The origins of 60-Hz as a power frequency (1997)
265 comments
·February 7, 2025mrb
geor9e
Maybe this was obvious, but I will spell it out for slow people like myself:
60 Hz = 60 cycles per second = 3600 cycles per minute
A simple 2 pole AC motor spins 1 rotation per cycle, so 3600 RPM. AC is a sine wave cycle of current. Current flows one way to attract it to one pole, the current flows the other way to attract it to the other pole.
For a big mainframe disc drive, it sounds like the obvious choice. Why they stuck with it after switching to DC, who knows. Maybe they didn't want to redesign the controller circuits.
emmelaich
There was a brief stop off at 5400 at long the way.
Actually, still available. Good to have something quieter when performance requirements are not as high.
kees99
5400 is (was?) very common RPM for laptop HDDs.
Tempest1981
And apparently why we have LED car taillights that flicker annoyingly.
If anyone here works at a car manufacturer, please try to get this fixed. Apparently not everyone notices.
sathackr
It's PWM dimming. I see it most on Cadillac SUVs. Drives me nuts too.
They could design it not to be that low of a frequency but apparently someone thought that 40-50hz was imperceptible to humans and went with it
lutorm
I find it most annoying when moving your eyes. Anyone will notice the flicker if their eyes aren't stationary since then each "flick" will end up on a different part of the retina. So, instead of a normal motion blur you see a dashed line which is hard to ignore.
hunter2_
What's the cause? Alternators run at very high frequencies with good rectifiers, so I'm guessing the flicker is introduced by PWM dimming, but why would that be a low enough frequency to bother people?
I'm sensitive to flicker myself, but only on the more extreme half of the spectrum. For example, half rectified LED drivers on 60 Hz AC drive me nuts, but full rectified (120 Hz) I very rarely notice. I don't notice any problem with car tail lights, except in the case of a video camera where the flicker and the frame rate are beating. The beating tends to be on the order of 10 Hz (just shooting from the hip here) so if frame rates are 30/60/120 then I guess the PWM frequency is something like 110 or 130 Hz?
SV_BubbleTime
Automotive engineer here! I don’t do lights, so I have no idea!
BUT… I kinda do. You want the lowest PWM frequency you can get away with. In this case, at the back of the car, furthest from the battery, you really don’t want a 8kHz PWM nor do you need it. It costs money to isolate the supply demand, so you don’t want a noisy field for no reason. The “good enough” frame rate is 60Hz static, not moving, no other flashing lights, not using a camera, etc.
60Hz or 60fps has issues though. If you expose a PWM LED to another flashing light or movement you get really bad imaging. Imagine you took an LED in your hand and shook it, at 60 Hz you will see snapshots of where the LED was as you’re shaking it. At 240Hz you will see a blur. Guess which is better for a vehicle?
I figure most car LED taillights internal to their housing would be 200-1000Hz depending on factors but I haven’t ever measured.
200Hz PWM is a really common value. No need for Samaritan base-12 here.
For halogen and incandescent, we use PWM, fun fact. Low Hz though! About 88Hz, depending on voltage. You might wonder why. We can get 98% of the light output with 85% of the required wire. It’s all about weight and cost. Although not many vehicles use this anymore.
brandmeyer
> introduced by PWM dimming, but why would that be a low enough frequency to bother people?
The human fovea has a much lower effective refresh rate than your peripheral vision. So you might notice the flickering of tail lights (and daytime running lights) seen out of the corner of your eye even though you can't notice when looking directly at them.
arcanemachiner
I see it, but only in my peripheral vision. Drives me nuts.
taneq
This is because your cones (colour-specific 'pixels' in your retina) cluster around your fovea (high-resolution area around the center of focus) while the rods (black-and-white, bigger, dumber, but much more sensitive and therefore faster-responding 'pixels') fill the rest of your visual field. Rods respond fast enough to see the flicker but cones don't.
