'm going to buy a Honda EU22i as soon as I can get my hands on one. I've been threatening to do it for years, but after the storms last week, I'm not going to tempt fate any longer.
    Chris

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    Seems I've found a question this forum can't answer! had to happen sooner or later I guess.

    Quote Originally Posted by jack620 View Post
    Ooooh, I'm going to buy a Honda EU22i as soon as I can get my hands on one. I've been threatening to do it for years, but after the storms last week, I'm not going to tempt fate any longer.
    Nothing against inverters. I have three, so far so good with them, not Hondas though, thats one of the reasons I have three lol
    We were without power for 3 days, so all three got a work out(helped a neighbor out with one). On the plus side I've finally found a way to tell when the power comes back on without walking out to the switchbox every hour, the spa isn't on the transfer switch so I can just plug a light into it.

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    I have absolutely no experience with the particular circuits but after a bit of reading it appears to me that the AVR is simply to maintain a stable voltage as load and revs of the engine change.

    Some articles suggest removing the AVR on a generator will result in unstable voltage outputs which is pretty logical but to only have half of the required output voltage ?
    I could be wrong but I do not believe the purpose of the AVR is to double the voltage just to keep it stable within a percentage of its intended output.

    Is the generator running at the correct revs ?
    Is it possible there are multiple windings in the generator to suit both main markets with the one design and one winding is short circuit ?

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    Quote Originally Posted by droog View Post
    I have absolutely no experience with the particular circuits but after a bit of reading it appears to me that the AVR is simply to maintain a stable voltage as load and revs of the engine change.
    Yes
    Quote Originally Posted by droog View Post
    Some articles suggest removing the AVR on a generator will result in unstable voltage outputs which is pretty logical but to only have half of the required output voltage ?
    I could be wrong but I do not believe the purpose of the AVR is to double the voltage just to keep it stable within a percentage of its intended output.
    As I understand it the AVR controls the VDC to the brushes(field windings) and thereby the output V. There is another winding that supplies the AVR with a reference V. So it's possible that reference V is incorrect and the AVR is just matching the output to the incorrect V. Sadly I can't find what these voltages should be. But my theory goes, if it is a bad reference V on a good AVR then adjusting the V trimmer pot should have changed the 120V a little(not saying I would be able to turn it up to 240V).

    Quote Originally Posted by droog View Post
    Is the generator running at the correct revs ?
    Yes the freq is controlled by the rpm. That side of things appears to be working fine, if you open the throttle by hand the freq goes up but quickly returns to 50Hz when left alone.

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    Yep agree with all the comments apart from I don’t believe there is a reference voltage, the reference is the output. To drive the AVR it is run via an exciter, probably a fixed magnet generator.

    See the diagram under “regulator circuit”
    Automatic Voltage Regulator (AVR) for Generators

    Also in this diagram there are two output windings both 120v. Are there multiple output windings and have you metered them ?

    On the other hand I may be completely off track.

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    Quote Originally Posted by droog View Post
    To drive the AVR it is run via an exciter, probably a fixed magnet generator.
    Well that makes far more sense. I was really wondering why they needed to generate a ref V why don't they just use a zener, turns out they do lol
    So really the V coming from the exciter likely isn't that important as long as there is "some there"?(which there is, I want to say 80ishV but I will have to check again)

    Quote Originally Posted by droog View Post
    Also in this diagram there are two output windings both 120v. Are there multiple output windings and have you metered them ?
    As I recall there is only one output winding but will check and get back to you tomorrow.

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    Quote Originally Posted by Stustoys View Post
    Well that makes far more sense. I was really wondering why they needed to generate a ref V why don't they just use a zener, turns out they do lol
    So really the V coming from the exciter likely isn't that important as long as there is "some there"?(which there is, I want to say 80ishV but I will have to check again)


    As I recall there is only one output winding but will check and get back to you tomorrow.

    Google AVR generator exciter voltage there is quite a bit of reading. Cant say how relevant voltages are to your particular unit but some suggestion you only need 5v excitation to start. Bit of info on EBS Excitation Boost Systems and outputs of around 20v. Also some Cummins documents with reference to over excitation fault protection of 67vdc.


