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Re: Skin Effect
From: John H. Couture[SMTP:couturejh-at-worldnet.att-dot-net]
Sent: Tuesday, August 05, 1997 2:48 AM
To: Tesla List
Subject: Re: Skin Effect
At 04:00 AM 8/4/97 +0000, you wrote:
>
>From: Malcolm Watts[SMTP:MALCOLM-at-directorate.wnp.ac.nz]
>Sent: Sunday, August 03, 1997 4:28 PM
>To: tesla-at-pupman-dot-com
>Subject: Re: Skin Effect
>
>Hi Robert,
> If I might comment also....
>
>> From: Robert Davis[SMTP:RE.Davis-at-btinternet-dot-com]
>> Sent: Sunday, August 03, 1997 9:27 AM
>> To: 'Tesla List'
>> Subject: RE: Skin Effect
>>
>>
>>
>> Dear DR.RESONANCE,
>>
>> Sorry the calculation was not clear. I used the X as multiplication.
>> In the second calculation for effective wire resistance the skin depth
>> term varies with frequency. Also the lower case r was a typing
>> mistake. The ^ symbol meaning, to the power of. The 66 in the first
>> formula becomes 0.066 after converting skin depth in mm to meters.
>> The full equation is given below (without multiplication symbols)
>> after substituting the first formula for the skin depth term:
>>
>> Dynamic Resistance = L/C((PiR^2)-(Pi(R-(0.066/sqrt(F)))^2))
>>
>> Where:
>> F = Frequency (Hz)
>> L = Length of wire (m)
>> R = Radius of Conductor (m)
>> C = Conductivity of copper = 5.8 x 10^7
>> Pi = 3.1415927
>>
>> In the above I use sqrt() as the square root function.
>
>Firstly, 66/sqrt(f) gives the skin depth in mm at frequency f for
>copper or at least one grade of it. Resistivity/conductivity is
>already factored into this equation. Seems superfluous to use it
>twice?
>
>Malcolm
>
>---------------------------------------------------------------------------
Robert -
You can also use D = 2.6/sqrt(F)
Where D = Depth in mils
F = Frequency in megahertz
Example for copper at 500 KHZ
D = 2.6/sqrt(.5) = 3.7 mils
From the Tesla Coil Construction Guide
John Couture
>
>