EEVblog #1284 - How Bad Product Design Kills The Environment

[Bud]

As noted in Dave's video, photoelectric detectors detect visible smoke.  Those based on radioactive sources produce ions in the detection chamber which produce a current between two charged plates.  Particles, including those to small to see, in the air decrease this current.  That's why I replaced the ionization detector nearest my kitchen which would often alarm when we were cooking with a photoelectric one.  No more false alarms.

Ionization vs photoelectric alarms serve specific use cases. Ionization ones better detect flames and photoelectric ones are for smoke. They should be used based on risk of type of fire.

[DBecker]

Capacitive reactance is a benefit to the grid, not a negative.

The grid is generally inductive, not capacitive.

Back in the "good old days" (which were never as good as memory suggests) the grid was dominated by inductively reactive devices, mostly lightly-loaded motors.  Large capacitor banks were added in industrial areas when the power factor was absurdly bad, but that wasn't cost effective when the power factor was only modestly bad.

Even in a present-day residential area it's quite unlikely that capacitive supplies come close to locally compensating for refrigerator, fan and compressor motors.

Many areas have a requirement that smoke alarms et al (fire, monoxide, fume) both be wired to the grid and have battery backup.  This is because of the perceived risk that a battery-only alarm won't have its battery replaced.  The requirement has a high lifetime cost with marginal benefit, since hard-wiring costs $50-$250 per location.  The same people that wouldn't replace a battery in a battery-only alarm will just unplug the dual-power alarm when its battery dies.

[rrinker]

 I'm pretty sure it's a requirement for new construction, and has been for a number of years now, but I don't think there is any requirement for it in existing structures. In my area I don't even think they REQUIRE you to have smoke detectors, at least in single family residences, but you're pretty stupid if you don't.

 One thing the hard wired ones buy you, they usually have an extra wire which gets run between all units, so that when one trips, they all sound off.

[coppice]

Where have you seen companies charged for kVA? Around the world. commercial users are normally charged for actual consumed (i.e. active) energy. In some places a commercial user's reactive power or power factor is measured continuously, and if its really bad (or sometimes if its really bad specifically during peak hours) the customer is charged a punishment factor on top of their active energy, to encourage them to improve their power factor.

This is Croatian power company price list for industrial consumers:
https://www.hep.hr/ods/korisnici/poduzetnistvo/tarifne-stavke-cijene-161/161
The table is an image so it won't translate, but the column "Prekomjerna jalova energija" (excessive apparent power) is what we're talking about.

Also this:
https://translate.google.com/translate?sl=auto&tl=en&u=https%3A%2F%2Fwww.hep.hr%2Fods%2Fkorisnici%2Fsavjeti-kupcima%2Fnaknada-za-prekomjernu-jalovu-energiju%2F579%23
Basically, if the customer keeps their power factor above 0,95, there is no penalty. If it drops below it, then there is a penalty.

Demanding the power factor always stay above 0.95 is stricter than the schemes I've seen, but this is basically what I said. Customers are not specifically charged for VA. They are charged for actual watts, and incur an additional penalty if they don't keep their power quality within defined limits. Another interesting power quality related thing you'll find in some commercial tariffs is payment for only the fundamental power consumed. This is related to neighbouring customers having poor power factor loads, since they cause excessive resistive voltage drops, which results in substantial THD In the supplied voltage waveform, and hence harmonic energy.

[DBecker]

I'm pretty sure it's a requirement for new construction, and has been for a number of years now, but I don't think there is any requirement for it in existing structures. In my area I don't even think they REQUIRE you to have smoke detectors, at least in single family residences, but you're pretty stupid if you don't.

 One thing the hard wired ones buy you, they usually have an extra wire which gets run between all units, so that when one trips, they all sound off.

The requirements for alarms vary considerably by region, and even between towns.  In California they are stricter for rental units than owner-occupied homes.
Here interconnection of hard-wired units is required, but my impression is that there is lots of cheating on this point.  The extra conductor doubles the cost of the power cable (NM-B 14-2 to -3) so it's only installed if they know the AHJ inspector will be checking.

