SW Efficiency/ PWM Angle Adjustment [RE-wrenches]

[Bill Brooks]

Sharkey,

You've got to watch out for sharks these days. What you say is ABSOLUTELY
FALSE! You just proved that I was correct.

Amps to the grid is NOT the measure of power flow. You are measuring the
flow of current, not power. Volt-amps only equal power when the power factor
is unity. Sign up for an electrical power class to learn about this stuff.
If you were to measure the power factor at 134 you would see that it was
atrocious. The reason the unit is inefficient is because you are sloshing
all this extra current around and not getting your meter to spin backwards
any faster.

Get a meter that shows true power flow and you will find that I am correct.
The measurements I made were done with a $10,000 BMI power analyzer that
will analyze the heck out of most electrical stuff.

I'm glad you responded and got involved after 4½ months, but don't shoot the
messenger. By the way, this is not official Trace information, and if you
want to live with 80% peak efficiency rather than 85-88%, just go right on
ahead. It won't hurt anything but your electric bill.

Electric Bill.


> -----Original Message-----
> From: Mr. Sharkey [mailto:sharkey at eugeneweb.com]
> Sent: Wednesday, September 05, 2001 8:19 PM
> To: RE-wrenches at topica.com
> Subject: SW Efficiency/ PWM Angle Adjustment [RE-wrenches]
>
>
>
> 	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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