Where can I find cheap Active Harmonic Filters (AHF) - Page 1
Forum section: electronics / beginners

author: doodlejump53
author_rank: Newbie
timestamp: July 24, 2023, 01:12:59 am
content: Hi there.Im currently looking for cheap active harmonic filters but all I can find is AHFs that cost thousand of dollars for industrial applications.I need one because my mains line is full of harmonic garbage that causes serious problems with my electronics (most importantly PC), my loads don't consume more than 200W max really.Yes I am aware that there are passive filters, I want full removal of any unwanted harmonic in my mains system and thats just not a convenient for me.I dont wanna have to play around with a passive harmonic multiple stage filter to avoid resonance and still have the added power consumption and everything.The active harmonic filter is supposed to inject the equal and opposite-phase harmonic current into the mains line to cancel out any harmonics.I tried searching cheap for AHFs everywhere. Amazon, Ebay, aliexpress, I even used multiple search engines but nothing.I would appreciate it if anyone can link some sites where I can find cheap ones.I'm even willing to spend a few hundred dollars for one but some transistors and control chips on a pcb shouldn't cost that much.Help is appreciated as always <3

author: MrAl
author_rank: Super Contributor
timestamp: July 24, 2023, 05:24:03 am
content: Quote from: doodlejump53 on July 24, 2023, 01:12:59 amHi,What exactly is generating the harmonics? See if you can pin it down to one device.

author: doodlejump53
author_rank: Newbie
timestamp: July 24, 2023, 06:45:09 am
content: Quote from: MrAl on July 24, 2023, 05:24:03 amDozens and dozens of non linear loads that are very near me that mess up the wonderful clean mains line I once had...I cant really do anything about it tho, since its not even my loads. They belong to someone else.

author: Jeroen3
author_rank: Super Contributor
timestamp: July 24, 2023, 06:56:06 am
content: Quote from: doodlejump53 on July 24, 2023, 01:12:59 amUhh, you want to take on your whole residential connection? Then you need some beefy >50A IGBT's and some fancy realtime control circuitry.I only know of AHF for big stuff. Where standard copper would go into high losses.I think it's cheaper to get a line reactor and an standard LC filter.The line reactor will convert harmonics below <100 kHz to heat, and the filter will remove >100kHz.Or you put some of your critical loads behind a dual-conversion UPS?What equipment is sensitive?

author: dobsonr741
author_rank: Frequent Contributor
timestamp: July 24, 2023, 06:58:35 am
content: QuoteHow do you know the harmonics are your problem? What level of harmonics suppression is good enough for you?Perhaps tell more about the original problem you are solving.

author: Doctorandus_P
author_rank: Super Contributor
timestamp: July 24, 2023, 10:42:30 am
content: Quote from: doodlejump53 on July 24, 2023, 01:12:59 amYou flag suggests you are from Namibia.Please stop this "equal and opposite" nonsense. It is something that the USA folks learn in pre-school. I guess it is because it sounds fancy.However, vectors can not be equal and opposite at the same time.Quote from: https://en.wikipedia.org/wiki/Euclidean_vectorAbout the filtering...I don't know how bad the power situation in Namiba is. Do you have any idea of the frequency content you want to filter? My first try would probably be to just start with an industrial filter designed for use in frequency inverters. they are cheap standard components, and I'm guessing it's likely enough to work to give it a try.

author: Terry Bites
author_rank: Super Contributor
timestamp: July 24, 2023, 12:25:35 pm
content: Equal and opposite is a common phrase in english.Be kind to all and especially to people who are not first language english.And especially kind if you're not first language english.

author: MrAl
author_rank: Super Contributor
timestamp: July 24, 2023, 12:45:15 pm
content: Quote from: Doctorandus_P on July 24, 2023, 10:42:30 amHi,I think most of us here understood what he meant.Equal amplitude, opposite in phase.Whether or not that is a good solution is still to be determined though.

