SW Efficiency/ PWM Angle Adjustment [RE-wrenches]

[Mr. Sharkey]

	OK all you Wrenches, I've kept quiet here for about 4½ months, but I have
to weigh in on this subject of altering your tech menu settings in the name
of "efficiency". After reading Bill Brooks' post about changing the PWM
Angle value from 129° to 126°, I went straight out to my SW2512 and made
the adjustment. Today at noon, I put an amp-clamp on the AC line and took
some readings. The amperage at 126° was at least 1½ to 2 amps *lower* than
the reading at the default 129° !!! Running the value up to 134° (maximum)
gave me almost another amp of AC current over the default setting.
	I don't know how you guys measure efficiency, but I read it as more amps
back into the utility with a fixed PV current and voltage. Could it be that
the Trace advice to lower the phase angle was designed to lower the output
of the inverter's intertie current, and by effect, lower the operating
temperature? Have any of you (regularly) checked AC backfeed amps with
anything more accurate than the built-in SW metering?
	Somebody want to venture a guess what's going on? I had a lengthy
discussion with Darren Emmons about SW inverters and the power factor the
inverter sees when in intertie mode. Does the PWM Phase Angle compensate
for PF, which would make the setting unique for each installation?
	At any rate, I'd caution each of you not to assume that altering the PWM
Phase Angle setting will automatically change your efficiency for the
better. Put a clamp on that AC line and see what really works.

	-S

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