genoraters

Discussion in 'Tech/Mech General' started by francour, May 2, 2012.

  1. francour

    francour Read Only Funster

    Joined:
    Mar 13, 2012
    Messages:
    94
    Likes Received:
    13
    Location:
    Pontefract
    Hi all just reading about using a genny with a m/h whats the problem i would like to no more any answers please:helpsos: Thanks Bernie
     
  2. Reallyretired

    Reallyretired Funster

    Joined:
    Apr 27, 2008
    Messages:
    5,706
    Likes Received:
    3,211
    Location:
    Eastbourne East Sussex
    I would suggest you do a search on the forum as many words have been written about generators.
     
  3. TheBig1

    TheBig1 Funster Life Member

    Joined:
    Nov 27, 2011
    Messages:
    7,222
    Likes Received:
    9,602
    Location:
    Dorset
    in short..... cheap unregulated generators and expensive electronics in motorhomes dont mix well. the really basic generators are known to send out voltage spikes and variations. These spikes and variations terminally damage the mains to 12v system and battery charger. the cost of such repairs would of bought a decent generator in the first place, plus parts for some systems take ages to get hold of making using the van difficult

    tried to keep it basic for all to understand, but can offer a more technical based reply if needed:thumb:
     
  4. vwalan

    vwalan Funster

    Joined:
    Sep 23, 2008
    Messages:
    7,594
    Likes Received:
    3,853
    Location:
    roche cornwall
    solar+
     
  5. pappajohn

    pappajohn Funster Life Member

    Joined:
    Aug 26, 2007
    Messages:
    29,466
    Likes Received:
    16,913
    Location:
    YO11 2BD
    in general terms......

    a generator with a pure sinewave (inverter genny) is very smooth and flowing and is the same as in your house supply and can run anything electrical.

    a generator with a square wave (cheap 2 stroke or open framed genny) will be ok for heating elements etc but motors and electronics (computers and charge controllers etc) cant tolerate the sudden, sharp change in wave direction.

    in the attached pic,
    the sine wave is a smooth transitional curve from one peak to the next.
    the square wave is a sudden change between peaks
     

    Attached Files:

    • Like Like x 1
  6. Reallyretired

    Reallyretired Funster

    Joined:
    Apr 27, 2008
    Messages:
    5,706
    Likes Received:
    3,211
    Location:
    Eastbourne East Sussex
    Realising you are something of an expert, I hesitate to question you but surely a cheap genny (no inverter) will always produce a pure sine wave as it is coming direct from a mainbs voltage alternator. You will only get a square wave from a cheap inverter.

    Incidentally as I found by experiment, a cheap 500w inverter (modified square wave) runs the motors in the little twin tub washing machine with no problems, and a bigger one will quite happily run a hairdryer, so not necessary to have a pure sine wave for all motors.

    I agree it is the mains spikes that may damage the van charger using a cheap genny, but not because they produce a square wave.
     
  7. pappajohn

    pappajohn Funster Life Member

    Joined:
    Aug 26, 2007
    Messages:
    29,466
    Likes Received:
    16,913
    Location:
    YO11 2BD
    I'm no expert by any means but i do research a subject i have an interest in.

    a cheap (non-inverter) or site genny will only produce a square wave form, and an inverter can alter this electronically to a modified square wave or pure wave.
    a cheap genny isn't sophisticated enough to do this.

    mains grid electric goes through various processes before it gets to your house.

    a square wave genny running an electronic appliance will produce 20% to 30% more heat within the appliances componants than a pure sine wave due to the way the wave is formed .

    heat kills the appliance, a well know phenomenon in the demise of onboard chargers..... not always the voltage spikes
     
  8. Hayleylulu

    Hayleylulu

    Joined:
    Feb 17, 2008
    Messages:
    5,392
    Likes Received:
    3,889
    Location:
    Full timing in the van
    Get a good noisy one keeps the moaners away from you
     
    • Like Like x 3
  9. Snowbird

    Snowbird Funster Life Member

    Joined:
    Apr 24, 2009
    Messages:
    10,141
    Likes Received:
    16,390
    Location:
    Liverpool.
    aaaaaaaaaaaaaaaah....no problems with spikes with me windmill and solar panels.