[hendorog]

Since there are already smoke detectors which last 10 years, I think there is an opportunity to combine that with energy harvesting.

RF or solar, it wouldn't need to snag very much power to remove the battery problem forever.

[HackedFridgeMagnet]

A few things.

Those chips are interesting I didn't know they existed. Looking forward to using the TI chip the next chance I can.

Reading the video title Dave is completely right. The zener based capacitive dropper is extremely inefficient, time to use the latest technology. Even if it is a very small percentage of the grid power, it is an easy fix for the next generation of smoke alarms.

As to the power factor, it may actually improve the transmission losses being a capacitive load while most of the grid is slightly inductive. (edit: Just had a look at some large office power meters, some leading some lagging, residential seems to be a bit random too?)

re: smoke alarm rules. In Australia as usual it varies state to state but these type of rules tend to be fairly consistent across the country.

from: https://www.legislation.tas.gov.au/view/html/inforce/current/sr-2012-140#GS8@EN

8.   Smoke alarm to be mains-powered after 3 years after commencement of regulations

    On and from the standards upgrade day, a smoke alarm that is required to be in place for the purposes of section 36C of the Act must be –

            (a) a mains-powered smoke alarm; or

            (b) powered by a 10-year non-removable battery.

[thm_w]

Big Clive is overly paranoid about poor power factor products, in that he thinks the power company will start charging you the 15VA a 1W LED takes for example. I have yet to see any evidence of this being the case for residential, and as two people have pointed out its probably balancing out the motor loads. Even for industrial, they don't blanket charge you the VA they generally charge a fee.

Anyway, the environmental aspect is still valid. Here is an article that should back up Daves point:

Ergon Energy is undertaking a power factor pilot project with nearly 30 major business and industrial customers in and around Toowoomba.
The aim of the Queensland Government funded project is to use incentive payments to reduce peak demand by a total 4.7 MVA, with subsequent customer savings and carbon emissions reduction.
Improving the power factor of appliances such as motors and other equipment at individual premises will help improve energy efficiency both for the customers and for the Ergon Energy network1.
An appliance with a low power factor draws more current from the available power source than an appliance with a high power factor. The aim is to increase the power factor to 0.9 or more, that is, so electricity use is 90-plus per cent efficient.
For Ergon Energy the success of this project can eliminate or defer the need for new infrastructure such as transmission lines, sub-stations and transformers

https://web.archive.org/web/20140214055620/https://www.ergon.com.au/energy-conservation/demand-management/electricity-demand-trials/power-factor-correction-pilot-project
https://web.archive.org/web/20130903162112/http://www.ergon.com.au/__data/assets/pdf_file/0014/80123/Power-factor-fact-sheet-12mar2012.pdf
https://electronics.stackexchange.com/questions/85291/why-do-power-companies-never-bother-residential-customers-about-power-factors
https://www.powerelectronics.com/technologies/power-electronics-systems/article/21860956/backtobasics-on-power-factor-and-why-we-correct-it

Although they did seem to conflate efficiency and power factor, which is not correct.

[coppice]

Big Clive is overly paranoid about poor power factor products, in that he thinks the power company will start charging you the 15VA a 1W LED takes for example. I have yet to see any evidence of this being the case for residential, and as two people have pointed out its probably balancing out the motor loads. Even for industrial, they don't blanket charge you the VA they generally charge a fee.

In most countries it is illegal not to base charges on actual consumed energy. These things are specified by WELMEC in Europe, the related OIML in much of the rest of the world, and ANSI standards in the US. Most metrology related to the sale of stuff, from the weight of cheese, to the dispensing of gasoline, to the consumption of electrical energy, follows a tight legal framework in most countries. The requirement to base electrical energy charges on actual consumed energy is a key reason why when there are charges related to power quality issues, like poor power factor, harmonics, etc., these are usually structured as some kind of supplementary fees on top of the tightly controlled charges for actual energy.

