PSN-L Email List Message

Subject: Re: inverters
From: ChrisAtUpw@.......
Date: Tue, 11 Jul 2000 22:33:01 EDT

In a message dated 11/07/00 19:48:48 GMT Daylight Time, sean@........... 

> I am concerned about the bad rap being laid on inverters to provide
> uninterruptible and possibly precision AC power.   
> As with any device, there are good designs and there are boxes of
> compromises that can cause problems. 

    We may not all know what to look for in the advertising blurb and some 
manufacturers seem very silent about minor details like waveforms and 
frequency stability. When does 'modified sine wave' = troublesome square wave 
of no discernable stability or power?
> As always, the good, the bad, and the ugly of it is that you get what 
> you pay for, so a good initial investment is worth considering.
> And as with any power switching device, a good design does include proper
> transient suppression and shielding/grounding. Surprisingly, a significant
> radiator of noise are the DC input cables, which often are not by-passed
> with capacitors and isolated with toroid inductors.

    Yup. My experience:- The shiny new box with brightly coloured knobs is 
clearly labelled 'no user servicable parts inside' and comes without a 
circuit diagram. This is 'confidential information' according to the 
salesperson, who seems to take the production of an adjustable spanner and a 
cross head screwdriver as a mortal insult.....  

> I have consistently used inverters to power seismic systems....,
> These are of the totally uninterruptible design, without any switching
> to the inverter in the event of an outage: the loads operate continuously 
> from the 1 kilowatt precision inverters, which operate on either
> 12 or 24 Volt, 200 or 100 ampere supplies.....

    Which might cause the love of my life to make some very terminal 
remarks..... Is there a well suppressed, crystal controlled, sine wave 
inverter / charger unit of ~200 W continuous rating that won't make a 
glaringly obvious hole in my monthly paycheck, please?



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Larry Cochrane <cochrane@..............>