[GreenKeys] History - Why voltages and frequencies are chosen (5v & 3.3v logic, 6.3v filaments, 120/220 VAC, 50/60Hz etc)

[Keith Mc]

I don't know if I ever asked this before.  I had a VERY interesting question 
arise (yet again) the other day, and STILL haven't yet found a good 
explanation for MANY of the "made choices" by the engineers yet.

Question - What is the history behind the CHOICES for voltages and 
frequencies - for logic, batteries, tubes (filaments & plates), 
mains V&F, etc?  
If arbitrary, then why do power supplies and load needs often NOT MATCH?

Does anyone have a link to any good "history of power supply voltage 
and frequency choices" stories, that covers these subjects?
(I'm sure this could fill books, but I'm looking for the Cliff Notes versions... :-)

I have my own musings (I'm included some below, to start the ball rolling), 
but I'm looking for specific thoughts and definite documentation on the 
"History of F&V Choices" for those different subjects.

Some examples of this kind of question:
- Tubes -  Why "6.3v" filaments? Why are plate supplies in increments of "22.5v"?
- Semi logic - why "5v" and 3.3V"?  
- Mains - Why "50Hz" and "60Hz"?  Why a particular line voltage?  Why did 
some countries or companies choose what they did for mains voltages and 
frequencies, instead of choosing the same as others nearby, for compatibility?
...etc...

I'm SURE many of these stories involve either basic Physics & Chemistry, 
or some practical mechanical reason.  But some choices may have also 
involved: politics, inter-company competition, "fostering a domestic 
producer", or simple patent avoidance. (Ex: we have so many different
screwdriver tip shapes, simply to avoid patents.)

I'm curious to hear what you all know, about such V&F choices...
Maybe ab Elmer "Tube Guy" can speak on tubes, or a "Semi Guy" on the
history of semiconductors, etc.   See below for some musings.

- Keith Mc.

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Some musings on the choices of voltages and frequencies.

BATTERIES - Battery voltages are fairly easy - Cell voltages are determined 
by "electrochemistry" (the "electronegativity") in physics, and how many cells
you decide to stack in a battery.  The electronegativity is the natural voltage 
difference produced when you use two dissimilar metals in a cell.  
Chose a different combination of materials and cell count, and you get 
the various results.

Trivia - There are very few "B batteries" now, because that's the letter 
used for "high voltage" tube plate batteries, in tube driven portable 
equipment.  You don't need them with semiconductors. Without 
demand, they're rarely made nor store stocked anymore.

AIRCRAFT LINE FREQUENCY - Another easy one - "400Hz" was chosen 
for aircraft AC power over "50Hz" or "60Hz",  simply because higher 
frequencies reduces the size and weight of the transformers needed 
on the plane to convert it around.  Weight is important in planes.

Mains Line Freq - LOW frequencies are necessary to reduce the 
"antenna effect",where the power simply disappears off of power lines
by radiating away.  But, the lower the frequency, the larger the 
transformer needed, which increases cost.  Therefore, I'm sure that
50/60Hz must be some kind of a "tradeoff" or "compromise" between the two.

But I don't know WHY those EXACT numbers were chosen, nor why
different countries chose differently. (Eg - Why not "40Hz"? "55.5Hz"?  etc.)
Does it perhaps have to do with the mechanical properties of the generators?
(eg - a "reasonable" axle speed, winding tech they could manage then, etc.?)

Mains Voltages -  I have NO clue as to why the mains voltage choices 
were made as they were, for any particular country. I'm SURE politics,
company competitions, and/or patents were SOMEHOW involved 
(Foster a "domestic producer" of equipment, avoid a patent lawsuit
or royalties, etc.)

I have also not found a good answer for the choices for voltages with
filaments and plates in Tube Tech, nor the reasoning for the specific 
choices in power supplies for Semiconductor Logic yet:

With the tubes I'm ASSUMING filament voltages probably had to 
do with the "easily produced voltages with the battery tech of the 
day", or maybe some simple integer math ratio for transformer 
windings when compared to mains voltages. But I can't pin the "6,3V"
choice down, nor why plate voltages are in "22.5v" increments. 
Anyone know?

Semi logic -  Similarly, WHY choose "5 volts" for digital logic, 
and now "3.3 volts"?

The 5V choice PROBABLY had to do with "total of the diode drops 
in a totem-pole output" using the semis of the day, but again I 
can't find a definitive answer source for that.  

Ditto with the SPECIFIC choice of "3.3 V".  I know they wanted 
to reduce the voltage, both to reduce power consumption,
AND require less batteries in products, but I'm trying to find why 
THAT exact number.  Again I'm assuming it probably has to 
do with the natural physics of diode drops in semiconductors, 
or batteries, but I don't have a good answer reference yet.


Bottom line - Does anyone have any links to good "history of voltage 
and frequency choices" stories, that covers ANY of these kinds 
of subject?  The specific number choices for voltage and frequencies 
have always intrigued me (and obviously others, for the question arose AGAIN).

Thanks again!
- Keith Mc.