SV: RE: [sdiy] Multiple Voltage Power Supply / design problem!

[karl dalen]

Soon that flatness will become DC mains! :-)

KD

--- harrybissell at copper.net skrev:

>  Paul wrote:
> >>By the way, anyone looked at a scope trace of the mains lately? It
> isn't a sine wave any more, more like the Matterhorn with the tip
> chopped
> off, thanks to all the switch mode supplies hanging off it. Oh, and I
> wonder where those mains frequency spikes come from??
> 
> 
> Amen from the choir. I work on welding busses... and with the new
> inverter
> welders (think 800KW switcher :^) we can totally flat top a sine wave.
> 
> All the FWB rectifiers take current at the peak of the sine wave.
> 
> One idiot company did a 'power line analysis' for a customer of ours.
> They
> reported the bus was OK because the voltage drop was only 50V max.
> They did 
> ~not~ notice it was 50V and as flat as an airfield. We were losing
> diode
> modules left and right as they turned on-off MANY times each half
> cycle
> and died of reverse recovery losses.  SAME idiots said we had 300%
> harmonic
> distortion in neutral.  That was based on a Wye bus, with a nominal
> ONE AMP
> at rest, and a whole THREE AMPS when our equipment was running. All
> the current was from capacitor noise snubbers... and the idiots did
> not notice they had failed to ground ANY of the controls (which would
> have given that
> current a kinder, gentler path :^)
> 
> I'm probably making those mains spikes as well, but if they are
> reaching 
> Australia there is a big problem :^P
> 
> /rant
> 
> H^) harry
> 
> 
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