The origins of 60-Hz as a power frequency (1997)
ieeexplore.ieee.org
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Actually, still available. Good to have something quieter when performance requirements are not as high.
If anyone here works at a car manufacturer, please try to get this fixed. Apparently not everyone notices.
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?
Rapidly strobing lights (eg. LEDs being PWM'd) mess with this process and cause you to perceive the intermediate images as your eye moves, leading to some weird visual effects. This was a big thing in the early days of DMD projectors, where they projected sequential red/green/blue frames, and while it looked great when you stared at it, any time your eyes moved the whole image strobed with overlaid RGB fields. (more info: https://www.prodigitalweb.com/rainbow-effect/)
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.
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?
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.
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.
> We can get 98% of the light output with 85% of the required wire.
I guess a 12v bulb can survive a much higher voltage than it's rated for (which needs fewer amps for the same watts, so thinner wire) if it's pulsed, like 120v assuming 10% duty cycle, as long as the frequency is dialed in such that the filament is just about ramped up to its rated temperature when power is cut. Very clever!
Must be fancy cars then. All I've ever owned used relays to switch the lights, just straight 12v onto it no pwm whatsoever.
We PWM those now because the PWM drivers are there anyhow, and with a filament, it’s still lit and bright during the off pulses. It’s cooling, but you really can’t detect it.
If we want to “smooth out” the PWM cycles so we don’t see discrete pulses, we need a few cycles (say, 3–5) within that 5–10 ms window. In other words:
For a 10 ms integration window:
3 cycles → f≥30.01 s=300 Hzf≥0.01s3 =300Hz
5 cycles → f≥50.01 s=500 Hzf≥0.01s5 =500Hz
For a 5 ms window:
3 cycles → f≥30.005 s=600 Hzf≥0.005s3 =600Hz
5 cycles → f≥50.005 s=1000 Hzf≥0.005s5 =1000Hz
And yes, what we are now seeing in cars is super annoying. Similar disregardful to user comfort can be seen with HUD displays (at least with Volvo).
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
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.
Nowadays with switched power supplies, this is not a problem any more. Keeping track of 16.7 Hz seems a little easier. Imagine building a numeric display for a power plant operator to see how far off you are.
You could build a display with 3 as the denominator, and a decimal numerator:
| |_ 2.1
| | \ ---
| \_/ 3> 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.
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.
Edit: Paulmann Velora are the expensive lamps at home.
I guess there’s some internal resistance or something, but…
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.
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.
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.
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.
I suspect some beauty products might also use 20A, or in combination easily reach that.
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
4.18 J/g/C * 250g * (1/ 20,000 kJ/s) * 75C = 3.918sOtherwise, you will very quickly vaporize the water near the heater and the resulting lack of contact will inhibit heating the rest of the water volume.
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.
[1]: https://www.cpsc.gov/s3fs-public/Electrocutions-2011-to-2020...
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).
Not sure about US, yet some high current lanes (thinks of threephase ~400V x 36A; IEC 60502-1) in the households are actually made of Al, not Cu. They tend to be underground though, the wires in the walls are still Cu.
Cu is more conductive than Al so an Al wire has to have a cross section area about 1.56 times that of a Cu with the same current capacity.
But Cu is also denser than Al so the Al wire is only about 0.47 times the weight of the Cu wire.
Al is is much cheaper than Cu so the Al wire is only about 13% the cost of the Cu wire.
Here is a table of the conductivity (in units of 10^7 S/m), the density, and the cost of copper (Cu), aluminum (Al), silver (Ag), and gold (Au).
Cu Al Ag Au
Conductivity 5.96 3.5 6.3 4.1
g/cm^3 8.96 2.6 10.5 19.3
$/kg 9.03 1.2 1030 92100
Weight Cost Diameter
Al 49 7 139
Ag 110 12646 97
Au 310 3190000 121* 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.
Short protection at the breaker for every circuit would probably be necessary at that voltage
240v is a good middle ground for safety and power.
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.
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.
Hrm, which country is that? Something between 13 and 16 amps is normal everywhere in Western Europe that I can think of, at 230V.
In Ireland, any random kettle that you buy is likely to be 3kW (pedantically, 2.99kW); you do sometimes see 2.2kW ones, generally _very_ cheap ones.
The Swiss outlets in my recent construction apartment were 8A. The standard allows a different outlet with higher amperage but I only ever saw that in commercial settings, similar to US 20A outlets.
That said, 2.2kW kettles definitely do seem to be more common there than here in Ireland (where 13 amp outlets are standard).
Our electric circuits aren't rated for 13A continuous draw (e.g. plug-in EV chargers should be set to 8A or 10A), but they are fine at 13A for the few minutes it takes to boil a kettle. 2.2kW kettles would be a major drain on productivity: millions of extra minutes spent every day waiting for a cup of tea!
Perhaps electric cars limit their draw below 13A as they're much more likely to be connected using extension leads.
> 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...
The NMEA2000 standard is confined to 12V however, meaning that all boats still need a 12V system as well. Maybe just with DC-DC conversion, or maybe with also a backup battery.
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.
Time will tell!
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.)
One of the best things about living in the UK! https://www.youtube.com/watch?v=UEfP1OKKz_Q
> 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.
