Wattmeters - what's inside, how do they work
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- Опубликовано: 26 сен 2024
- Exploring the mysterious internals of analog wattmeters, explaining their purpose, how to use them and how do they work. What's a real AC power in Watts, apparent power in VA, reactive power (inductive and capacitive), power factor and current phase shift. Briefly talking about digital wattmeters and showing my DIY "digital" wattmeter, with schematic and how does it work.
Power factor meters:
• Power factor meters - ...
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I'd definitely watch any video of yours, even if it's half an hour long, or even more! Your experience level and your talent to explain in an understandble way is truly excellent! You got my patreon support for sure. Thanks for all the effort you put into making such educational content.
I would do the same, easily. Love the long content with more room for extra explanations and examples. Keep it up, DGW.
OUTSTANDING
I couldn't have said it better myself!
As I've said before you have a talent for explaining things. I've been trying to properly understand real/apparent/reactive power for years but most explanations are shallow and don't really explain it well. I understood it fully within a couple of minutes of watching of this video. If you aren't a lecturer in electrical engineering it's a sad waste of your talent.
I also think it is funny (and instructive) that you can explain things better with some scraps of paper and a couple of coloured pens than some people who are using fancy graphics and animations.
Yeah!
I did understand how reactive power works before (even though, I didn't really know how the watt meters worked). But he is probably the first one I see, who is actually explaining how energy is stored on the way up the AC half wave, then released on the way down. Most others I have seen, are just focusing on the phase shift between voltage and current (often with calculations), without any real explanation how that phase shift appears.
In my own case I figured it out (from others poor explanations, haha) by start looking at an ideal a capacitor and looking at the AC as varying DC with changing polarity, rather than AC. When a constant voltage (that doesn't change over time) is applied over a capacitor, no current will flow (easy to understand) - but as soon as the voltage are rising or falling over time, there will be current (is the voltage is rising, the capacitor will charge, if it's falling it will discharge). The quicker it rises or falls, the more current will flow.
The steepest part of a sine wave (where voltage is changing the quickest over time) is right where it crosses zero and the flattest is the top of the waves (for a brief period, the voltage is constant and don't change over time). That's why current is at maximum when voltage is zero and there no current at all flowing when voltage is at maximum (thus creating an offset between voltage and current at 1/4 of a cycle or 90°).
For an ideal inductor, the DC resistance is zero instead (which means there will always be a current if a voltage is applied, no matter how small - but the higher the voltage, the quicker the current will rise over time). This can be taught of as the current being the speed of a flywheel and the voltage a force applied to accelerate/decelerate that wheel.
The current will be at maximum right at the zero crossing, where it have had maximum time to "accelerate". Once the polarity changes it will start decelerate and release energy, towards zero (which will happen right at the top of the wave) and then change direction and accelerate to maximum once the voltage is down to zero again, to then start decelerating again and so on.
Now if a resistor (or other resistive load) is placed in series with the capacitor, there will be a voltage drop that prevents the capacitor voltage from exactly track the AC voltage - thus making the phase shift less than 90° and go more towards resistive than capacitive.
Same for the inductor - it will be like putting a brake on the flywheel (or use it to drive something) in that example (mechanical work will be done instead of the wheel just accelerate back and forth)
@@Speeder84XL We did all this in high-school: were the technical stream would take you through electricity and electronics to a level sufficient to apprentice electrician, upon graduation. The U.S. Navy trained many sailors, just smarter than a bag of hammers, to have a good working knowledge of this stuff. If you were as smart as a bag of hammers, or not quite, you could always be in the U.S. Army. The U.S. Air Force was a lot pickier.
@@willthecat3861 And then there is always some asshole coming up with a comment like this.
I just explained how I got it, like 15 years ago and taught it was (along with the explanation in the video) another good way to "visualize" the behaviour of the voltage/current and why the phase shift ends up at 90° for a pure inductive or capacitive load (and somewhere between 0-90 for a partially inductive/resistive or capacitive/resistive load). I'm not trying to outsmart anyone...
Wow that has to be the best explanation of reactive vs real power. Simple and easy to understand.
Yeah, he explained it very well and in a very understandable way. It even made it through my thick head.
absolutely the BEST explanation of reactive and real power i've ever seen, thank you :) there are so many explanations out there that seem to leave me with more questions than I initially had, but your ability to explain things in such an intuitive way is just brilliant. thanks again and thank you for all your content.
