The origins of 60-Hz as a power frequency (1997)

https://ieeexplore.ieee.org/document/628099

by theamk • 1 year ago

171 251 1 year ago

ieeexplore.ieee.org

ethbr13• 1 year ago

If only we could tag thought threads for submissions. Funny to see this coming out of the Baltic disconnect comment section!

timcobb• 1 year ago

Thought threads?

ethbr13• 1 year ago

https://news.ycombinator.com/item?id=42973958

antithesis-nl• 1 year ago

(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"...

bluGill3• 1 year ago

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.

theamk2• 1 year ago

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.

rkagerer2• 1 year ago

Link straight to PDF: https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=628...

Kelvin506• 1 year ago

This seems to yield only the summary, not the full paper?

gorfian_robot2• 1 year ago

I think the full paper requires an IEEE account. :(

rkagerer2• 1 year ago

Seems the link stopped working. When I posted, it linked straight to the PDF (I even tested in an incognito window at the time).

ethbr13• 1 year ago

Tl;dr - Because Westinghouse (60 Hz) beat out GE (50 Hz) in the early (~1910+) American AC electrical equipment market.

SigmundA2• 1 year ago

My Tl;dr would be a little longer - early systems used both higher (around 130 hz) which caused issues with resonance and difficulties making induction motors, and lower (around 30hz) which caused light flicker.

50-60 hz solved these issues, Westinghouse thought 60hz was better for light flicker and beat out GE who settled on the 50hz standard used by it's European affiliate that moved up from 40hz due to flicker.

cf100clunk2• 1 year ago

25hz too, mentioned in another thread.

Analemma_• 1 year ago

In Seattle you can take a tour of the Georgetown Steam Plant, which was an early power station. At one point they mention that the plant had two totally separate generators at different frequencies: one for household mains power and one for the electric streetcars.

MBCook• 1 year ago

But that TLDR doesn’t answer why those companies chose those frequencies.

Ericson23142• 1 year ago

https://en.wikipedia.org/wiki/Amtrak%27s_25_Hz_traction_powe... predates standardized 60 Hz, and still hasn't been converted (!!)

_trampeltier2• 1 year ago

Switzerland trains still use 16,7 Hz (16 2/3Hz)

Ericson23142• 1 year ago

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.

486sx33• 1 year ago

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...

sathackr2• 1 year ago

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.

alex_young• 1 year ago

60 Hz sure makes it easy to keep clocks on time.

hatsunearu• 1 year ago

1/60th of a second isn't a common unit of time though

toast0• 1 year ago

It's convenient to count 60 pulses to make a seconds pulse, then 60 of those to make a minute pulse, then 60 of those to make an hour pulse. Then 60 of those to make 2 and a half days :P

theamk2• 1 year ago

As far as clocks are concerned, 60 Hz or 50 Hz are very similar, just make sure the number of teeth on gears match the frequency.

ThisNameIsTaken• 1 year ago

Not sure it's precise enough though. In 2018, many clocks in Europe were off because the frequency on the net had drifted due to (as I understood it) the network being out of sync across various countries. Some here might actually understand the details of this.

wongarsu2• 1 year ago

The frequency drifts up and down whenever demand doesn't exactly match supply. Higher demand slows the frequency down, higher supply speeds it up. This is actually the main way power companies know if supply and demand match, and if power stations have to ramp up or down.

The frequency changes are pretty small in normal operation, but on a clock that uses the frequency to keep time they accumulate. They only work reliably because power companies know about them and occasionally deliberately run a bit over or under capacity to make the average match again.

nottorp• 1 year ago

I don't think 60 or 50 Hz matters wrt to this.

The only thing that matters is that a clock that expects a certain frequency gets that frequency and not 1% more or 1% less.

mystified50162• 1 year ago

In the US, we modulate (or used to) grid frequency specifically for these analog clocks such that in a 24hr period it averages to exactly 60Hz.

It doesn't really matter on a second-to-second timescale how accurate grid frequency is. If you can keep the average frequency right, all your clocks will speed up and slow down in sync, and average out to 24hours per day

nom• 1 year ago

think again

Jedd• 1 year ago

The two clocks I reference the most - my wrist watch, and my mobile phone - don't really benefit from the alleged advantage of having mains power cycling every 0.0167 seconds.

Perhaps you could expound further on this hypothesis?

I'd always assumed people who spent 3+ years studying electrical engineering had solved this problem. Certainly in Australia (~240V / 50Hz) we don't seem to have a problem with all our clocks being 20% wrong all the time.

timw4mail• 1 year ago

I'm sure it makes the gear ratios easier to calculate for the power-frequency-synced gearing on those old electric clocks.

But now? It's pretty much just an implementation detail.

UltraSane2• 1 year ago

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.

_trampeltier2• 1 year ago

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• 1 year ago

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...

Aloha2• 1 year ago

We have more than three interconnections that are not in synchronous connection to each other.

They can share power and are somewhat connected with HVDC interconnections however.

fyrn_• 1 year ago

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• 1 year ago

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• 1 year ago

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• 1 year ago

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.

voxadam• 1 year ago

(1997)

1-6• 1 year ago

Duodecimal Society members are happy.

pkulak2• 1 year ago

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. :/

beeflet• 1 year ago

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

makerdiety• 1 year ago

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?