author: bdunham7
author_rank: Super Contributor
timestamp: July 24, 2023, 01:14:41 pm
content: Quote from: doodlejump53 on July 24, 2023, 01:12:59 amThe device you describe would typically be used in an industrial setting to compensate for harmonic currents drawn by a specific device or perhaps by the whole facility. They typically work by actually measuring the input current of the device or system and then correcting that to be an in-phase sinusoid. The reason for having it is similar to the reasons for having VAR compensation devices at the fundamental frequency--industrial users may be charged extra or even disconnected if their overall power factor is too low. Thus these are typically heavy-duty industrial devices that cost a lot of money. There really isn't any reason a consumer would want one since they typically aren't charged extra for poor power factors.What you are proposing is quite impractical because you would be doing it backwards and correcting the entire mains input and not your load. So your device would have to supply hundreds or thousands of amperes of harmonic correction currents, depending on the source impedance of your mains power connection, and it would have to guess at what those currents should be because you don't have access to measure them.If you really want to clean up your power you would either need something like a double-conversion UPS or else a filter that increases your source impedance and then an active filter to work only behind the filter. I'm not aware of any inexpensive consumer products that do either of these things.A good PC PSU should be able to handle some pretty terrible harmonics without any issues, especially if you use them conservatively at 50% or less of their rating. If you have issues, perhaps start with looking at your PSUs. Or give use more details about how bad your power is.

author: CaptDon
author_rank: Super Contributor
timestamp: July 24, 2023, 01:17:32 pm
content: Since most computers have a SMPS which usually rectifies the A.C. mains and powers from that D.C. source I doubt if mains filtering will solve any of your issues? Most likely good shielding of inter-connects between computers will be a better answer. UPS units made by Best Power offer good filtering while in standby and good sine wave output on most models. How bad are your power line 'harmonics'? I have run computers in factories where the power was beyond horrible with no problems. Sola ferro-resonant units can help, but run hot at light loads and if the line frequency varies you will induce horrendous voltage changes in the output. Ferro resonant makes for good filtering and regulation but is very intolerant of frequency shift from engine-generator rpm shift during load spikes.

author: doodlejump53
author_rank: Newbie
timestamp: July 25, 2023, 09:52:38 pm
content: Quote from: Doctorandus_P on July 24, 2023, 10:42:30 amIm actually from the netherlands, not from some african state.I picked that one when I registered my account on accident and forgot to change it, thanks for mentioning it tho lol.The equal and opposite thing is what I found in some documents about the topic via google and even chatgpt gave out an answer containing that phrase.I tried HF EMI filters, pretty much everything that I could find on the market. Pre build ones with inductors, even homemade ones with capacitor shunts with capacitance values ranging from 100nF-30uF all with special X1/X2 EMI Capacitors.But all did very, very little to nothing.I probably spend hundreds of dollars just on those filters that didn't do anything in the end.Also tried toroidal ferrit cores, big ones, smaller ones around all of my cables and it did... nothing...I then came to the realization that it could be harmonics, called an electrician, he analysed my line with a mini oscilliscope and some kind of harmonic meter.My line at that point was full of mainly 3th and 5th order harmonics and also some other harmonics from 10th- 30th but mainly the 3th and 5th.So I assume that those harmonics for some reason dont get filtered out because of some unwanted resonance which causes the previous normal EMI filters to let the harmonics go through perhaps?My PC and other electronic devices dont work right my apartment.My PC for example has severe performance problems that were non existent a few years ago.Severe inconsistent lags, input lag and stuttering, everything you can think off.The normal EMI filters did not change that.The PC is properly grounded, I tested it and made sure of that.And no its not my PC or some components. Most parts are actually brand new including the PSU. Its not some non brand from china or something.I Tested my PC and other stuff at a friends home a few Kilometers away and they ran and still run perfectly with no problem whatsoever there.Other people from other forums exactly have the same problem as me. Im not sure if Im allowed to mention the other forum tho.The mains elecricity should actually be not that bad in my area, a neighbour who lives around 50m away from me never had a problem, doesn't run any kind of filters and never had such issues.Quote from: bdunham7 on July 24, 2023, 01:14:41 pmI actually also already used a normal UPS for my PC, the severe performance, input lag, stuttering problems still occured tho, and yes I even disconnected the UPS from the mains socket to be extra sure. It did also nothing.Would a AHF really use thousand of amps if its just a few non linear loads (without my PC) that consume perhaps less than 700W?I read that a AHF is actually more efficient than any passive harmonic filter, unless I got something wrong.But alright, I'll try out a passive harmonic filter first and see how that works out and if it makes at least a bit of difference.I also ordered a Oscilloscope to be able to measure any kind of EMI/ harmonics myself so if nothing works, I'll get back to you and let you see exactly whats going on my mains line.And btw. I also did the test that someone else recommended on the other forum where you connect a big linear load (2500W heater for example) to the same wall socket as your PC to reduce harmonics.EatenVideos also made a video about reducing harmonics with linear loads on youtube explaining why it works and it actually DID work for me.It didn't solve the problem completely for me but it did help a lot.But its obviously not a permanent solution, I cant have a 2.5 Kw heater running all the time just to use my PC.