You might also notice in light that's almost too dim to see, you can see things better if you look a bit to the side of them, for the same reason.
Tempest1981
For me, it's also noticeable when my eyes are sweeping from one object to another. Like you should be doing when driving. I guess that's somewhat peripheral, but not entirely.
Find a Cadillac Escalade with the vertical LED lights, and give it a try.
What's a good way to capture this on video? Or to measure the frequency?
spockz
Or for some reason in the rear view and side mirrors!
hcarvalhoalves
Also 5400rpm HDDs were common – that would be 1,5x factor.
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Ericson2314
https://en.wikipedia.org/wiki/Amtrak%27s_25_Hz_traction_powe... predates standardized 60 Hz, and still hasn't been converted (!!)
_trampeltier
Switzerland trains still use 16,7 Hz (16 2/3Hz)
Ericson2314
Yes indeed, but the German-Swiss-Austrian 16.7 Hz system is many orders of magnitude bigger than the Southend Electrification! The path dependency is much more understandable in that case.
cenamus
It's also 16.7 Hz precisely (save for the fluctuations) and not 16 2/3 Hz, for some electrical reasons regarding transorming 50 Hz to 16.7 Hz mechanically, which I don't completely understand
486sx33
Ontario, Canada, at niagara falls generated 25hz for industry (stelco and others) until the early 2000s https://www.lifebynumbers.ca/history/the-rise-and-fall-of-25...
sathackr
Large parts of the NE corridor train line(DC to NY and New Haven to Boston) still operates at 25hz and has its own power system and generators because of it.
layer8
To cite the main origin:
> Stillwell recalled distinctly the final meeting of the committee at which this recommendation was agreed upon. They were disposed to adopt 50 cycles, but American arc light carbons then available commercially did not give good results at that frequency and this was an important feature which led them to go higher. In response to a question from Stillwell as to the best frequencies for motors, Scott said, in effect, “Anything between 6,000 alternations (50 Hz) and 8,000 alternations per minute (67 Hz).” Stillwell then suggested 60 cycles per second, and this was agreed to.
rkagerer
Link straight to PDF: https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=628...
Kelvin506
This seems to yield only the summary, not the full paper?
rkagerer
Seems the link stopped working. When I posted, it linked straight to the PDF (I even tested in an incognito window at the time).
Fil0sOFF
This one seems to work https://ieeexplore.ieee.org/stampPDF/getPDF.jsp?arnumber=628...
gorfian_robot
I think the full paper requires an IEEE account. :(
freeqaz
If we could magically pick a frequency and voltage for electrical systems to use (without sunk costs), what would it be?
What's the most efficient for modern grids and electronics?
Would it be a higher frequency (1000hz)?
I know higher voltage systems are more dangerous but make it easier to transmit more power (toaster ovens in the EU are better because of 240v). I'm curious if we would pick a different voltage too and just have better/safer outlets.
burnerthrow008
> If we could magically pick a frequency and voltage for electrical systems to use (without sunk costs), what would it be?
> What's the most efficient for modern grids and electronics?
I do not think it is possible to answer the question as posed. It is a trade-off. Higher frequencies permit smaller transformers in distribution equipment and smaller filtering capacitors at point of use. On the other hand, the skin effect increases transmission losses at higher frequencies.
If you want minimum losses in the transmission network, especially a very long distance transmission network, then low frequencies are better.
If you want to minimize the size and cost of transformers, higher frequencies might be better. Maybe the generator is close to the user so transmission loss is less important.
If you want smaller end-user devices, high frequency or DC might be more desirable.
You have to define some kind of objective function before the question becomes answerable.
willis936
I think the question could be constrained as "what frequency uses the minimum amount of copper to remake the electrical distribution network that exists today?"
This would be a pretty good approximation of the ratio of transmission lines to transformers.
Panzer04
You could build the lot with DC and massively reduce transformers, but transformers are probably a lot more reliable than switching converters everywhere. Not sure which would be cheaper tbh.
