Re: Magnetic Force with Tesla Coil?

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: Terry Fritz <teslalist-at-twfpowerelectronics-dot-com>

Hi,

Even though the current is hundreds if not thousands of amps in the 
primary, the duty cycle is very short (1%) so it sort of gets "hit" for 
about 100mS.  But in that tiny time, the metal just can't move very far due 
to it's mass even if the instant force is sort of high.

My OLTC uses thousands of amps and is solid state so it should run 
silent.  But you can "hear" the thing.  "Magnetoconstriction" of the 
primary circuit does make a little "crunch noise".  But not very significant.

I suppose one could figure out the force on the primary, take into account 
the copper's mass, and see how far it should move given the short time of 
the pulse.  Observations here suggest that the displacement is very "tiny".

Cheers,

         Terry

At 08:03 AM 7/9/2004, you wrote:
>Tesla list wrote:
>
>>Original poster: "Bob \(R.A.\) Jones" <a1accounting-at-bellsouth-dot-net>
>>Hi,
>>
>>Actually the magnetic field will only penetrate to a skin depth(1/e) of  the
>>material at the relevant frequency.   Which in the case of typical Tesla
>>coil frequencies is going to be 1mm or less for usually metals including
>>ferrous. In addition at typical Tesla coil frequencies phase of the induced
>>magnetic field will be such that on average its  repulsive. i.e. the induced
>>surface currents shield the bulk of the material. (Lenze's Law).
>>
>>  However I am not certain why the average force is less compared to the same
>>low frequency or dc field.
>
>     The force experienced depends on the material.
>     The characteristics of the materials vary with frequency.
>      Losses are higher at high frequencies: less force is experienced.
>
>>Presumably at low frequencies or DC the field can
>>be increased say a hundred times by ferromagnetic
>
>     The field is what it is (current times turns).
>      Ferromagnetic materiasl (If not lossy) will
>      concentrate the field in localized areas.
>      Air core (as Tesla, typically)  allows the fioeld to spread, and weaken.
>
>      best
>        dwp