author: coppercone2
author_rank: Super Contributor
timestamp: July 25, 2023, 10:00:23 pm
content: its not made because anyone serious about it would put it on a mechanically isolated generator (RF LAB) rather then fuck around trying to clean the power company. Its infinitely cheaper and cleaner.You low balled the SHIT out of your solution.That might be used if there is some crazy specific heavy ass piece of equipment making a problem (think of like a steel mill, pipe maker, chemical plant, etc). They would try to replace it first. I suspect it might be used because it might be smaller then the passive solution, and they probobly have a super cramped electrical system in a place where they would use it.I suspect you would need the USS enterprise (under picard mind you, not kirk) to have this technology available in the way you are thinking about it. That's probobly half of le forges job.Its also probobly super less reliable then a mechanical converter. They are small/cheap enough for a small business.In most cases you would complain to the manufacturer to put a PFC on the equipment. I mean this is stuff like keeping legacy 1950's esoteric heavy machinery in bad places online.

author: CaptDon
author_rank: Super Contributor
timestamp: July 25, 2023, 10:08:42 pm
content: You just answered your own rediculous senario!!! You unplugged the UPS from the mains and it made no difference. Your computer didn't act like this YEARS AGO??? How old is the P.O.S.? Time to upgrade the computer not your power company. Seriously, this sort of troll will require a bigger trolling motor. My 486 laptop seems to stutter and be slow on the inputs and is nearly useless on the internet, you best bet I'll be calling the power company tomorrow to complain about my harmonics.

author: coppercone2
author_rank: Super Contributor
timestamp: July 25, 2023, 10:09:15 pm
content: as for your computer, this almost certainly sounds like a failing power supply, bad power converters on motherboards/cards, etc.It is absolutely the most backward solution possible to the problem that you have to do anything to the power line. Computers are rather unreliable crappy devices.But haha man if you put some crazy shit in front of the PC to keep some $50 broken power supply working that is absolutely hilarious. Kinda like the mayor shutting down the high way because he does not want to fill a pot hole on the off rampthis almost seems like a way to fraud the power company so that you can list some crazy shit they put in your house on craigslist.Does anyone have any ideas on how to get the water company to pay for a satellite uplink? the water line is causing telluric interference to my dish net. send a hydrologist, a priest and a seismologist to diagnose the issue!https://onlinelibrary.wiley.com/doi/abs/10.1002/9781119019213.ch21

author: bdunham7
author_rank: Super Contributor
timestamp: July 25, 2023, 10:36:01 pm
content: Quote from: doodlejump53 on July 25, 2023, 09:52:38 pmIt's extremely unlikely that 3rd and 5th harmonics would cause that. Other interference possibly, but not too likely IMO.QuoteIs this a pure sine wave UPS or a modified sine wave type? Can you provide the exact model? And do you mean the PC worked normally with the UPS unplugged or still had the same problems with it unplugged? Finally, what exact PSU are you using in your PC?QuoteYes, because using it the way you propose--to clean up yourincomingpower--requires you to supply current sufficient to offset the harmonics generated by all the other customers, not yours. The heater thing is interesting because it would lower the source impedance of your power supply, but it should be by a trivial amount. Given all you have going on, I would guess that your issue is not 3rd and 5th harmonics on your incoming power (those are very common) but rather something generated by one of your pieces of equipment. If the problem persists when connected to a pure sine wave UPS with its cord unplugged, you end up with no other possibilities.

