Sunday, May 27, 2007 at 16:05
>I have used an ALDI $100 special for powering a laptop, a
>microwave, lighting and various appliances… and the only
>appliance that acted weirdly was a vacuum cleaner (explain
>that one Harding!!)
G’Day Fawlty
I’m glad you asked that question because this is an issue with square wave
inverters which is little understood and the subject of much confusion – even in the scientific community, I might add!
Now, as you will know Fawlty, small vacuum cleaners (in common with a few other similar appliances) utilise a shunt wound, series/parallel universal motor, often with capacitive power factor correction and herein lies the problem: because the windings (field and armature) of these motors must be very tightly wound over a mu metal magnetic shield (due to space and heat dissipation issues) it creates very sharp angles in the copper wire of the winding. Normally this is not an issue because a 240V sine wave supply only changes at a, comparatively, slow rate however a square wave inverter (as it’s name suggests) has very rapid rates of change when the waveform reaches, and descends from, peak voltage – we’re approaching the nub of the science now – and with the more recent MOSFET switching technology which is _very_ fast does not allow time for electron progression in the windings (due to the sharpness of the bends – which is why some cleaners will work but others won’t – manufacturing tolerances). This is where real problems may develop: normally it won’t be an issue, there will simply be a build up of electrons in the negative polarity which will cause a high voltage to develop at the MOSFET and possibly blow a fuse. (Electron flow is from negative to positive, obvious really). HOWEVER it has been observed that in rare instances where the MOSFETs have received an unusually high level of ‘n’ channel doping (manufacturing flaw) a situation has developed causing electron discharge into the local atmosphere; again this is usually safe enough but there is a (albeit small) risk that in an environment which uses ionising smoke detectors utilising Strontium 4 as the detecting element the excess electron cloud could result in a chain reaction causing a cold fusion process to commence. Although this would be invisible to individuals the EMP pulse generated could
well destroy any electronic equipment in the near vicinity (and males of a reproductive inclination should be cautious too!) .
freeenergynews.com/Directory/ColdFusion/
As I say: not a lightly occurrence but please be wary of vacuum cleaners and square wave
inverters.
Thanks again for raising this Fawlty.
Mike Harding
mike_harding@fastmail.fm
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