[scopeman]

This has been a really eye opening and interesting discussion especially considering the certifications that these devices have to go through. Obviously energy savings was not in the specification.

There was a comment on "rolling your own" better power supply which I agree with from a designers perspective, but lets say you do that and something goes wrong and it fails and burns your house down.

Then I wonder if that would void your home insurance policy? Just a thought.

I do agree that we should demand the the designers do better than what I have seen here. Seems like that bad design should create a market for good design.

Sam
W3OHM

[EEVblog]

I think you should review how reactive power works. The 100MW is not generated by the wind turbine. You generate 5MW by the wind, and place a compensation on the power grid, that will generate the reactive power. It is just a big capacitor. The grid already has a bunch of inductive load, because of motors.

See my comment above.

Nope. Nandblog is right. Your reasoning doesn't make sense. If you input 100MW into 5 million devices then each device would dissipate 20W and -given the parts inside- something would go up in flames. But that isn't happening.

Of course it's not happening. Any potential extra power above what I calculated above (and as measured in W) is dissipated outside the smoke alarm in the form of I²R losses in the system.
It doesn't have to be 100MW, that's just the theoretical worst system case. If the current is compensated for and filtered (for harmonic based PF) then it will be lower. But the fact is that 80mA is real current from the grid, it doesn't magically vanish.

[DBecker]

I do agree that we should demand the the designers do better than what I have seen here. Seems like that bad design should create a market for good design.

It's a nice concept, but there is no market feedback about crappy power supplies.  With complex products it's one spec among thousands, most of them not revealed.  You can't make an informed decision, you can't even get most info before buying and tearing it down.

While government regulations such as Energy Star are intrusive interference in commerce, and I feel I should oppose them on pure philosophical grounds, they are the only way to get the market to switch to efficient power supplies.  Just like safety standards, if there are not enforced regulations some companies will build the cheapest possible product even if it's dangerous for consumers.

[EEVblog]

For those who think this bad PF can be corrected by the motors in your home etc, think again, this is the current waveform.



The poor PF is caused mostly by the terrible harmonic content, that cannot be just lag/lead corrected out, it needs to be filtered out. I believe this is done in stages in the grid, but someone mentioned in the Youtube comments that it's not done until the 110kV stage of the transmission system. This means huge I²R losses in the grid up to that point.

[EEVblog]

Bonus screenshot:

[floobydust]

I worked in the utility industry and big scale power factor correction was rare.

One substation 144kV to 25kV (going from transmission to distribution system) with a couple 40MVA transformers. The system is overstressed mainly due to the largest loads being inductive with a lagging PF, loads that have ever increased as businesses and the city expand. Big electric motors in plants. Upsizing to 240kV lines is ultra expensive due to changing all connected substations equipment to support the higher voltage class, land owner disputes etc. due to the bigger towers.

The usual patch is to crank up the system voltage, for the resulting lower current on the power lines and transformers, so they are not as stressed. But this has limits.

It was decided to install 20MVAR capacitor banks on the 25kV bus to help the power factor. The price for capacitor banks, 34.5kV vaccuum circuit breakers to switch-in on zero-cross, and all the SCADA equipment was over $2M. Just too expensive to be commonplace and they weren't so reliable, the capacitors failed. They experience very high ripple current and lots of transients. Was it a decent solution? It bought the utility a few more years.
Power quality is degrading, demand is increasing and the utility infrastructure is boxed in.

[Ed.Kloonk]

Bonus screenshot:
(Attachment Link)

The old Audio engineer in me goes... farken Hay Zues.

Introducing this into to power is like putting fluoride in the water. (it turns the frogs gay!)

[floobydust]

Is there a DC offset? The scope is AC coupled yet the trace is up. Audiophools are worried about it and AC-couple mains into power amplifiers, seems a bit overboard. https://sound-au.com/articles/xfmr-dc.htm

At the coal-fired power plant 430MW the generator sound is a nice pure sine hum. Further away you go on the grid, those harmonics make transformers growl quite loud.
Most of my equipment buzzes during the day when power quality is worst and go quiet at night. Even LED light fixtures run noisy with dirty power.

