On 7/9/2014 7:28 PM, Kim Elmore wrote:
Can ESR be related to DC leakage?
ESR is "equivalent series resistance" to an AC current. ESR will vary
with frequency. Here's are a couple of tutorials. fairly good
discussion of it. I think the second one is better.
http://www.low-esr.com/QT_LowESR.pdf
http://www.avnet-abacus.eu/news/technical-news/details/?tx_ttnews[tt_news]=1731&tx_ttnews[backPid]=2338&cHash=3ddf3975f083fbff1eadd89fd708e6f9
In terms of practical meaning, ESR is the component in the equivalent
circuit that tells us how much heat will be dissipated as a result of RF
current through the capacitor. If, for example, the capacitor is simply
bypassing a component to circuit common, it carries very little AC
current. But capacitors in the resonant parts of a power amplifier's
tank circuit, or in a bandpass filter in a contest station, are likely
to carry a lot of RF current.
When I first moved to CA in 2006, one of my first antennas was a
vertical for 160M that I loaded so that it was much longer than a
quarter wave. This made it inductive and with a series resistance of 50
ohms, so I used a series capacitor to tune out the inductance. I run
legal limit, so if the ESR is high, it's gonna fry. Here near Silicon
Valley, we are still blessed with a good electronics surplus warehouse,
so I grabbed a half dozen pieces each of 20-30 different capacitors that
looked like candidates. Prices are discounted to 5-10% of standard
costs, so I could afford to stock my junkbox.
I then took those caps, combined them to get the computed value for the
matching, and fired up the rig. Some of those caps got hot (and would
have smoked if I'd run them very long), others did not and are still
running fine 8 years later. The difference was ESR.
73, Jim K9YC
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