Colleagues:
In a recent post about some AC GFI tripping problems, I mentioned I am measuring some high THD readings in certain scenarios—the highest being when the generator is charging at high percentages: Inverter only: 2.5% THD Gen Max: 19% THD Gen 5 Amps: 8% THD I measured the THD using a Fluke VR1710 <TJ3fTpspG2DGCzC>. This is a handy little gizmo and pretty expensive considering its size. The device has limitations: 1. It is cord connected. 2. Results cannot be viewed in real-time. 3. It measures voltage parameters only. Here are my questions: 1. Has anyone here had to consider problems with high THD in any off-grid scenarios? 2. What readings are normal? 3. What is the significance of voltage harmonics versus current harmonics? 4. What instruments are you using to measure THD? 5. Has anyone seen high THD causing AC GFI tripping? 6. What other symptoms might occur with high THD? 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. Answers are always gratefully appreciated. William Miller 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. Wm Miller Solar 17395 Oak Road, Atascadero, CA 93422 805-438-5600 www.millersolar.com CA Lic. 773985
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