"Who clicks on a video if it's half an hour long". Well, I do. And I do love all your videos irrespective of its duration. I learn a lot from them and appreciate your great effort.
For this particular video, the explanation between 2:35 an 6:17 is one of the best one I've came across so far about this tricky subject. I've never learned it that way and now it makes sense. Thank you so much!
What a beautifully well made instruments! They must have been a huge investment to buy it when a new item! A credit to the designers & the assemblers of the time. The 3 phase mechanism is just incredible. Do not be concerned with length of your videos. You have a gift of being able to hold my attention & make a fantastic explanation, a true teacher! I must show my support for your channel as you deserve reward for your fantastic effort!
I never saw many of these old analog panel power meters; especially the 3-phase ones. I think they were expensive, so only used when there was a real good reason to know the average real power, and hence the electrical energy being consumed. Those Bakelite wattmeter "test sets," and associated shunts, were more common. And I've got one or two. We had them in the undergraduate motors and generators lab, and the utility company troubleshooters had them too.Not sure but, may commercial electricians might of had them too.
@@willthecat3861 yeah and ive seen these laying around in the old abandoned factories around here guess they really think they are worthless now
wow I have never seen any other youtuber being so precise in explanation of electronics or any other field.Wow you must be really good😃
Wow, I never thought it could be possible to build such a thing so easy for real power. Great explanation!
This was an excellent deep dive into a fascinating old-school technology. Thanks for putting in the effort.
Yet another example of why this is such a great channel for learning.
Never really understood the sorcery of Apparent & Real Power but you sir described it all pretty well. Thanks a ton!
Man!! Can't get enough of you videos. Excellent explanation of theories. Million times interesting!!
Holy crap this video is so informative. I've never understood this topic so well.
Every second of it is pure gold!
I will happily watch all of your videos, regardless of how long they are, because there is always so much to learn from you. Make the video as long as you feel it needs to be to convey the lesson. There are those of us that will only get more excited the longer your video is, due to the excellent way you explain everything. Thank you Dany! Fred
We are so lucky to have a great teacher like Danyk.
Great explanation 👍 by far the easiest to understand I've seen.
I watch/listen to uploads 1:30+hrs long. 30mins is a short clip..... Kids today and their short attention spans.
Thank you for showing these vintage analog power meters. Amazing internal mechanics, especially the 3-phase one.
Nowadays, such meter would just contain 3 current-sensing coils, a silicon chip, some support components and a read-out. These mechanical ones are true pieces of workmanship and art.
This is probably the best video explaining what a power factor is and why. Highly recommended. Danyk, great work!
as normal you give us a load of class info. THANK YOU D, YOU NEVER FAIL TO IMPRESS...
Another absolutely superb and insightful video. For way too long I honestly had no clue about how wattmeters measured only real power (or even how they worked). Also a brilliant explanation on reactive vs real power
Nice video! I really like the peek inside the 3 phase mechanical meter 👍🏻 Thank you.
The three-phase wattmeter has an absolutely mesmerizing mechanism. Wonderful mechanical construction. Genius.
I really loved it. The 3 phase wattmeter sound difficult, but it is really not. There is someone probably still alive sitting at home who have calibrated those.
As we progress in the electronics, we loose how we made the simpler instruments. There is thousands of minds behind how to make a digital multimeter. From the silicone up and down and beyond.
There is less minds behind how to make a analog simpler but yet precise and accurate, from metallurgi to the engineering.
I think we need to have the knowledge to step back in the technology advancements. We need redundancy.
Immerwieder gut erklärt.Die alte Technik ist auch immer sehr schön anzusehen, außerdem ergibt sich aus den mechanischen Meisterwerken die Funktion.
I like the "bloody long" videos, Danyk - please keep doing these great videos :)
This was a fantastic explanation of real vs. reactive power (as well as how watt meters work), and a video that was well worth watching. Even if it doesn't draw a ton of views due to its length, just know that your regular viewers really appreciated it.
I always expected your video more than 20min long. ❤️
Very interesting, and what lovely instruments they are especially the three-phase wattmeter. Half an hour is definitely *not* a problem, when you get such a clear and understandable explanation of real power vs reactive power it is time well spent!
30:10 I might not understand completely the details of schematic drawing but I watched it completely. I like the way you explain it. 🙂
Very nice old meters! Thanks for posting this one, very good explanation.
Excellent video, I learn something new every time.
I learn more from diode gone wild than anywhere else. you are awesome...thanks for all the great videos
Videos like this are exactly why I support you on Patreon.
