On 12/8/05, Brent Brown <brent.brown@clear.net.nz> wrote:
> Hi Russell,
>
> Use a cheap UPS?

Which has not a sinusoidal output but a DC one in the worst
circumstance and a square one in the best one.
I hope your power amplifier does not have transformers inside but
DC/DC converter...

cheers,
Vasile

 May have better regulation (repeat, may). Your
> generator, if it's the same one I'm thinking of, I think also has a 12VDC
> output, use it to charge the battery in the UPS. 425VA UPS is around
> US$67, or 660VA around US$76. Have thought of the same idea for keeping
> my UPS/PC running during longer power outages.
>
> Brent
>
> > 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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>
> --
> Brent Brown, Electronic Design Solutions
> 16 English Street, Hamilton 2001, New Zealand
> Ph: +64 7 849 0069
> Fax: +64 7 849 0071
> Cell/txt: 027 433 4069
> eMail:  brent.brown@clear.net.nz
>
>
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