The losses over distance thing is the fundamental conflict between desired properties. For transmission you want as high a voltage as possible, but high voltage is both very dangerous and tricky to contain. So for residential use you want a much lower voltage. we picked ~ 200 volts as fit for purpose for this task. but 200 volts has high loses during long distance transmit. So having a way to transform the current into voltage is critical.
Some of our highest voltage most efficient long distance transmission lines are DC, but this is only possible due to modern semiconducting switches.
quadratically
This would be a pretty good approximation of the ratio of transmission lines to transformers.
>Generally, for long-distance power transmission, DC lines can be thinner than AC lines because of the "skin effect" in AC, which concentrates current flow near the surface of the conductor, making thicker wires less efficient; therefore, for the same power transmission, a DC line can be smaller in diameter than an AC line
This is especially a problem at high voltages and currents.
Also, DC arcs don’t self extinguish as well as AC arcs do, so DC arcs are a lot more dangerous and destructive.
It’s why HVDC lines are still relatively rare (and capital expensive), and typically used for long haul or under salt water, where the inductive loss from AC would cost more than the higher capital costs required for DC voltage conversion and stability.
or that it, itself, isn't a consequence of its own series of sunken cost fallacies
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.
Does this help you understand the original commenter's question?
You're asking how high is up.
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.
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.
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.
My grandfather worked in a Chicago office building that had 110V DC service even into the 1960s. He had to be careful to buy fans, radios, etc. that could run on DC.
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.
Almost everything complex does run on DC internally, but you feed those via AC adapters that then invert it to DC. You'd have to get bespoke DC-DC adapters (transformers, really) for everything.
DC (high) voltage to DC would skip the 1st few steps of AC->DC.
I always assumed it was just one induction and transformation step.
Lights, first and foremost. LEDs are DC.
> Almost everything complex does run on DC internally
almost everything runs on either 5V or 12VDC. What you would need are appliances that bypass the wall-warts/adapters and tap directly off DC, but this comes with some significant challenges. I'm already talking way outside my wheelhouse though, so I'll stop before I make a mockery of this topic.
Its very cool as a theoretical exercise and you could probably make a proof-of-concept house, but if you want to live in it and use literally anything non-bespoke, you have to convert DC to AC, which kind of defeats the purpose.
However, if that were worked out, you could have DC plugs in the house for all existing appliances and fixtures, and theoretically you would get a gain on both sides (no inverter, and no v-regulator (or a simpler, less lossy one)).
Then you wire your EV charger and big electrical appliances like stoves, ovens, microwaves, fridges (?), electric boilers, central AC, heat pumps, etc. into that DC circuit.
That alone would switch the majority of your electrical consumption to DC. Maybe long-term, you could have a special DC socket that you plug toasters, kettles, crock pots, vacuums etc in to, if they became available and cheaper.
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.
48VDC inside homes would be enough for most applications except heating and it would be kid-safe.
240V for heating applications.
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.
https://en.wikipedia.org/wiki/North_American_power_transmiss...
They can share power and are somewhat connected with HVDC interconnections however.
So possibly misremembering or fog of war reporting, or perhaps not important enough for the summaries.
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"...
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.
You might be able to trip up a fancy soldering iron where loop bandwidth is intentionally maximized, but I still suspect the first thing to go would be the magnetics on anything with a transformer.
Yes, but not for the reason you'd think: 50 Hz magnetics have to be physically larger to work (peak flux density for a given current is higher), and magnetics are so big and heavy that they're not designed with much margin. So 60 Hz transformers will often not work at all at 50 Hz, and 50 Hz transformers will sometimes perform pretty badly at 60 Hz (though also sometimes going this direction works fine).
I’m seeing more and more EC motors in commercial applications, for things like 2-3 HP fam motors and pumps.
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...
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.
I've always kept an eye out for good papers about the effort to convert, but they're hard to find.
here is a well animated video about it: https://www.youtube.com/watch?v=DyqjTZHRdRs&t=49s
So he can do exploratory electrical science and analysis with flexible cases?
And PAL got a higher resolution thanks to it.
With 50 cycles/second you would need both divide-by-50 and divide-by-60.
> [5] L.B. Stillwell, ”Note on Standard Frequency,” IEE Journal, vol. 28, 1899, pp. 364-66.
That's 126 years ago.
2015
Alexandre Legros, Julien Modolo, Samantha Brown, John Roberston, Alex W Thomas
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
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
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.
It's seems like 50Hz would be even more convenient because ω = pi*100
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.
The electrical grid is a bunch of heavy spinning motor-generators that are electrically connected to heavy spinning motor-generators and other loads like lightbulbs. The motor-generators are electrically identical, except that we expect to add energy to one side and extract energy on the other*.
So what happens if the energy added by power plants is less than the energy extracted by lightbulbs and the loads on the motor-generators? Conservation of energy means that we must get the energy by slowing down the generators, extracting their kinetic energy. That lowers the grid frequency.
The same thing can happen in reverse to increase the grid frequency. Too much power generation must increase the kinetic energy of the motor-generators.
* Many of the loads on the grid are intentional or unintentional flywheels, so they may actually add energy to the grid if the grid is slowing, increasing stability.
The only thing that matters is that a clock that expects a certain frequency gets that frequency and not 1% more or 1% less.
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
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.
But now? It's pretty much just an implementation detail.
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.