<html><head></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; ">Once again Dan, you nail great information to this board. Key phrase: "used within its specification" <div><br></div><div>Back in the '80's I replaced hundreds of small caps in very poorly designed 2-3 year old C-band satellite receivers, all damaged by excessive internal heat.</div><div><br></div><div>Thanks for your input.<br><div>
<span class="Apple-style-span" style="border-collapse: separate; color: rgb(0, 0, 0); font-family: Helvetica; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-align: -webkit-auto; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; font-size: medium; "><span class="Apple-style-span" style="border-collapse: separate; color: rgb(0, 0, 0); font-family: Helvetica; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; font-size: medium; "><span class="Apple-style-span" style="border-collapse: separate; color: rgb(0, 0, 0); font-family: Helvetica; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; font-size: medium; "><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><div><br class="Apple-interchange-newline">Larry Crutcher</div><div>Starlight Solar Power Systems</div></div></span></span><div><br></div></span></div><div><br class="webkit-block-placeholder"></div><div><br></div><div><div>On Jan 12, 2012, at 4:59 PM, Exeltech wrote:</div><br class="Apple-interchange-newline"><table cellspacing="0" cellpadding="0" border="0" style="position: static; z-index: auto; "><tbody><tr><td valign="top" style="font: inherit;">Wrenches,<br><br>I wish this urban myth about electrolytic capacitors would<br>die, but it won't. It's been a wonderful marketing ploy for<br>some time now.<br><br>Simply stated, existence of electrolytic capacitors in inverters<br>does NOT mean the inverters are less reliable. Satellites<br>have been using electrolytic caps for decades, and look<br>how long THEY last! (I know, because I've helped to design<br>power supplies for aerospace applications.)<br><br>What it boils down to is this: if a quality electrolytic capacitor<br>is used within its specifications, you can expect 60+ years<br>of life from it in an inverter application. Conversely, if a<br>circuit is poorly designed, you can ruin any electronic part<br>in a very short time.<br><br>What defines capacitor "life"? It's defined as the doubling<br>of the internal effective
series resistance of the capacitor<br>from the value it had when it (the cap) was new.<br><br>This is energy lost. It also causes the capacitor to operate<br>at a slightly higher internal temperature than when it was<br>new (all other factors being the same).<br><br>Result? It all depends on how the circuit is designed. In<br>our case, the inverter efficiency decreases approximately<br>a quarter to one half of a percent. The waveform distortion<br>also increases, but it takes lab grade equipment to detect<br>the change. If you're worried about a 1/2 percent drop in<br>the inverter efficiency, your concern is misplaced. After all,<br>PV degrades over time much more than that!<br><br>So why the bad rap on capacitors?<br><br>Like tires, they DO wear out. 40 years ago, "premium"<br>tires were rated for 30,000 miles. Could you wear them<br>out in less? Absolutely! Drive like a 16 year old kid
with<br>a muscle car, and it's easy. On the other hand, I just bought<br>a new set of tires. The old ones still had tread, but at 88,000<br>miles, they'd seen their better days. This is a far cry from 30k<br>mile tires.<br><br>Capacitors have progressed in the same manner. A long time<br>ago, capacitors wore out in 5 to 10 years. Today, it's an entirely<br>different story.<br><br>As long as the circuits in which the electrolytic capacitors are<br>used are well designed, you have nothing to worry about.<br>Electrolytic capacitors in a well-designed application will outlive<br>all of us.<br><br><br>Dan Lepinski<br>Senior Engineer<br>Exeltech<br><br><br></td></tr></tbody></table></div></div></body></html>