rent imbalance and current waveform asymmetrical shape with
respect to the zero axis changes visibly, especially on Phase A current.
So, the quandary comes from Ohm’s Law, which states the
voltage is proportional to current times impedance, and Kirchhoff’s Law, which states the sum of the voltage drops around
a closed loop should equal zero. If the current level during the
0.25-second inrush during startup is reduced, so should the voltage drop in the source impedance, resulting in a less severe sag.
But scouring through the data for the last month and comparing
it to data recorded last year shows the same 10–12V sag, regardless of the solar panel output.
If the HVAC is provided with the same voltage level and has
the same impedance during startup and steady-state, the current levels should be the same. Somehow, in this case, the HVAC
impedance and the solar panel source impedance are in cahoots,
trying to disprove those trusted laws. Hopefully, more monitoring will provide more clues and help solve the mystery.
As a side note, the solar panels offset approximately 30 percent of the power over the two-week monitoring period. While
the panels are capable of providing 80 percent of the peak power
loading of the residence, they only do that starting at 9 a.m. and
tapering off around 7 p.m. The 11 a.m.– 6 p.m. peak solar output
doesn’t correspond with the peak power consumption in the residence, which occurs from 5 p.m.– 11 p.m. While the savings are
considerable, they are nowhere near break-even.
BIN GHA M, a contributing editor for power quality, can be reached
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