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Building Transformer & flux density
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From: Malcolm Watts [SMTP:MALCOLM-at-directorate.wnp.ac.nz]
Sent: Sunday, June 14, 1998 7:40 PM
To: Tesla List
Subject: Re: Building Transformer & flux density
Hi Erik,
> Sent: Friday, June 12, 1998 12:36 PM
> To: tesla-at-pupman-dot-com
> Subject: Building Transformer & flux density
>
> Hi,
> I am building a transformer for my tesla coil. =20
> I need to figure out the cross sectional area of the iron core. =20
> This would be related to max flux density in iron.
>
> F stands for flux, A is area,=20
> f is frequency, N number of turns,
> B is magnetic field, V is voltage
>
> F =3D B * A
>
> now for a close packed coil using faradays law
> Emf =3D -d/dt * N * F
>
> so if we substitute in for the flux F
> Emf =3D -d/dt * N * B * A
>
> Which can be rewritten as
> V =3D f * N * B * A
>
> Which can be rewritten as
> B =3D V / (f * N * A)
>
> ok I measured a NST and a H&R transformer and found
> for NST B =3D 7.34 Tesla
> for H&R B =3D 5.86 Tesla
>
> 5.86 and 7.34 Tesla seem kind of high to me. Am I missing=20
> a factor or two? Does this sound right? Is all the physics good?
I seem to remember that for sinusoidal AC there is a factor of 4.44
built into the denominator.
Malcolm