Re: [TCML] 50Hz = 'short end of the stick?'

[3ldon Johansen <johansense@xxxxxxxxx>]

Back in the day, it made sense to use 50Hz, or 33Hz, or even 25Hz, and
there were even 16-2/3Hz systems in place
one reason for the lower frequency is more efficient transformers.
keep in mind that 600mT was on the high end for flux density in 1900,
and iron losses were very high before they discovered around 1910 that
adding silicon made everything so much happier.
Today its 1.2T minimum, and the new designs pushing 1.9T with an
amorphous strip wound core, so its less of an issue. (iron loss around
1 watt per kilogram at 1.8T 60Hz)
you beat us when it comes to the 16% savings on line compensation,
which might be a bigger savings than the 6% larger transformers.
though for anything under 100KW, higher frequency = higher efficiency
and lower cost *generally*
i do have access to 400hz at work, and will be building a TC this
year... (that will go over well)

why is the tank cap larger?





On Fri, Mar 26, 2010 at 8:01 PM, Christopher Karr
<chriskarr4@xxxxxxxxxxx> wrote:
>
> Hello everyone,
>
> I was curious as to the thoughts of list members about the line frequency versus the efficiency of their coils and their coils' components, as well as monetary-effectiveness
>
> For example, a line frequency which is lower results in a less-efficient
> transformer (weight:wattage) and a larger tank capacitor for the same voltage when compared to a higher frequency. Since they require a larger tank capacitor, the bang-energy is larger, but the repetition-rate (and, thus, streamer growth) is smaller (infrequent in comparison to a 400Hz system).
>
> So far, we have established that:
> 1) In 50Hz-Land(s), your transformer is more expensive and more heavy (due to materials) than in 60Hz-Land(s);
> 2) In 50Hz-Land(s) the tank capacitor must be of a larger value at the same voltage and, thus, more expensive;
> 3) The streamer-growth should be expected to be lesser in 50Hz-Land, due to a relatively low bang-frequency, and;
> 4) The bang-energy in a 50Hz system will be larger, which contributes to secondary coil arc-overs to primary, due to over-coupling (since there is a higher peak-current).
>
> For the remainder of this post/message, the focus will be on point (4).
>
> Since the bang-energy is larger, over-coupling is likely to occur, but if it does not (due to a primary resistance being sufficient to allow the capacitors to discharge in an appropriate time for the coil to quench before the next AC half-cycle begins, but not immediately), it is almost certain that the coil will further lose efficiency due to a lessened power-transfer (since the current is lower, the magnetic field is less affective upon the secondary coil).
>
> The point which seems obvious here is this - the higher the frequency of your coil (when not using a SMPS), the more efficient it should be in terms of weight, size and production cost, as well as output:$(input).
>
> As far as is clear, has anybody made this analysis before, or used the same coil on a 50Hz&60Hz line with transformers of the rated frequency and the same voltage & current output, as well as correcting primary capacitance to the same percentage above resonance?
>
> Thank you for your time (and patience, if this post is riddled with misconceptions - I am only sixteen years old, after all!),
>
>  - Christopher Karr
>
>
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