‰  NOW 25 WPM  ‰  TEXT IS FROM NOVEMBER 2012 QST  PAGE 65‰

CONDITION.  THIS IS REPEATED 60 TIMES PER SECOND.  THERE ARE THREE
IMPORTANT THINGS TO NOTE ONE IS THAT THE OUTPUT VOLTAGE WAVEFORM IS NOT A
PURE SINE WAVE, THE SECOND THING IS THE HOT AND NEUTRAL LEADS ARE NOT
SWITCHED AT THE SAME TIME.  THE THIRD THING IS THAT THERE IS LITTLE
DIFFERENCE BETWEEN THE HOT AND NEUTRAL LEADS, BOTH ARE ACTUALLY HOT AND
BOTH HAVE A LARGE COMMON MODE DC OFFSET IN ADDITION TO THE AC OUTPUT
VOLTAGE.  THE JOB OF A GFCI IS TO TRIP IF ANY OF THE CURRENT BEING SENT
DOWN THE HOT LEAD TO A LOAD IS NOT RETURNING BY THE NEUTRAL LEAD, BECAUSE
THIS MEANS THERE IS LEAKAGE SOMEWHERE, POSSIBLY THROUGH A PERSON.  EVEN IN
A HEALTHY POWER SYSTEM THERE IS ALWAYS SOME LEAKAGE CAUSED BY STRAY LINE TO
GROUND CAPACITANCE AND ANY COMPONENTS INTENTIONALLY INSTALLED BETWEEN LINE
AND GROUND, SUCH AS THOSE IN NOISE FILTERS AND SURGE PROTECTION.  WITH
COMMERCIAL POWER, THE SMALL VALUES OF LINE TO GROUND CAPACITANCE AND THE
‰  END OF 25 WPM TEXT  ‰  QST DE W1AW  ƒ