<html><body><div style="color:#000; background-color:#fff; font-family:arial, helvetica, sans-serif;font-size:12pt"><div><span>I have found that many inverters will have a poor power factor when producing low power, and the power factor improves with load. if there are other things on your load it can effect the power factor./ <var id="yui-ie-cursor"></var> I have also seen very low power factor when motors run unloaded. I remember a gas dryer with no clothes and the power factor was 0.24</span></div><div>Power Factor is like a spring, a piece of equipment will draw current like compressing a spring and then send it back, so the utility has current flowing in the wires but no net work or no kWh </div><div>DT</div> <div style="font-family: arial, helvetica, sans-serif; font-size: 12pt;"> <div style="font-family: times new roman, new york, times, serif; font-size: 12pt;"> <div dir="ltr"> <font size="2" face="Arial"> <div
style="margin: 5px 0px; padding: 0px; border: 1px solid rgb(204, 204, 204); height: 0px; line-height: 0; font-size: 0px;" class="hr" contentEditable="false" readonly="true"></div> <b><span style="font-weight: bold;">From:</span></b> "toddcory@finestplanet.com" <toddcory@finestplanet.com><br> <b><span style="font-weight: bold;">To:</span></b> RE-wrenches <re-wrenches@lists.re-wrenches.org> <br> <b><span style="font-weight: bold;">Sent:</span></b> Monday, May 7, 2012 11:47 PM<br> <b><span style="font-weight: bold;">Subject:</span></b> Re: [RE-wrenches] power factor<br> </font> </div> <wbr>
<div id="yiv867354131"><font size="4" face="arial"><div style="margin: 0px; padding: 0px;">excellent replies to yes, a complicated issue. i think i finally understand this. thank you kent and dan!</div>
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<div style="margin: 0px; padding: 0px;">todd</div>
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<div style="margin: 0px; padding: 0px;">On Monday, May 7, 2012 9:02pm, "Exeltech" <exeltech@yahoo.com> said:<br><br></div>
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<td style="font: inherit; font-size-adjust: inherit; font-stretch: inherit;" vAlign="top">Hello Todd,<br><br>The short answer to your "is this a concern?" query, is "no".<br><br>Reactive power is one of the more complex aspects of electric power, and<br>certainly one of the most misunderstood. It can and does involve inductive<br>loads (e.g. motors), capacitive loads (e.g. some types of power supplies),<br>and non-linear loads (e.g. switch-mode power supplies, dimmers, etc.).<br><br>You likely know (or should know) "power factor" is the ratio of real power to<br>reactive power consumed by a load. Grid-tie inverters generate "real" watts,<br>which are then coupled to the grid. When a reactive load in your home is<br>consuming power, and you provide real watts to the load from the inverter,<br>this changes the ratio of real to apparent power consumed by the load as<br>seen by the utility company.<br><br>Dividing real power by apparent
power results in a unit-less value between 0<br>and 1 that describes this ratio.<br><br>Let's say a load in your home is consuming 1,200 real watts, and 1,250<br>apparent watts. This results in a power factor of 1200/1250, which equals<br>0.96. Pretty darn good.<br><br>Next, your grid-tie inverter provides 1,000 real watts back to the utility company,<br>which in turn is 1,000 real watts that the utility company no longer needs to<br>provide to the load described above. Thus the net "real" power consumed as<br>seen by the utility is now 1,200W - 1,000W = 200W.<br><br>This means they sell only 200 watts to power your load, but the "apparent"<br>power aspect is still there.<br><br>End result?<br><br>200 real watts / 1250 apparent watts yields a power factor of 0.160. Terrible by<br>any power company standards, yet you've removed 1,000 watts from the grid.<br>This is the value that will be displayed on your meter.<br><br>Efforts
are underway by EPRI and others to help create standards for future<br>generations of grid-tied inverters capable of generating "reactive" power (where<br>volts and amps are out of phase with each other) to help mitigate this effect.<br>I'm a member of the committee working toward that goal. (No, we're not there<br>yet. It'll take time.)<br><br>This is a very difficult topic to discuss and explain. Hopefully this helped.<br><br>Like Tom Cruise said at the end of "Top Gun" .. "It's complicated."<br><br><br>Dan<br><br><br><br>--- On <b>Mon, 5/7/12, toddcory@finestplanet.com <em><toddcory@finestplanet.com></em></b> wrote:<br>
<blockquote style="padding-left: 5px; margin-left: 5px; border-left-color: rgb(16, 16, 255); border-left-width: 2px; border-left-style: solid;"><br>From: toddcory@finestplanet.com <toddcory@finestplanet.com><br>Subject: [RE-wrenches] power factor<br>To: "RE-wrenches" <re-wrenches@lists.re-wrenches.org><br>Date: Monday, May 7, 2012, 9:46 PM<br><br>
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<blockquote style="margin: 0px 0px 0px 0.8ex; padding-left: 1ex; border-left-color: rgb(204, 204, 204); border-left-width: 1px; border-left-style: solid;" class="yiv867354131gmail_quote">wrenches,</blockquote>
<blockquote style="margin: 0px 0px 0px 0.8ex; padding-left: 1ex; border-left-color: rgb(204, 204, 204); border-left-width: 1px; border-left-style: solid;" class="yiv867354131gmail_quote"><br></blockquote>
<blockquote style="margin: 0px 0px 0px 0.8ex; padding-left: 1ex; border-left-color: rgb(204, 204, 204); border-left-width: 1px; border-left-style: solid;" class="yiv867354131gmail_quote">i have a question about my home's system. i was one of the first net metered systems in our area, so the utility company installed a fancy dual register meter which also displays kvar/power factor.</blockquote>
<blockquote style="margin: 0px 0px 0px 0.8ex; padding-left: 1ex; border-left-color: rgb(204, 204, 204); border-left-width: 1px; border-left-style: solid;" class="yiv867354131gmail_quote"><br></blockquote>
<blockquote style="margin: 0px 0px 0px 0.8ex; padding-left: 1ex; border-left-color: rgb(204, 204, 204); border-left-width: 1px; border-left-style: solid;" class="yiv867354131gmail_quote">when selling 1 kW today the power factor was .40 and the kvar was 2.37.</blockquote>
<blockquote style="margin: 0px 0px 0px 0.8ex; padding-left: 1ex; border-left-color: rgb(204, 204, 204); border-left-width: 1px; border-left-style: solid;" class="yiv867354131gmail_quote"><br></blockquote>
<blockquote style="margin: 0px 0px 0px 0.8ex; padding-left: 1ex; border-left-color: rgb(204, 204, 204); border-left-width: 1px; border-left-style: solid;" class="yiv867354131gmail_quote">this sounds horrible. <span style="font-size: 14pt;">question: is this a concern?</span></blockquote>
<blockquote style="margin: 0px 0px 0px 0.8ex; padding-left: 1ex; border-left-color: rgb(204, 204, 204); border-left-width: 1px; border-left-style: solid;" class="yiv867354131gmail_quote"><br></blockquote>
<blockquote style="margin: 0px 0px 0px 0.8ex; padding-left: 1ex; border-left-color: rgb(204, 204, 204); border-left-width: 1px; border-left-style: solid;" class="yiv867354131gmail_quote">todd</blockquote>
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