I notice mains transformers really don't work well with flattened sine waves, their regulation seems to degrade?

[EEVblog]

Is there a DC offset? The scope is AC coupled yet the trace is up.

The scope is DC coupled.
Although I am a bit perplexed why the negative half current is the same as the positive half current. But kinda makes sense in that the zener is just a diode in the half cycle, and sensor circuit is doing whatever
all the time to generate that crap.
BTW, the other Quell brand is near identical.

[jackbob]

Hello Dave! It's Jacob from the comments section of the video. Thanks for posing this, it looks exactly as I thought it would. This is perhaps worthy of another video. The harmonic content here is horrendous, this is what is causing the poor PF. This is also the worst type of poor power factor not only because it's difficult to correct, but because it causes interference and a host of other noise-related issues. As I stated in the comments section it can be corrected with filters in the power system but these are usually not found until a transmission substation after all the losses have occurred.

Here is a quick wikipedia page describing the components which will ultimately end up removing the harmonic content. The line reactor section describes the use as harmonic filters.

https://en.wikipedia.org/wiki/Current_limiting_reactor

Why does harmonic content create low PF??
Most people are familiar with P = Vrms*Irms*cos(theta) where theta is the angle between the voltage and current waveform. This equation holds true HOWEVER it can only be applied (without thought) to pure sinusoids of the same frequency. That means the voltage and current waveforms are of the same frequency and are both sinusoidal. For any non-sinusoidal waveforms such as this current waveform, they must be decomposed into sinusoids using the Fourier series and analyzed using the same equation for every harmonic. I will post an image of this formula from one of my power electronics textbooks.

One important realization is if the voltage source is a sinusoid but the current is not, ONLY the fundamental frequency of the current waveform can draw real power. The harmonics are orthogonal to the voltage fundamental frequency and will never draw real power unless they have a voltage harmonic to pair with. These harmonics do still draw current and contribute to the overall RMS current draw. These harmonics of different frequencies are responsible for the apparent power draw and the power factor is calculated using its fundamental definition PF=P/S. This is how PF must always be calculated for non-sinusoidal waveforms. P = Vrms*Irms*cos(theta) WILL NOT work in this ball field. Therefore adding inductance or capacitance to compensate for the PF will not work, the harmonic content must be filtered out.

This one of the reasons is why there is generally so much regulation on harmonic content. If these power supplies were a little larger (say for a TV or PC) they likely would not be permissible by many regulating entities with harmonic content of this magnitude.

[nctnico]

I think you should review how reactive power works. The 100MW is not generated by the wind turbine. You generate 5MW by the wind, and place a compensation on the power grid, that will generate the reactive power. It is just a big capacitor. The grid already has a bunch of inductive load, because of motors.

See my comment above.

Nope. Nandblog is right. Your reasoning doesn't make sense. If you input 100MW into 5 million devices then each device would dissipate 20W and -given the parts inside- something would go up in flames. But that isn't happening.

Of course it's not happening. Any potential extra power above what I calculated above (and as measured in W) is dissipated outside the smoke alarm in the form of I²R losses in the system.
It doesn't have to be 100MW, that's just the theoretical worst system case. If the current is compensated for and filtered (for harmonic based PF) then it will be lower. But the fact is that 80mA is real current from the grid, it doesn't magically vanish.

But it isn't power. Please think back about how a generator works, the equations involved (induced voltage due to moving a wire through a magnetic field) and go from there. Your numbers don't add up and it is never ever going to be anywhere near 100MW (not even including I2R losses). Just do the math. For starters let your scope multiply the V and I trace to calculate the power and then calculate the RMS power from that. That is the real power and that is what the mains needs to supply.

[jackbob]

But it isn't power. Please think back about how a generator works, the equations involved (induced voltage due to moving a wire through a magnetic field) and go from there. Your numbers don't add up and it is never ever going to be anywhere near 100MW (not even including I2R losses). Just do the math. For starters let your scope multiply the V and I trace to calculate the power and then calculate the RMS power from that. That is the real power and that is what the mains needs to supply.

