by Kingcoal » Mon 05 Jun 2006, 17:36:53
$this->bbcode_second_pass_quote('', 'C')APACITOR LOSSES
Power loss in a capacitor may be attributed to dielectric hysteresis and dielectric leakage. Dielectric hysteresis may be defined as an effect in a dielectric material similar to the hysteresis found in a magnetic material. It is the result of changes in orientation of electron orbits in the dielectric because of the rapid reversals of the polarity of the line voltage. The amount of power loss due to dielectric hysteresis depends upon the type of dielectric used. A vacuum dielectric has the smallest power loss.
Dielectric leakage occurs in a capacitor as the result of LEAKAGE CURRENT through the dielectric. Normally it is assumed that the dielectric will effectively prevent the flow of current through the capacitor. Although the resistance of the dielectric is extremely high, a minute amount of current does flow. Ordinarily this current is so small that for all practical purposes it is ignored. However, if the leakage through the dielectric is abnormally high, there will be a rapid loss of charge and an overheating of the capacitor.
The power loss of a capacitor is determined by loss in the dielectric. If the loss is negligible and the capacitor returns the total charge to the circuit, it is considered to be a perfect capacitor with a power loss of zero.
I don't doubt that these guys can make a cap that can store lots of coulombs, however, I do doubt that they can and have the low losses required to be practical. High capacitance and low leakage tend to be inversely proportional.
In other words, the cap sits there and starts slowly discharging once the charging source is disconnected. This wouldn't be too practical for the guy who drives to the airport and returns a week later...
"That's the problem with mercy, kid... It just ain't professional" - Fast Eddie, The Color of Money