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TheSpiceIsLife
Distribution lines are aluminium.
NooneAtAll3
this gives a wrong assumption that optimal distribution network is _the same_ for different frequencies
or that it, itself, isn't a consequence of its own series of sunken cost fallacies
im3w1l
Wouldn't it make sense to do both then? Low frequency or even dc long distance transmission that gets converted to standard frequency closer to the user?
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connicpu
There's considerable losses involved when you want to convert between frequencies. DC also has considerable losses over long distance, so there's a lower bound on the frequency before the efficiency starts to go down again.
osigurdson
Objective function: Minimize operational cost Decision variable(s): Electrical system frequency Scope: Global electrical grid
Brian_K_White
2 meaningless statements.
For instance, I would say that the scope of the global electrical grid includes every phone charger. Not just because the last foot devices are techically connected, but because they are the reason the rest even exists in the first place. So nothing that serves either the long haul or the local at the expense of the other can be called "minimal operational cost".
So trains use their own 25hz or even lower because that's good for long haul. But that would mean phone chargers are undesirably large and heavy. Or maybe it would mean that every house has it's own mini power station that converts the 25hz utility to something actually usable locally.
Meanwhile planes use 400hz 200v 3-phase for some mix of reasons I don't know but it will be a balance of factors that really only applies on planes. Things like not only the power to weight but also the fact that there is no such thing as mile long run on a plane, the greater importance to avoid wires getting hot from high current, etc.
Simply saying "the objective function is 'what is best?' and the scope is 'global'" doesn't turn an undefined scope and objective into defined ones.
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redox99
You could push it to 100hz, MAYBE 200hz at most. Higher than that, transmission losses due to skin effect would make it a bad idea. Also generator motors would require too high RPM.
240v is a good middle ground for safety and power.
anticensor
For 1kHz, you'd run the generators at the same speeds you run them for 50Hz but with 20 times as many poles.
Workaccount2
Higher Voltage: Less conductor material needed, smaller wires. But need more spacing inside electronics to prevent arcing, and it becomes more zappy to humans. Also becomes harder to work with over 1kV as silicon kind of hits a limit around there.
Higher Frequency: Things that use electricity can be made smaller. But losses in long transmission become much worse.
DC instead of AC: Lower losses in transmission, don't need as much spacing inside electronics for arcing. But harder and less efficient to convert to different voltages.
UltraSane
The skin effect causes AC current density J in a conductor decreases exponentially from its value at the surface J_S according to the depth d from the surface. The depth decreases as the square root of frequency. This means that the effective power a wire can carry decreases with increasing AC frequency.
Zardoz84
at same time, high frequency makes high voltage secure (or more secure) I receive 15KV discharges at high frequency and I live to write about it.
andrewla
Impulse Labs has built an induction range that has super high power; their trick is that they have a battery that they recharge from the mains. Might be expensive but the same technique could work for a toaster (or for a water kettle) to basically keep a whole bunch of energy in reserve and deliver it when needed.
marssaxman
That's a great idea - I wonder if electric kettles would be more popular in the US if they worked as quickly as they do on 240V? How large a volume of battery would one need to accomplish this, I wonder?
nicoburns
Unfortunately quite a large one. Electric kettles are typically one of the highest power draw items in a typical household. A 3kw kettle would need a ~250wh battery for a 5 minute boil (+ electronics capable of sustaining 3kw for that time period and recharging the battery at a reasonable rate afterwards). This would likely be larger than the entirety of the rest of the kettle with current technology.
duskwuff
I'm not sure it'd be commercially viable. A stove is a major home appliance, and the Impulse Labs unit is a high-end one with a price tag of $6000. An electric kettle, on the other hand, is considered a near-disposable piece of home electronics with a price closer to $50; it'd be hard to build a substantial battery into one at an affordable price.
bobthepanda
Electric kettles mostly aren’t popular because of a perceived lack of need.
Most Americans don’t drink tea and most coffeemakers heat water themselves. For most other applications using a pot on a stove is not a deal breaker.