PortiaBerries• 1 year ago

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.

layer82• 1 year ago

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.

pkulak2• 1 year ago

At the cost of framerate. No free lunch!

tzs3• 1 year ago

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.

freeqaz2• 1 year ago

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.

IncreasePosts• 1 year ago

I don't care what the frequency is, I just want my LEDs to not flicker!

xanderlewis4• 1 year ago

What about if they flickered at 10^-15Hz?

sxp• 1 year ago

Normal LED lightbulbs shouldn't flicker on standard 60Hz circuits. Do you have a dimmer switch or smart switch in the circuit? I've noticed these cause flickering that's visible on camera or out of the side of my eyes.

SSLy• 1 year ago

that means that either the breaker is faulty, or the power stabilizator in the lamp itself is junk.

lnsru• 1 year ago

Get better ones. I installed expensive LED lamps at home and they’re fine. The guys in the office picked the cheapest ones and I don’t want to turn these ugly things on.

Edit: Paulmann Velora are the expensive lamps at home.

homebrewer• 1 year ago

https://lamptest.ru tests for flicker too. I don't know if those models are sold in the US, though. Philips, Osram and IKEA should be.

xanderlewis4• 1 year ago

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…

mypgovroom• 1 year ago

You have a 240v toaster?

bbatha• 1 year ago

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.

generallee5686• 1 year ago

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).

wongarsu2• 1 year ago

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.

tgsovlerkhgsel• 1 year ago

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.

andruby• 1 year ago

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

nwallin• 1 year ago

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.

ajuc• 1 year ago

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.

DrBenCarson• 1 year ago

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

UltraSane2• 1 year ago

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.

https://en.wikipedia.org/wiki/Skin_effect#Formula

Zardoz84• 1 year ago

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.

redox99• 1 year ago

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.

anticensor3• 1 year ago

For 1kHz, you'd run the generators at the same speeds you run them for 50Hz but with 20 times as many poles.

andrewla2• 1 year ago

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.

marssaxman3• 1 year ago

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?

jamesy0ung• 1 year ago

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• 1 year ago

Aircraft AC electrical systems are 115V 400Hz, allegedly to minimize component weight.

throw0101c2• 1 year ago

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...

6SixTy• 1 year ago

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.

freeqaz2• 1 year ago

Interesting to think about what the future could look like. What if breaker boxes were "smart" and able to negotiate higher voltages like USB-C does? It would avoid the problem of a kid sticking a fork in an outlet, or a stray wire getting brushed accidentally when installing a light fixture.

Time will tell!

duskwuff4• 1 year ago

What if breaker boxes were "smart" and able to negotiate higher voltages like USB-C does?

That'd be difficult; a breaker typically feeds an entire room, not a single outlet. (And when it does feed a single outlet, that's typically because it's dedicated to a specific large appliance, like an air conditioner or electric stove, which wouldn't benefit from being able to dynamically negotiate a voltage.)

pgalvin• 1 year ago

It would avoid the problem of a kid sticking a fork in an outlet

One of the best things about living in the UK! https://www.youtube.com/watch?v=UEfP1OKKz_Q

burnerthrow0082• 1 year ago

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.

im3w1l• 1 year ago

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?

willis9362• 1 year ago

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.

osigurdson4• 1 year ago

Objective function: Minimize operational cost Decision variable(s): Electrical system frequency Scope: Global electrical grid

Workaccount2• 1 year ago

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.

Max-q• 1 year ago

Today, with swichmode supplies, I think DC would make most sense. We lose much power to frequency deviation and inductive loads causing phase shift.

It would also make sense to have a high voltage and low voltage nets in houses. Low voltage for lighting and other low power equipment. High voltage for power hungry equipment. For example 48V and 480V.

Dylan168072• 1 year ago

Do we really lose much to phase shift? Increasing apparent load only causes a tiny fraction of that much waste, and local compensation isn't very expensive.

DC or a significant frequency boost would be good inside a house for lights and electronic items. Not so great for distribution.

I'm not convinced multiple voltages would be a net benefit outside of the dedicated runs we already do for big appliances.

frrlpp• 1 year ago

DC high voltage (200v) is very dangerous and pernicious, and mores difficult to switch on and off because of arcs.

xxs3• 1 year ago

Would it be a higher frequency (1000hz)?

Totally not, that would mean both worse skin effect and worse impedance. Likely the best option (if you really don't care about the existing infrastructure) would be DC, 0Hz. There are some downsides of DC, of course.

gosub1003• 1 year ago

This would be excellent for solar because it removes the efficiency loss from the inverters. AFAIK it's very hard to add/remove loads without spiking power to everything else on the line. A friend of mine applied for a job at a company that was trying to run DC in the home but it's not a trivial endeavor.

pwrson• 1 year ago

Probably about the same as we have.

Higher frequencies have terrible transmission (skin effect, transmission line length limit) and would start to interfere with radio.