    No noise and I dont have to carry smelly petrol around either :Rofl1:

    As a bonus nobody knows were am wilding, cos they cant hear me.
     
  10. vwalan

    vwalan Funster

    Joined:
    Sep 23, 2008
    Messages:
    7,594
    Likes Received:
    3,853
    Location:
    roche cornwall
    i,m with dave here . i never get to have ehu when away .
    do have a big diesel genny on board for if i need to use a welder.
    solar works for me.
    and at the moment is still running my fridge in the house . extension lead from inverter through windows into kitchen . makes sense to me . also use vacum with it in a morning .
    i think many should think hard about what they really need that uses so much power.
    in all my m,homing days this is the first time i have had ehu fitted to a camper and havent used it yet. they tell me you have to go on campsites . must be why. ha ha :thumb:
    and in winter i get the best output from my panels . bet dave did last winter.
     
  11. JeanLuc

    JeanLuc Funster

    Joined:
    Nov 17, 2008
    Messages:
    2,782
    Likes Received:
    1,857
    Location:
    Warwickshire
    It is rather more complicated than what wave form the generator delivers when free-running. The wave form is affected by the type of load applied to it. So even though a cheap generator may appear to deliver a decent wave form, it cannot cope with difficult loads. Furthermore, as previously stated, cheap generators are poorly regulated, making them prone to deliver spikes and surges. These can be very damaging.

    There is a paper by Sterling Power Products explaining some of the issues. Charles Sterling is an expert - I am not, but have read the literature.

    Click this link then scroll to the bottom to the section titled 'Other Technical Information'. The paper is called 'Why spend more on a small generator?'
    http://www.sterling-power.com/downloads.htm
     
  12. hilldweller

    hilldweller Funster Life Member

    Joined:
    Dec 5, 2008
    Messages:
    26,432
    Likes Received:
    25,110
    Location:
    Macclesfield
    Sorry John but I'll believe it if you can show me proof. I can bring a battery scope to a meet if you like.

    I think you are confusing inverters here.

    I believe el cheapo generator will produce a sine wave but frequency and voltage will be very variable which is highly undesirable for electronic equipment.

    I also believe that the so called pure sine wave inverters or gennies are a lie and are in reality a digitally synthesised sine way close to a pure sine wave. I've got a good "pure sine wave" 300W inverter, I'll scope it tomorrow and report.
     
    • Like Like x 2
  13. pappajohn

    pappajohn Funster Life Member

    Joined:
    Aug 26, 2007
    Messages:
    29,466
    Likes Received:
    16,913
    Location:
    YO11 2BD
    Until i find reliable proof otherwise i stand corrected Brian.
     
  14. pappajohn

    pappajohn Funster Life Member

    Joined:
    Aug 26, 2007
    Messages:
    29,466
    Likes Received:
    16,913
    Location:
    YO11 2BD


    Brian, I stand corrected and humbled by your superior knowledge :Blush::Laughing:

    first picture is from a cheap non-inverter genny...still a very rough waveform

    second is from a Honda inverter 2kv.

    third is from a cheaper inverter genny
     

    Attached Files:

    • Like Like x 2
  15. hilldweller

    hilldweller Funster Life Member

    Joined:
    Dec 5, 2008
    Messages:
    26,432
    Likes Received:
    25,110
    Location:
    Macclesfield
    The 3rd one you can see the synthesizer frequency. about 1600Hz.
    The Honda, awesome.

    I'll scope my inverter tomorrow, try and find some nasty loads for it.
     