Borealid
I wouldn't want a kettle that wears out after only 3-10 years of use.
avidiax
> electric kettles would be more popular in the US if they worked as quickly as they do on 240V
Euro standards are 8-10A 240V circuits. I have an EU kettle, and it draws max 2200W.
US standards are 15A 120V circuits. It could draw 1800W, though some kettles might limit to 12A and draw 1440W.
So a Euro kettle might have 22%-52% more power than a US, which increases a 4 minute boil to 4m53s or 6m7s worst case.
So it seems like it's not a significant factor, though it would be useful if US kettles really maximize power.
jamesy0ung
As an Aussie, it’s weird to think that induction and other cooking appliances are so slow or expansive. We have a $200 AUD induction stovetop from Aldi that draws up to 7.2kw across 4 pans
buildsjets
Aircraft AC electrical systems are 115V 400Hz, allegedly to minimize component weight.
throw0101c
> Induction motors turn at a speed proportional to frequency, so a high frequency power supply allows more power to be obtained for the same motor volume and mass. Transformers and motors for 400 Hz are much smaller and lighter than at 50 or 60 Hz, which is an advantage in aircraft (and ships). Transformers can be made smaller because the magnetic core can be much smaller for the same power level. Thus, a United States military standard MIL-STD-704 exists for aircraft use of 400 Hz power.
> So why not use 400 Hz everywhere? Such high frequencies cannot be economically transmitted long distances, since the increased frequency greatly increases series impedance due to the inductance of transmission lines, making power transmission difficult. Consequently, 400 Hz power systems are usually confined to a building or vehicle.
* https://aviation.stackexchange.com/questions/36381/why-do-ai...
kristianp
Do electric car motors make use of this property too? I know some cars, such as Porches use higher voltage to enable faster charging.
6SixTy
Very much true. A higher switching frequency means that a smaller transformer is needed for a given power load.
In reference to consumer power supplies, only reason why GaN power bricks are any smaller than normal is because GaN can be run at a much higher frequency, needing smaller inductor/transformer and thus shrinking the overall volume.
Transformers and inductors are often the largest (and heaviest!) part of any circuit as they cannot be shrunk without significantly changing their behavior.
Ref: Page 655, The Art of Electronics 3rd edition and Page 253, The Art of Electronics the X chapters by Paul Horowitz and Winfield Hill.
DrBenCarson
The higher the voltage the less power lost to resistance and the less money spent on copper
Short protection at the breaker for every circuit would probably be necessary at that voltage
xanderlewis
Why are toasters better at 240V? Can’t you just pull more current if you’re only at 120V (or whatever it is in the US) and get the same power?
I guess there’s some internal resistance or something, but…
nwallin
Correct. You can get the same power with half the voltage by doubling the current.
The trouble is the wires. A given wire gauge is limited in its ability to conduct current, not power. So if you double to the current, you'll need to have roughly twice as much copper in your walls, in your fuse panel, in your appliance, etc.
Additionally, losses due to heat are proportional to the current. If you double the current and halve the voltage, you'll lose twice as much power by heading the wires. For just a house, this isn't a lot, but it's not zero.
This is why US households still have 240V available. If you have a large appliance that requires a lot of power, like an oven, water heater, dryer, L2 EV charger, etc, you really want to use more voltage and less current. Otherwise the wires start getting ridiculous.
This is not to say that higher voltage is just necessarily better. Most of the EU and the UK in particular has plugs/outlets which are substantially more robust and difficult to accidentally connect the line voltage to a human. Lots of people talk about how much safer, for instance, UK plugs/outlets are than US plugs. If you look at the numbers though, the UK has more total deaths per year to electrocution than the US, despite the fact the US is substantially more populous. This isn't because of the plugs or the outlets, US plugs really are bad and UK plugs really are good. But overall, the US has less deaths because we have lower voltage; it's not as easy to kill someone with 120V as 240V.