Lower frequencies need larger transformers.

DC while nice is too expensive.

So about where we are now.

dreamcompiler• 1 year ago

DC. Modern electronics make AC grids unnecessary.

48VDC inside homes would be enough for most applications except heating and it would be kid-safe.

240V for heating applications.

1970-01-01• 1 year ago

Without sunk costs, objectively it's 000Hz. Voltage is mostly irrelevant too.

https://en.wikipedia.org/wiki/High-voltage_direct_current

cjohnst2• 1 year ago

When f is 60Hz, it makes for some nice round numbers, and easier for mental calculations.

ω=2πf

At 60Hz, ω is 376.99... very near to the integer 377.

Also, Z₀, impedance of free space is not far off at 376.73... Ω

venusenvy47• 1 year ago

This is interesting, but isn't this more like a coincidence? Power line engineering and wireless engineering are fairly distinct fields in EE.

cjohnst2• 1 year ago

Coincidence, maybe, but convenient.

That currently may be the case that many or most engineers rarely use both.

But, from a historical perspective, when power generation and distribution were new, there was probably not such a distinction.

Even today, large industrial users of power need to know and understand the types of equipment they're using, impedance and power factor of them, and the aggregate effect on the power grid, and adjust for it.

I imagine that many of the early large users of power were radio broadcasters.

There was likely significant overlap of power engineering and wireless broadcasting. An engineer would need to understand what effect the broadcast system was having on the grid and adjust for it. Calculating the impedance of the entire system using ω and the associated capacitance and inductance of portions of the system. The broadcasting antenna would certainly be a part of calculating power draw and power factor.

kalleboo• 1 year ago

I'm not an electrical engineer so what makes integer 377 easy for mental calculations?

It's seems like 50Hz would be even more convenient because ω = pi*100

Aloha2• 1 year ago

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.

alana314• 1 year ago

As a result I hear B0 everywhere, in power lines, electric arcs, industrial motors, speaker buzz, etc

fahrnfahrnfahrn• 1 year ago

My digital guitar tuner oscillates between B and A# with no input.

throw0101c2• 1 year ago

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.

netfortius• 1 year ago

From a practical stand point, as someone who moved from the US to Europe, and was forced to leave a lot of appliances behind (not because of voltage - that could have been addressed!), f*ck this!

comrade1234• 1 year ago

I moved to Europe too. I have a few transformers that let me use my expensive American kitchen equipment (angel juicer, kenwood giant mixer, etc) here. Slowly I’ve been getting rid of the American equipment and replacing it with European as it’s obvious that I’m not moving back.

jccalhoun• 1 year ago

This reminds me of Wahl clippers that are designed for 60hz and won't work as well for 50hz. https://youtu.be/sZndZhK4Wuc?si=7JJlttjbzVGRb2mB

layer82• 1 year ago

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.

mrb• 1 year 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.

hcarvalhoalves• 1 year ago

Also 5400rpm HDDs were common – that would be 1,5x factor.

emmelaich• 1 year ago

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• 1 year ago

5400 is (was?) very common RPM for laptop HDDs.

Tempest19812• 1 year ago

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.

arcanemachiner• 1 year ago

I see it, but only in my peripheral vision. Drives me nuts.

hunter2_4• 1 year ago

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?

sathackr2• 1 year ago

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

lutorm2• 1 year ago

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.

geor9e• 1 year ago

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.

SoftTalker2• 1 year ago

10k RPM also not too uncommon.

lutorm2• 1 year ago

Did European hard drives run at 3000 rpm then?

jhoechtl• 1 year ago

alexjplant2• 1 year ago

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_4• 1 year ago

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)!

https://en.wikipedia.org/wiki/44,100_Hz#Origin

anticensor3• 1 year ago

Why couldn't they make use of a sampling rate with five samples per frame (which would exactly give 88.2kHz by the way)?

alexjplant2• 1 year ago

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.

aetherspawn• 1 year ago

50 factors

1 2 5 10 25 50

60 factors

1 2 3 4 5 6 10 20 30 60

Seems for AC 60 is overall more flexible in design of AC motors, transformers and other resonant devices

Dylan168072• 1 year ago

Only if you need to align to a second for some reason. 50Hz is still 60 cycles per something.

gorfian_robot2• 1 year ago

relatives living in Australia (a 50Hz county) but with family in the US decided in their new home to provide both 50Hz power with Australian style outlets and 60Hz with US style outlets since many household appliances are much cheaper and diverse in the US. since they built the place with a solar/battery system it wasn't too big of a deal to use two different inverters for the AC side of things.

cwmoore• 1 year ago

"Effects of a 60 Hz Magnetic Field Exposure Up to 3000 μT on Human Brain Activation as Measured by Functional Magnetic Resonance Imaging"

2015

Alexandre Legros, Julien Modolo, Samantha Brown, John Roberston, Alex W Thomas

https://pubmed.ncbi.nlm.nih.gov/26214312/

mrlonglong6• 1 year ago

All that's academic now we have power supplies that are capable of handling both frequencies and the various voltages in use across the globe.

The origins of 60-Hz as a power frequency (1997)

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