    Good luck.

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    Quote Originally Posted by droog View Post
    Google AVR generator exciter voltage there is quite a bit of reading. Cant say how relevant voltages are to your particular unit but some suggestion you only need 5v excitation to start. Bit of info on EBS Excitation Boost Systems and outputs of around 20v. Also some Cummins documents with reference to over excitation fault protection of 67vdc.


    Good luck.
    Thanks
    They do seem pretty generic. I've not seen an AVR listing that mentions output V, only the kW rating. I wonder if all the alternators are wired the same even if they don't bring out the center point on 240V ones, other than to go to the AVR. Still will know more tomorrow.

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    Quote Originally Posted by Stustoys View Post
    Thanks
    They do seem pretty generic. I've not seen an AVR listing that mentions output V, only the kW rating. I wonder if all the alternators are wired the same even if they don't bring out the center point on 240V ones, other than to go to the AVR. Still will know more tomorrow.
    Last year on the basis they seemed generic. I put a honda one in a honda clone of about the same size. From memory it wasn't exactly plug compatible but with some at the time obvious mod it worked. It even had a potentiometer to adjust the output voltage. So my advice would be find one that looks similar and throw it in.

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    A lot of modern small single phase generators are 120/240v output. phase to phase is 240v and phase to neutral is 120v

    I wonder if someone had fiddled with the wiring.
    Gold, the colour of choice for the discerning person.

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    I did order one on the 2rd lamestlama, but it doesn't seem to have moved yet. Sometime before Christmas I'm sure.

    Couldn't rule that out RC but I'm struggling to see how you'd get this fault. I was told "it was working when we put it away last time, not working when we started it.". It does have a V meter so you would know straight away, though he did run his TV + a few other things on it for a fair while I believe. Going to go around and have more of a chat in the next couple of days.

    These measurements were done with a normal multimeter, in circuit with the exception of the four pin plug going to the AVR being unplugged. I've subtracted 0.04Ohm from the readings for the leads. Megger testing is an option but I think by that stage its junk?

    Two Blue wires going to the four in plug.
    0.79ohm between them and open circuit to everything else.

    Main winding 0.80ohm

    Black wire on the four pin plug
    0.17 to the white wire on the four pin plug
    0.09 to yellow main winding
    0.75 to red main winding

    White wire on four pin plug
    0.09 to yellow main winding
    0.86 to red main winding

    Unsurprisingly at this V everything open circuit to earth.

    When I first opened this up one of those bugs that build little mud nests what built one against the AVR. Looking into the stator Is that another nest or do they fill empty slots with goop that just happens to be the same color?
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    Quote Originally Posted by .RC. View Post
    I wonder if someone had fiddled with the wiring.
    Thinking about this some more.

    Wouldn't it be normal for earth to be bonded to neutral? Surely they aren't normally isolated?
    Now sure if plugged into a house it would bond them at the panel(I think), but I get the feeling that would be frowned upon.

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    Quote Originally Posted by Stustoys View Post
    Thinking about this some more.

    Wouldn't it be normal for earth to be bonded to neutral? Surely they aren't normally isolated?
    Now sure if plugged into a house it would bond them at the panel(I think), but I get the feeling that would be frowned upon.

    Not an electrician so will leave the details to someone that does know the specifics and details better than me but a lot of it has to do with what the generator is and how it is being used and connected.

    A bit of reading to start off:
    https://electricalconnection.com.au/...le-generators/

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    Not sure if this will help or not, but here's a couple of links regarding AVRs https://powerinsiderpro.com/3-sympto...n-a-generator/ and Check Your Portable Generator Output Safely (Using a Cheap Volt meter) (generatorgrid.com) . The alternators on generators also have diodes on their windings and it may be that a diode is blown and causing the problem, but at the same time I'm not sure what the diodes do. The diodes MUST be unsoldered from the generators for testing. I have two generators at work and one is a capacitor type and I'm not sure on the other, but they both only produce about 120 volts. So I'll be interested to know what you find.
    All The Best steran50 Stewart

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