So there's a tradeoff. There is no best one size fits all solution.
Liftyee
This is a very well written comment overall, but the energy loss in the wire is even worse than stated!
By modelling the wire as an (ideal) resistor and applying Ohm's law, you can get P = I^2*R. the power lost in the wire is actually proportional to the square of current through it!
Therefore, if you double the current, the heat quadruples instead of doubling! You actually have to use four times the copper (to decrease resistance by 4x and get heat under control), or the wasted energy quadruples too.
Crucially, voltage is not in the equation, so high voltages - tens or hundreds of kilovolts - are used for long distance power transmission to maximise efficiency (and other impedance-related reasons).
shaky-carrousel
In 2017, there were 13 electrocution-related deaths in the UK. In the US, there are between 500 and 1,000 electrocution deaths per year. This translates to 0.019 deaths per 100,000 inhabitants in the UK and between 0.149 and 0.298 deaths per 100,000 inhabitants in the US.
masfuerte
Your deaths claim surprised me. AFAICT England has ~10 deaths by electrocution per year. The US has ~100 domestic electrocutions and even more occupational electrocutions.
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andruby
I don’t know is toaster are close to max power draw, but kettles certainly are.
Most places with 240V regularly have 16A sockets, allowing a maximum draw of 3840W of power. That’s the limit. Cheap fast kettles will often draw 3000W and boil 250ml of water at room tempature in 30s.
Kettles in the US are often limited to 15A and thus max 1800W (usually 1500W) and take twice as long (60s)
Technology Connections has a great video on this: https://youtu.be/_yMMTVVJI4c
andrewla
I mention Impulse Labs and their battery-assisted 120V high power induction range in the comments elsewhere. Seems like a similar concept could be used to make an incredibly powerful kettle; throw in a battery that charges from the mains, and when you ask to boil, send in 20kW and boil the 250ml in 4 seconds.
4.18 J/g/C * 250g * (1/ 20,000 kJ/s) * 75C = 3.918swongarsu
Houses are wired for 16A per circuit on both sides of the pond, with high-power appliances typically pulling around 10A to avoid tripping the fuse when something else is turned on at the same time. It's just a nice point where wires are easy to handle, plugs are compact, and everything is relatively cheap.
The US could have toasters and hair dryers that work as well as European ones if everything was wired for 32A, but you only do that for porch heaters or electric vehicle chargers.
mystified5016
No, the standard in the US is 15 or 20A. 20 is more popular nowadays.
240V appliances typically get a 35 or 50A circuit.
But then you also have to deal with the fact that a lot of homes have wiring that can only handle 10A, but someone has replaced the glass fuse with a 20A breaker. Fun stuff.
bbatha
More current needs thicker wires. The average US outlet is wired for 120v15amp. 20 amp circuits are somewhat common, though 20amp receptacles are not. Certainly not enough for commodity appliances to rely on.
Going to more than 20amp requires a multiphase circuit which are much more expensive and the plugs are unwieldy and not designed to be plugged and unplugged frequently.
quickthrowman
> Going to more than 20amp requires a multiphase circuit
There is no multi-phase power available in the vast majority of US houses. A typical residence has a 120/240 split-phase service, which is single-phase only. A service drop is two hot conductors from two of the three transformer phases and a center-tapped (between the two hot legs) neutral conductor. Either hot leg is 120v to ground and line to line is 240V.
> https://en.m.wikipedia.org/wiki/Split-phase_electric_power
Single-phase breakers are also available in sizes larger than 20A, usually all the way up to 125A.
generallee5686
Having more current running through a wire means thicker wires. Higher voltage means less current to achieve the same power, so thinner wires for the same power. The tradeoff for higher voltage is it's more dangerous (higher chance of arcing etc).
ajuc
You need thicker wires for the same power. Which is why Americans live in constant fear of power extension cords, and people in EU just daisy-chain them with abandon.
extraduder_ire
If you're in a country that uses type-G plugs, almost* all of those extension cords have fuses that break well below the current that will cause a problem.
