Plug packs: Difference between revisions

From OLPC
Jump to navigation Jump to search
Line 10: Line 10:
[[File:Chargerwaveform4.jpg]]
[[File:Chargerwaveform4.jpg]]


as above but run on battery power to 80% then plug in
as above but run on battery power down to 80% charge then plugged in




Line 25: Line 25:
[[File:Pcwaveform.jpg]]
[[File:Pcwaveform.jpg]]


For comparison a PC power supply. Vertical scale is 0.4A/square
For comparison a PC power supply. Vertical scale is 0.4A/square, the waveform has a wider pulse and could be expected to be less stressful on generators and transformers but not much better.


==Harmonics==
==Harmonics==

Revision as of 21:58, 4 December 2010

Waveforms

Charger input waveforms, 0.2A/square, screen edges and centre are the input voltage zero crossings


Chargerwaveform1.jpg

Green wallwart AD5953 ALF, XO1.5 running 93% charge 240V input


Chargerwaveform4.jpg

as above but run on battery power down to 80% charge then plugged in


Chargerwaveform2.jpg

Green wallwart Delta ADP17FBA, XO1.5 running 93% charge 240V input


Chargerwaveform3.jpg

White wallwart Bestek NA0241WAA, XO1.5 running 93% charge 240V input


Pcwaveform.jpg

For comparison a PC power supply. Vertical scale is 0.4A/square, the waveform has a wider pulse and could be expected to be less stressful on generators and transformers but not much better.

Harmonics

The load is well balanced with respect to leading/lagging power factor, showing only a slight leading or capacitive power factor. The waveform is very rich in harmonics. This could lead to overheating in transformers and generators due to eddy currents.

A harmonic analysis on the following approximation of the waveform

Assumed waveform.jpg

yielded this result

Fourier analysis.jpg

File:Plugpack harmonics.xls

Refs

http://www.idc-online.com/technical_references/pdfs/electrical_engineering/Generators_and_nonlinear_loads.pdf

http://sureshks.netfirms.com/article/upsgen/upsgen.htm