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While doing an investigation of distortion in my electrical utility power, I discovered a small contribution from my 15-yo grid-tie solar generator (consisting of three series-strings of seven Sharp NT-185U1 185-Watt panels per string, feeding a Sharp JH-3500U SunVista inverter). Neither the fifth-order distortion on the utility power nor the contribution from the SunVista inverter causes any problems. I am simply curious as to the causes. My post here is specifically to ask if anyone has enough knowledge of the SunVista product to tell me the frequency of its internal DC-to-AC conversion.
Both pictures below show the fifth-order distortion on the power line (upper trace) and a 300 Hz sine wave for comparison (lower trace). The distortion product is the output of an HP-330B Distortion Analyzer with the power line as an input (through a 6-Volt transformer for safety) and an HP-132A Dual Beam Oscilloscope for the display. The distortion from the local utility power supplier measures about 2% (2.5 Volts on my 125 VAC line). This distortion has a number of possible causes that I'll eventually track down; in the meantime it is causing no problem. The 300 Hz sine wave was added by me simply as an easy way to demonstrate that the distortion is fifth order for a 60 Hz electrical grid as we have here in North America. This distortion is commonly produced by motors, transformers, and AC-to-DC power supplies, common things out here in farm country. The causes may be in my home, a neighbor's home, or someone farther away but sharing our power line.
The lower picture shows the noise added by the SunVista solar inverter. It is roughly 0.4 Volt in magnitude and the frequency appears to be a few kilohertz (yes, I'm guessing). The amplitude is small enough that I can't separate it from the 300 Hz distortion product
Both pictures below show the fifth-order distortion on the power line (upper trace) and a 300 Hz sine wave for comparison (lower trace). The distortion product is the output of an HP-330B Distortion Analyzer with the power line as an input (through a 6-Volt transformer for safety) and an HP-132A Dual Beam Oscilloscope for the display. The distortion from the local utility power supplier measures about 2% (2.5 Volts on my 125 VAC line). This distortion has a number of possible causes that I'll eventually track down; in the meantime it is causing no problem. The 300 Hz sine wave was added by me simply as an easy way to demonstrate that the distortion is fifth order for a 60 Hz electrical grid as we have here in North America. This distortion is commonly produced by motors, transformers, and AC-to-DC power supplies, common things out here in farm country. The causes may be in my home, a neighbor's home, or someone farther away but sharing our power line.
The lower picture shows the noise added by the SunVista solar inverter. It is roughly 0.4 Volt in magnitude and the frequency appears to be a few kilohertz (yes, I'm guessing). The amplitude is small enough that I can't separate it from the 300 Hz distortion product