Not necessarily true. That is the only power the mains needs to supply at your house maybe. But the I^2R losses in the grid are a result of the current not real power. If the PF is really low, you are drawing lots of useless current, in this case due to harmonics. My previous post describes that harmonics will work their way rather high in the electrical system before being suppressed by filters. All this useless current supplying the reactive power is being moved through the transmission and distribution system while creating I^2R losses in the system. These I^2R losses do create real power losses. If the PF is low enough (in this case it was quite low), then you could literally be using more real power (watts) in the transmission and distribution losses than in the product itself. The generator must supply all the real power associated with the device being connected to the grid, not just the power draw measured at the product.

[jackbob]

Also, I have seen some ask in the youtube comments about harmonics created by switchmode power supplies. Many switch mode power supplies today have active power factor correction. Active PFC does a fairly decent job of getting the current waveform to track the voltage waveform, making the power supply appear almost as a resistive load. It is however not perfect, active PFC relies on a boost converter operating at 100's of kHz which creates some harmonics. It should be noted that harmonics this high in frequency can be easily suppressed with a small LC filter at the mains input of the power supply. This is a common component of every switching power supply and can clean up most of the harmonics because of the high frequency. Inductors have a high impedance to high frequency currents and capacitors shunt harmonics well at high frequencies. The harmonic content pictured in the scope image can easily be seen on the same time scale as the fundamental frequency. In fact, the harmonics are multiples of the line frequency. These low frequency harmonics 100's of Hz are much more difficult to filter and cannot be filtered by a small LC filter on the power supply. They are so close to the fundamental frequency that they make their way through the grid with ease.

[EEVblog]

I think you should review how reactive power works. The 100MW is not generated by the wind turbine. You generate 5MW by the wind, and place a compensation on the power grid, that will generate the reactive power. It is just a big capacitor. The grid already has a bunch of inductive load, because of motors.

See my comment above.

Nope. Nandblog is right. Your reasoning doesn't make sense. If you input 100MW into 5 million devices then each device would dissipate 20W and -given the parts inside- something would go up in flames. But that isn't happening.

Of course it's not happening. Any potential extra power above what I calculated above (and as measured in W) is dissipated outside the smoke alarm in the form of I²R losses in the system.
It doesn't have to be 100MW, that's just the theoretical worst system case. If the current is compensated for and filtered (for harmonic based PF) then it will be lower. But the fact is that 80mA is real current from the grid, it doesn't magically vanish.

But it isn't power. Please think back about how a generator works, the equations involved (induced voltage due to moving a wire through a magnetic field) and go from there. Your numbers don't add up and it is never ever going to be anywhere near 100MW (not even including I2R losses). Just do the math. For starters let your scope multiply the V and I trace to calculate the power and then calculate the RMS power from that. That is the real power and that is what the mains needs to supply.

Nope, I repeat my position.
I don't care about the generator, all I care about is the 80mA real rms current that comes from the 240V supply. The 80mA creates in theory real I²R system losses all along the chain, you can't just ignore that, it's not imaginary.
If this is not compensated for then it must ultimately come from a source in order to maintain that voltage.
I said in the video that 100MW is not a real figure, it's hyperbole based on that 80mA current and no correction. I admit 100MW this is not a practical figure.
And we are not talking sinusoidals here.

[EEVblog]

Bonus screenshot:
(Attachment Link)

Turns out all that funny business is not coming from the product consumption, and with a moments thought that is obvious, more investigation required, likely a proby thing.
A pure R-C-Zener circuit should not create that mid frequency stuff, just the front and back porches.



Well this is strange. Using my AIM current probe I get the exact same waveform. And if I bypass the power monitor for mains input I also get the same waveform.
More investigation required...

[HackedFridgeMagnet]

Nice for a video down the track if you could build up those other two solutions (TI and OnSemi iirc?)  and then measure the three different options. Four if you count the full bridge.