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How could a pulse cap operate in TC?
- To: tesla@xxxxxxxxxx
- Subject: How could a pulse cap operate in TC?
- From: "Tesla list" <tesla@xxxxxxxxxx>
- Date: Sun, 17 Jul 2005 12:07:59 -0600
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Original poster: father dest <dest@xxxxxxxxxxx>
hi Steve, Gerry.
> Original poster: Steve Conner <steve@xxxxxxxxxxxx>
> At 12:36 15/07/05 -0600, you wrote:
>>correct me where i`m mistaken.
> You're getting I2R losses (due to RMS current) confused with dielectric
> losses (due to RMS voltage)
no - i only wanted to say, that the definite Irms corresponds to the
definite power of dielectric loses. it would be different on
differerent frequencies, and at some frequency this power _itself_ could
exceed the limit of maximum power dissipation for the cap.
or _at this frequency_ the sum of power of dielectric loses and resistive
loses would exceed an admitted limit - we can`t just say:
"oh, great! this cap can take 13 a rms - so i can power it with any
voltage at any frequency, but the current shouldn`t exceed 13 a" -
it`s not true.
>>capacitor temperature is determined by the power of heating loses in it
>>this power is determined from reactive power & dissipation factor - it`s
>>their multiplication - right?
>Yes for dielectric losses. But I2R losses are far higher than dielectric
>losses in our application and they are accounted for separately.
any practical numbers?
> Original poster: "Gerry Reynolds" <gerryreynolds@xxxxxxxxxxxxx>
> Trise = Power dissapation (watts) * Thermal Impedance (degrees/watt)
> Power dissapation = Irms^2 * ESR_of_cap
ESR = dissipation factor / (2 * PI * F *C)
so on 1 khz ESR will be significantly greater than on 500 khz (for
good RF cap), then Trise on 1 khz will be also significantly greater
than on 500 khz.
but Steve don`t believe in it:
>Original poster: Steve Conner <steve@xxxxxxxxxxxx>
>>it`s useless to write rms rating without its frequency!
>Not really. 10A RMS will heat a capacitor just the same whether it's
>at 1 kHz or 500 kHz.
so what the hell? :-)
---
Your not coiling unless your blowing capacitors! Then when you get
things worked out to where the capacitors stop blowing, you start
blowing transformers. (c) Richard Quick 11-03-93 20:42