* Currently using a cable spool which will have problems before blowing the fuse if it's wound up and I draw too much current. It has a thermal cutoff, but I still unspool some extra wire on the floor.
tgsovlerkhgsel
You need the same thickness of wire for 10A regardless of which voltage you have. So with 230V, your 10A wire will let you draw 2.3 kW while someone with 120V and 15A wire would only get 1.8 kW and pay more for the wiring.
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UltraSane
Fun fact: Japan uses BOTH 60Hz and 50Hz for mains electricity due to historical generator purchases. This means the Japanese electric grid is split into two regions that cannot easily share electricity.
_trampeltier
The US alone has 3 grids (East, West and Texas). With the same frequency but still not connected.
In Switzerland trains use 16.7Hz but they are connected with large frequency inverters. Before it was with large motors / generators. Now its just static with electronic.
trothamel
The same frequency, but not connected via AC. There are multiple DC and Variable Frequency Transformer ties between the various interconnections.
https://en.wikipedia.org/wiki/North_American_power_transmiss...
cf100clunk
Exactly, DC is used for those links that would otherwise be out of synchronization. In Canada one of the DC links goes from the North American grid on the British Columbia Lower Mainland in Delta via a single underwater cable over to Vancouver Island. The water is the other conductor, and also keeps the cable cool.
fyrn_
This is covered in some detail in this paper? They even discuss the two engineers who made the purchase and who manufactured the generators..
themaninthedark
I want to say this was part of the issue after the Tohoku Earthquake, my recollection was that some generators got brought in to support the ones that were flooded but were incompatible. However, I can not find any note of it in the timelines and after-action reports that showed up when I searched.
So possibly misremembering or fog of war reporting, or perhaps not important enough for the summaries.
krackers
I like the hypothesis by fomine3 on HN that "Japan's divided frequency situation made Japanese electric manufacturers to invent inverter for electrics (example: air conditioners, microwave, refrigerators). Inverter primary makes electrics controllable efficiently, also they can ship same product (same performance) for both 50/60Hz area in Japan."
userbinator
It also has the most "Metric" of mains voltages, 100V nominal instead of the 110/115/120 or 220/230/240 that's common everywhere else in the world.
antithesis-nl
(1997), which I wondered about due to the "Many people continue to be affected by the decisions on frequency standards made so very long ago" phrasing and the intro-bit about the need for adapters in the paper itself.
Because these days, voltage and especially frequency are pretty much irrelevant for mains-power AC, and "ignorant" will be more accurate than "affected" when it comes to "many people"...
bluGill
They don't know it but they likely have a motor someplace in their house that runs at the speed it does because of frequency. They are ignorant but it affects them.
theamk
It is less and less likely... motor-based clocks are a thing of the past; hand appliances (like mixers and blenders) use either DC or universal motors to allow speed control. Even refrigerators feature "variable speed motors" nowadays, which means they are frequency-independent.
I think fans will likely be the last devices which care about frequency.. but new ones are often 12V/24V-based, with a little step-down modules.
quickthrowman
Most commercial AC fan and pump motors are already powered by variable frequency drives, and a lot of newer residential appliances have EC motors to allow for speed control.
I’m seeing more and more EC motors in commercial applications, for things like 2-3 HP fam motors and pumps.
satiric
What about dryer motors? I mean, I don't much care what rpm the dryer runs at, but it should change speed with the grid frequency right?
creeble
True for consumers (houses), not true for industrial applications where motors are in the >100HP range.
bluGill
Fans because a furnace only needs two speeds at most.
ethbr1
If only we could tag thought threads for submissions. Funny to see this coming out of the Baltic disconnect comment section!
alexjplant
Tangentially related: I have a vague memory of reading somewhere that the PCM sampling frequency for CD Audio was decided between Sony and Phillips by way of a surf contest. Their respective frequencies of choice were such that they could fit some arbitrarily-long piece of classical music onto a single disc so they decided to battle it out on the waves (the conference where they were hashing this out was in Hawaii). Phillips supposedly won so we got 44.1 kHz.
