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Re: coil losses

Hi Terry,

> Original Poster: Terry Fritz <twftesla-at-uswest-dot-net>
> 
> At 09:06 AM 6/14/99 +1200, "Malcolm Watts" <malcolm.watts-at-wnp.ac.nz> wrote:
> >Hi Terry,
> >          Great post:
> >          
> >> Original Poster: Terry Fritz <twftesla-at-uswest-dot-net>
> >> 
> >> Hi All,
> >> 
> >>     Here is a list of the losses in a Tesla coil I had laying around.  I
> >> forget the details but the numbers should be fairly typical.  I think this
> >> is an LTR design...
> >> 
> >> Primary Neon Windings = 29 watts
> >> Secondary Neon Windings = 21 watts
> >> Filter Resistors = 92 watts
> >> Primary Circuit Loss = 490 watts
> >> Secondary Circuit Loss = 17 watts
> >> Power to Arc = 127 watts
> >> Total = 776 watts
> >> 
> >> Note that almost half the coil's energy is being burned up in the gap.
> >> Capacitor losses and primary coil losses are comparatively low so the gap
> >> is eating power like mad...
> >> 
> >>     Terry
> >
> >I realized this early on by considering the noise, light and heat in 
> >the gap. BTW, a gap that is loud compared to the secondary discharge
> >means something can be done to considerably improve output at the 
> >same power level.
> >
> >Regards,
> >Malcolm
> >
> 
> Hi Malcolm,
> 
>     The terrible gap losses can be significantly reduced by good quenching
> trapping the primary energy in the secondary system so that it cannot be
> chewed up in the wasteful gap.  Of course, good quenching is much more
> easily said than done.  

Every attempt I've made at forcing a good quench suggests to me that 
it is achieved with higher wasteful primary losses. Better to achieve 
it with a strong ouput.

>     I would like to try a series gap like the ones I made from copper pipe
> sections in series with a rotary next.  Rotaries tend to be poor quenchers
> despite their other favorable characteristics.  Even timing critical LTR
> systems can support additional series gaps since the rotary still controls
> the timing.
> 
>     Backing off the coupling seems to help quenching too without a great
> effect on energy throughput.  With lower coupling, it just takes a bit
> longer to transfer the energy to the secondary.  However, if lower coupling
> allowed better quenching, the small energy loss caused by lower coupling
> would be far outweighed by the advantages of good quenching.
> 
> Cheers,
> 
>     Terry

Just re-reading that original post makes me think you are running the 
coil with air streamers. Yes? Transfer efficiencies can easily beat 
the 80% mark so the implication is that there are multiple energy 
trades going on in this coil which implies minimal output loading. 
That result is to be expected for air streamers but is very poor for 
attached discharges. 

    Agree with the comment about backing off the coupling. It does 
give the gap a quiet time for longer between trades and the loss is 
really quite minimal. It might also give the secondary a better 
chance to lose energy on earlier trades as it prolongs secondary ring 
time per trade.

Cheers,
Malcolm