And that 3-phase meter must have been outrageously expensive when it was new.
Hey, thanks for that bit of AC theory :) Builds upon EEVBlog's miniseries on AC, complex numbers etc. pretty nicely.
The wattmeter teardown... I absolutely love it! These old meters are a damn marvel of technology, the build quality is superb although you really need to be careful not to drop one, otherwise it'll probably be done for. Thing of beauty, joy for ever. Which reminds me to make a '60s Polish UM-3a multimeter repair/teardown, haha :)
I teach this stuff to bewildered-looking engineering undergraduates, and this is quite the best description of how power factor works and can be measured, that I have seen. Aslo, that three-phase wattmeter is a miracle of mechanical design! I will be recommending this material to my students.
Another great explanation. Thank you Dany. God bless you!!
This was definitely worth 30 min of my time.
Very good video as always.
Great video.
I love the complexity of the 3ø power meter.
Danke! Thanks!
Nice shown
Nice explained
Very good understandable for me.
Special thanks for the warning of overload in low real Power but high active power operation
Thank you for your detailed and well illustrated explanation. Today I see only digital equipment, and the underlaying magnetic and electric forces are6not visible. Your video makes it visible and understandable in a great way..... I wish in my school times or university times we would have had someone like you as a teacher. Thank you.
Half hour video like this is enjoyable to watch, but then I was born loooong before the www arrived. :o)
That 3 ph meter mechanism is just wonderful - who would (or could) make such a thing these days ?
It must have been expensive back then, it would be priceless now.
Thanks for the effort you put into making this video.
I enjoy the longer videos. your in depth explanation of all the components are great and I definitely learn a lot from your expansive knowledge..Thanks
AC theory is always a great review for electronics. Good job covering this. Phasor review is mandatory.
woooooow that three phase one is insane!
Nice to know more about power factor and different types of loads. Than you!
Great video thank you for the effort, greetings from Bulgaria
So cool that the panel meter uses a permanent magnet and aluminum plate for eddy current dampening! Early phonograph motors and kilowatt hour meters used that same technology although with AC electromagnets.
The people who designed this mechanical stuff to measure power are the real smart ones !....cheers.
I remember in my college electronics course we were taught a saying ELI the ICE man. E for voltage leads current in a purely inductive circuit and I (current) leads voltage in a capacitive circuit.
Yes my friend, a wonderful job of explaining power factors and all without any of the maths.
Who needs to know about vectors, imaginary numbers and the phase angle’s cosine? Not me :-) well done mate, keep up your good work and best of all, you lucky people, including old men like me :-) all get educated and it's all for free.
PS my best regards to the co-star of your show, your wonderful cat, .
after two years of waiting we finally got our videoo
Great explanation 👍
Thanks for sharing ☺️
Excellent video as usual! But to answer your question of "who is going to click on a video if it is half an hour long?" ME ME lol ...I wish they were longer! :)
You're brilliant! Looking for another great videos! Electric/electronic measurement devices are very interesting! Thank you!
Very nice, i like the 3 phase mechanical meter. 👌🏻
I finally understand why PC UPSs, and generators, state VA ratings and not W, after learning about pure and apparent powers
Another great video. It’s fun how ancient electro mechanical technology can do what digital meters do with math. In effect these old watt meters are analog computers. I’m wondering when most public power utilities will start charging based on average current, aka VA, rather than watts. Most loads in homes with gas heating and cooking are non-linear loads. And that includes electric vehicle charging.
Awesome video!
Really interesting to know how AC watt meters deal with reactive power (I didn't really know that before)
Great video, up there with your others that cover strings reactive phrases & rotational dynamics.
But better than the 'ants' video.
Very instructive video.
I really like your long format videos! This one in particular was excellent, and featured one of the best explanations of power factor. Very clear, and easy to follow. I would be curious to see some distorted waveforms through the watt meters to see how accurate they are, maybe hook up some of the cheap SMPS you've explored in the past? And what about half wave rectification? Almost every range hood or range top microwave uses a diode to dim the lights on the bottom. It's effective, but seems like a bad idea to me; plus, it often makes the lights look flickery. Finding LED bulbs to fit in these lights is even harder 'cause the flicker is always very noticeable unless you get a good quality bulb. Bit of a tangent there~
I have a 2000VA transformer made by CKD-Moradny in 1956. The transformer made me realize that Czechoslovakia is a very good transformer core maker, very advanced in metallurgy.
I thought I was pretty good at following people with a heavy accent, but this takes the cake. The video really needs captions.
