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--></style></head><body lang="EN-US" link="blue" vlink="purple"><div class="WordSection1"><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif"">Colleagues:</span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif""> </span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif"">In a recent post about some AC GFI tripping problems, I mentioned I am measuring some high THD readings in certain scenarios\u2014the highest being when the generator is charging at high percentages:</span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif""> </span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif"">Inverter only: 2.5% THD</span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif"">Gen Max: 19% THD</span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif"">Gen 5 Amps: 8% THD</span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif""> </span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif"">I measured the THD using a Fluke <a href="TJ3fTpspG2DGCzC">VR1710</a>. This is a handy little gizmo and pretty expensive considering its size. The device has limitations:</span></p><p class="MsoListParagraph" style="text-indent:-.25in;mso-list:l0 level1 lfo1"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif""><span style="mso-list:Ignore">1.<span style="font:7.0pt "Times New Roman""> </span></span></span><span style="font-size:12.0pt;font-family:"Verdana","sans-serif"">It is cord connected.</span></p><p class="MsoListParagraph" style="text-indent:-.25in;mso-list:l0 level1 lfo1"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif""><span style="mso-list:Ignore">2.<span style="font:7.0pt "Times New Roman""> </span></span></span><span style="font-size:12.0pt;font-family:"Verdana","sans-serif"">Results cannot be viewed in real-time.</span></p><p class="MsoListParagraph" style="text-indent:-.25in;mso-list:l0 level1 lfo1"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif""><span style="mso-list:Ignore">3.<span style="font:7.0pt "Times New Roman""> </span></span></span><span style="font-size:12.0pt;font-family:"Verdana","sans-serif"">It measures voltage parameters only.</span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif""> </span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif"">Here are my questions:</span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif""> </span></p><p class="MsoListParagraph" style="text-indent:-.25in;mso-list:l1 level1 lfo2"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif""><span style="mso-list:Ignore">1.<span style="font:7.0pt "Times New Roman""> </span></span></span><span style="font-size:12.0pt;font-family:"Verdana","sans-serif"">Has anyone here had to consider problems with high THD in any off-grid scenarios?</span></p><p class="MsoListParagraph" style="text-indent:-.25in;mso-list:l1 level1 lfo2"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif""><span style="mso-list:Ignore">2.<span style="font:7.0pt "Times New Roman""> </span></span></span><span style="font-size:12.0pt;font-family:"Verdana","sans-serif"">What readings are normal?</span></p><p class="MsoListParagraph" style="text-indent:-.25in;mso-list:l1 level1 lfo2"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif""><span style="mso-list:Ignore">3.<span style="font:7.0pt "Times New Roman""> </span></span></span><span style="font-size:12.0pt;font-family:"Verdana","sans-serif"">What is the significance of voltage harmonics versus current harmonics?</span></p><p class="MsoListParagraph" style="text-indent:-.25in;mso-list:l1 level1 lfo2"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif""><span style="mso-list:Ignore">4.<span style="font:7.0pt "Times New Roman""> </span></span></span><span style="font-size:12.0pt;font-family:"Verdana","sans-serif"">What instruments are you using to measure THD?</span></p><p class="MsoListParagraph" style="text-indent:-.25in;mso-list:l1 level1 lfo2"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif""><span style="mso-list:Ignore">5.<span style="font:7.0pt "Times New Roman""> </span></span></span><span style="font-size:12.0pt;font-family:"Verdana","sans-serif"">Has anyone seen high THD causing AC GFI tripping?</span></p><p class="MsoListParagraph" style="text-indent:-.25in;mso-list:l1 level1 lfo2"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif""><span style="mso-list:Ignore">6.<span style="font:7.0pt "Times New Roman""> </span></span></span><span style="font-size:12.0pt;font-family:"Verdana","sans-serif"">What other symptoms might occur with high THD?</span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif""> </span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif"">Tip: The reason we first started suspecting high THD is that cheap voltmeters registered abnormally high (including the onboard Radian metering) during periods of high THD, while true RMS meters (Fluke 87) continued to measure normal AC voltages. If you experience this situation, high THD is suspect.</span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif""> </span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif"">Answers are always gratefully appreciated.</span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif""> </span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif"">William Miller</span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif""> </span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif"">PS: If you are receiving a BCC of this email, it is because you are part of the team working on this problem. The message is directed to an industry forum in hopes of gleaning additional knowledge. I will share any results I receive.</span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif""> </span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif"">Wm</span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif""> </span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Arial","sans-serif"">Miller Solar</span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Arial","sans-serif"">17395 Oak Road, Atascadero, CA 93422</span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Arial","sans-serif"">805-438-5600</span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Arial","sans-serif""><a href="http://www.millersolar.com/">www.millersolar.com</a></span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Arial","sans-serif"">CA Lic. 773985</span></p><p class="MsoNormal"> </p></div></body></html>