    • Like Like x 1
  16. aba

    aba

    Joined:
    Oct 27, 2009
    Messages:
    2,793
    Likes Received:
    1,119
    Location:
    yorkshire
    just out of interest could you scope the mains coming into your house as a bench mark
     
  17. TheBig1

    TheBig1 Funster Life Member

    Joined:
    Nov 27, 2011
    Messages:
    7,222
    Likes Received:
    9,602
    Location:
    Dorset
    now that is interesting you ask this question. power distribution in this country is fairly uniform voltage wise, but you will always see noise on the waveform. until recently this could clearly be seen as an issue in distribution. however these days there is broadcast over power lines (internet and tv) being trialled in some areas and of course some consumer items that send a signal down power lines. one of the biggest issues holding back powerline broadcast is the signal to noise ratio introduced by transformers at sub stations and other pieces of equipment. therefore its not guaranteed that you will get a perfect sine wave by scoping the distribution phase
     
  18. Gromett

    Gromett Funster

    Joined:
    Feb 27, 2011
    Messages:
    7,939
    Likes Received:
    13,998
    Location:
    UK
    Just a couple of quick questions/points....

    A square wave will throw off loads of harmonics as well. This will cause problems for any device that is RF sensitive. A pure sine wave has no harmonics. If any of you play an electric guitar you know what 50Hz mains hum sounds like when it gets into your amp. Imagine all the harmonics of 50Hz going in as well. Doesn't do much for the sound quality.

    The lumps in the waveform for the cheap genny are not square waves. I would guess this is where the brushes are passing over defects. In more expensive generators I would also guess they use brushless alternators.

    Theoretically any rotating generator describes a sine wave and the output of the generator should be roughly sinusoidal allowing for manufacturing defects or inconsistent materials.

    On of the beauties of a pure sine inverter based generator is that the output can be modified to allow for loads. Noisy loads will feed this noise back into the generator amplifying any inconsistencies. The power factor of the load will also affect the quality of the power. With an inverter based generator these can be better managed.

    Non mechanical inductive loads are likely to be worst affected by pseudo sine inverters. Things like tooth brush chargers where there is no rotating part to smooth out the load. Here you are running into inductive reactance that isn't smoothed by the mechanical motion of a motor such as in a washing machine.

    Things like switch mode power supplies or for that matter any device that relies on pulse width modulation may have problems also.

    Some devices that use a phase locked loop that is triggered at the top of the wave form and requires consistent frequency to operate may have troubles but I can't stretch my brain far enough at this time of the morning to think of an example that is used in a motorhome...

    I agree with the heat problems mentioned by Pappajohn (not sure what he means by square wave generators though) but there are also other mechanical issues that can cause failure.

    All the above is based on my training from almost 20 years ago so I apologise if my memory has let me down on anything:Doh:
     
  19. Gromett

    Gromett Funster

    Joined:
    Feb 27, 2011
    Messages:
    7,939
    Likes Received:
    13,998
    Location:
    UK
    Just thought I would do a quick search for a drawing that show what I mean when I said
    As I don't think I explained myself very well.

    I found this on google images :BigGrin:

    [​IMG]

    Thank you wikipedia, why didn't I think to look there first.:thumb:
     
    • Like Like x 1
  20. hilldweller

    hilldweller Funster Life Member

    Joined:
    Dec 5, 2008
    Messages:
    26,432
    Likes Received:
    25,110
    Location:
    Macclesfield
    A quick look......

    Sterling 300W sine wave.

    1 my jaw dropped, perfect sine wave.

    2 Plug in laptop charger, very slight distortion.

    El Cheapo 150W

    3 As rough as it gets

    4 With load see how it has increased the pulse width.

    The laptop was charging OK on that square wave, but it's a beefy power supply, I'd not risk a little phone charger on it.
     

    Attached Files:

    • i1.jpg
      i1.jpg
      File size:
      94.8 KB
      Views:
      6
    • i2.jpg
      i2.jpg
      File size:
      95.2 KB
      Views:
      5
    • i3.jpg
      i3.jpg
      File size:
      35 KB
      Views:
      5
    • i4.jpg
      i4.jpg
      File size:
      34 KB
      Views:
      5
    • Like Like x 1

Share This Page