Nifty powerstrip Watt meter! Though, shouldn't the current shunt be placed before voltage sense circuit? As is, it measures the Voltage losses of the current shunt + the load connected. Personally I'd like to exclude the self consumption of current shunt from metering point of view when used as an investigatory tool.
On the other hand, as-is it will correlate more closely with the house energy meter if the powerstrip is the only thing being "ON" in the house.
Cracking good video for explaining reactive power to people, it is often quite a nebulos subject to understand.
Even though the video was 30 minutes long I never get bored
Impressive that these wattmeters are still pretty accurate after all those years. Any datecode on them? I would guess mid to late 60s.
More like early 50s but they're eastern bloc so they might be later.
I recently did a repair on a Weston instruments variant of this. (damaged in shipping) the suspension on the meter needle and voltage coil was broken. needless to say, these are really hard to get back together once fully disassembled.
very very very very good video ! thanks
Great video. Thank you
I like long videos, prefer them to short ones
Made in Czechoslovakia! So much precision but it still challenges the engineer!
I kind of look for videos that have a length of 30-60 minutes. They are often in-depth explanation of something.
I like your video. I appreciate long video than short once like 10 mins...
briljant explanation - thank you !
If I'm not mistaken the two springs that are used to return the needle to zero and supply the voltage coil are wound in opposite directions, in other words as one spring gets tighter the other gets looser.
Edit. This is for the first wattmeter.
Correct me if I am wrong, but I think that the Watt meter needs spring return, so both springs should pull in the same direction. The cap/ind phase shift indicator shown at the end of the video do not have return spring if I remember correctly, the needle flaps around as you shake it and stops anywhere when not energized.
If you had a hand-cranked alternator feeding into a reactive load, would you be able to feel it getting stiffer over the parts where it is charging the capacitor or building up a field in the inductor, then easier to turn over the parts where the capacitor is discharging or the field is collapsing?
can you plz make videos on radio with old Soviet radio ...bcos they are really cool
I click on long videos. When the video is interesting and/or educational then the time just evaporates.
There is often a resistir parallel to the current coil.
There 02:01 that's only with Vectors, or you can say:
Apparent Pow = sqrt((Real Pow^2)+(Reactive Pow^2))
Or
Apparent Pow = Real Pow + iReactive Pow [with complex numbers].
As usual excellent content. I really need to buy an analog meter. Also I need to get a vacuum tube voltmeter, saw on a Mr Carlson video how amazing some of their input impedances are.
10 Megaohm......und mehr.
I like your long videos👍
Superb, thank you.
finally a video
30:09 Don't talk like this. That was amazing. I really like this video.
very good video!
I watched the entire thing 30 mins & was not board 🤘🏻😎🤘🏻
*bored ?
Thank you
And it's coneeeecteeeeeeeeeeed. The voltaaaageeeeeeeeeeee
I clicked on the video and watched it from the start to finish. Very interesting. Never seen mechanical watt meters. And the three phase one. Man that is some mechanical engineering if you ask me. You should mention the needle counterweights on the voltage coil sticking up from it into the space. Someone may ask what they are and what they do. I send you an email by the way. Want to buy some programed ATMEGA from you. I can not get my USBASP programer working on Win 10. And my current PC doesnt have paralel port to use PonyProg... It sucks...
Can someone explain why devices with rectifiers only draw current at the peak of the sine wave? Because of the following smoothing caps?
I love your videos!
Small question: is it possible to measure the reactive power consumed by supplying the voltage coil through a capacitor to shift the voltage by 90°?
It deserves to be experienced.
those ad633 are expensive. needed one to build a ring modulator and the chip was around 20 dollars. interesting chip though.
awesome as usual , thanks a lot
To by mě zajímalo - co dělájí měřidla (Wattmetry) od výrobce Metra Blansko - tak daleko od domova :-)
Sir can you help me? To measure the amp coming from charge controller I used my multi meter in series but the amp it showing is only 1.3 amp. But the open circuit amp of charge controller is high. Does battery is interfering while measuring amp measurement from charge controller? Do I need to use shunt dc energy meter? I don’t have dc clamp meter. Please answer
nice ... but also wireing the "Kreosan"(-channel) way ...
That 3 phase watt meter surprised me.
Not sure what I was expecting, but definitely wasn't string.
DGW what is the cord joining the three phase one made of? Is it thin wire? It is hard to imagine a 1960's natural or synthetic fibre cord that could withstand the wear and have no stretch (before kevlar).