I just did a cursory web search to find this anecdote and was unsuccessful. Did I make this up whole cloth or is it just buried someplace? Or was I bamboozled at a young age by some random forumite on a now-defunct site?
*EDIT: This comprehensive account [1] seems to confirm that the story is completely apocryphal.
[1] https://www.dutchaudioclassics.nl/The-six-meetings-Philips-S...
hunter2_
Sony won, not Philips. It seems that the rationale is like so: a higher rate would not be compatible with both NTSC and PAL VCRs, and a lower rate would shrink the transition band for the antialiasing filter (or alternatively, reduce usable audio bandwidth to an extent that encroaches on the generally accepted limit of human hearing). Although the latter hardly seems relevant when the alternatives being debated were so close (Philips' 44056 Hz, for example)!
alexjplant
> a lower rate would shrink the transition band for the antialiasing filter (or alternatively, reduce usable audio bandwidth to an extent that encroaches on the generally accepted limit of human hearing)
I've seen people smarter than me argue that the ideal sampling rate is actually somewhere around 64 kHz because it would allow for a gentler anti-aliasing filter with fewer phase artifacts.
anticensor
Why couldn't they make use of a sampling rate with five samples per frame (which would exactly give 88.2kHz by the way)?
wappieslurkz
Because doubling the sample rate would half the playing time of a CD, or require twice the density, while not bringing any audible increase in quality for the human ear.
null
Aloha
I know Southern California Edison had 50hz power, I always used to find old clocks and radios as a kid with a conversion sticker.
I've always kept an eye out for good papers about the effort to convert, but they're hard to find.
pkulak
I always assumed it's because 60 is a highly composite number (superior, in fact!). It's kinda the best number if you're ever going to need to divide. 50 is kinda garbage in that regard. :/
layer8
Well, 50 Hz means the period is a round 20 ms instead of 16.6666… ms.
And PAL got a higher resolution thanks to it.
pkulak
At the cost of framerate. No free lunch!
tzs
Another point in favor of 60 is there are 60 seconds in a minute and 60 minutes in an hour. If you make the frequency 60 cycles/second then you only need divide-by-60 circuits to derive 1 cycle/second, 1 cycle/minute, and 1 cycle/hour.
With 50 cycles/second you would need both divide-by-50 and divide-by-60.
beeflet
It's worth mentioning 60Hz vs 50Hz distinction has ended up having a knock-on effect on framerate standards because of early TVs using it for timing, not to mention market segmentation because different products had to be manufactured for the US vs European markets.
here is a well animated video about it: https://www.youtube.com/watch?v=DyqjTZHRdRs&t=49s
PortiaBerries
Yes! I was looking for this comment. Maybe because I didn't grow up with the metric system, but 60 feels like a much "rounder" number to me than 50.
makerdiety
The number sixty is highly composite maybe because it's a multiple of three? In which case, I can see why Nikola Tesla liked the number three or multiples of three.
So he can do exploratory electrical science and analysis with flexible cases?
throw0101c
Meta: the IEE(E) has been around for a little while. One of the references:
> [5] L.B. Stillwell, ”Note on Standard Frequency,” IEE Journal, vol. 28, 1899, pp. 364-66.
That's 126 years ago.
The 60 Hz grid is why we have HDDs spinning at 7200 RPM. Because of 60 Hz, it was simpler to design AC electrical motors to spin at 3600 RPM or 7200 RPM (1x or 2x factor). When DC motors were made, for compatibility with AC motors, they often spun at the same speed (3600 or 7200 RPM) even though there was no electrical reason to do so. When HDD manufacturers selected DC motors for their drives, they picked 3600 RPM models as they were very common. Then, for performance reasons, in the 1990s, 7200 became more common than 3600 eventually.