If you'll pray, He will answer you the same as me:
- I can help you if you'll help yourself.

There is a cheap alternative you didn't mention it:
- use a feroresonant stabiliser after your mains generator. Is able to
stabilise from 180 to 240V (european style) at up to 5KW. You should
found such stabiliser on any second hand rubish store.

Vasile


On 12/8/05, Russell McMahon <apptech@paradise.net.nz> wrote:
> I can and will try this for myself but, as I need the result in 48
> hours time I'll also ask here. Someone should have invented this wheel
> already.
>
> I have an exceedingly cheap and cheerful petrol motor powered
> alternator rated at about 700 watts max. (Cost about $US65 new).
>
> Voltage stability at constant load is "OK" but if you step-change the
> load it surges extremely badly. Variation is enough for incandescent
> bulbs to dim badly and/or get VERY bright for a second or so. I
> measured the surges a while ago but don't recall the results - very
> nasty is enough to know. Some loads don't mind this while others would
> die.
>
> I need to run a PA system and bass guitar amplifier for a concert 48
> hours from now. Required wattage is liable to be under 100 watts.
>
> I could:
>
> 1 - Pray
>
> 2 - Add a large swamping load first and try to ensure nobody step
> changes the load.
>
> 3 - Add a manually multi step switched load and use this to phase in
> and out real loads. Actually quite easy to do.
>
> 4 - Make an electronic stabiliser - eg smoothly winds in a large
> resistive load, then step adds true load and matches it by dropping
> off resistance and then slowly winds off most of the DC load. Could do
> this only when load is added or removed at known points or leave some
> resistor load in to allow auto action to handle step changes along the
> way.
>
> 5 - Add a "spinner" - an unloaded motor which acts as a rotary
> capacitor.
>
> 6.    Use a DC/AC converter - with a lead acid battery charged by the
> alternator (if needed)
>
> 7- Some combination (especially 1 :-) ).
>
> ______
>
> 1.    On an 'as required' basis.
> 2.    Should be effective with vigilance.
> 3.    Is easyish and effectiveish.
> 4.    is not hard and arguably the best long term solution BUT there's
> too much else to do unless it's essential to do it this way,.
> 5    I'm not sure how well this works on 1 phase due to the quasi
> rotating field compared with 3 phase.
> 6    Cheating. Probably easiest at the power level concerned.
>
> Thoughts ?
>
>
>        Russell McMahon
>
>
>
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