author: dobsonr741
author_rank: Frequent Contributor
timestamp: July 26, 2023, 05:25:40 am
content: Is it the harmonics or perhaps surges/spikes?

author: dmills
author_rank: Super Contributor
timestamp: July 27, 2023, 08:54:21 am
content: Third and fifth?I have a lot of trouble seeing a switched mode supply of the PC sort caring AT ALL about that, they are everywhere.Never assume the mains is a nice sinewave, it is safer to assume that it is a mess of harmonics, spikes and all sorts of other rubbish, and sane power supply designers (which is most of them) understand this and design gear to work just fine in spite of the reality.Further the fact that it exhibits the same issues when running on UPS from the battery (with the mains disconnected) discounts the possibility of a mains issue completely.Some cheap PC supplies actually make the problem worse by NOT doing FPC and thereby only drawing current near the top of each cycle which produces current harmonics, but for an individual PC that is small enough for the grid equipment to cope with.AHC comes in when you have an office building full of cheap assed PCs and screens all producing current harmonics and having poor power factor, or possibly something like a theatre where the load varies by orders of magnitude second to second and most of it is phase angle controlled dimming, under these conditions AHC reduces the surcharges you get hit with for power factor and is thus economically viable.The reason third and fifth are not easily filtered is that they are less then a decade above the line frequency, which is pretty negligible, 150Hz and 250Hz respectively, you need a massively complex LC mess to clean that up while having a low impedance output.The common line filters generally start to do something at 100kHz or so and are aimed mostly at reducing conducted emissions FROM the power supply in the 100kHz to 30MHz band where these are regulated by the rules on electromagnetic compatibility.Good odds however that the mains harmonic content has NOTHING to do with your poor PC performance, it would be about the last place I would look. Personally my starting point would be flatten the disks and reinstall everything including the OS, old Windows is notorious for slowing down over time for no very obvious reason (And yes, doing this is a pain in the arse).Looking at the hardware, make sure the fans are running and that the heatsink is not full of bum fluff, the machine will throttle aggressively if the cooling is not up to snuff, MAYBE replace the thermal paste if the system is reporting as high CPU temperature, but that tends to be a messy, annoying faff, so only do if needed.Finally, if that doesn't sort it then it might be time for a new power supply, but issues there generally show up as crashes under load).

author: Jeroen3
author_rank: Super Contributor
timestamp: July 31, 2023, 02:21:25 pm
content: QuoteThose are very difficult harmonics to filter out. Almost impossible, you really need copper and iron for that.Did the electrician make an power quality report? The grid company is required to provide you with clear power up to a certain degree.They monitor this.https://www.netbeheernederland.nl/spanningskwaliteit/metingenAlso, your pc's ATX supply creates some of those harmonics, 3,5,7,9,11.Filters you can lift with one hand only work above several kHz and mainly filter conducted EMI emissions, not power harmonics.Your ATX supply should also not be bothered by those harmonics, unless they are common mode (very unlikely).

author: jmelson
author_rank: Super Contributor
timestamp: July 31, 2023, 03:41:30 pm
content: I have a CNC milling machine in my shop. It is run by a higher-end Dell desktop computer. It has a set of interface boards to connect to the servo drives. It also has a VFD (variable frequency drive) that produces a lot of electrical noise. The computer ran fine, but the servo interface boards would occasionally lose sync with the computer. I put a big line filter module on the power input to the VFD and all was then fine. At a previous time, I had hash on the computer screen from a previous VFD, and a line filter solved it.Jon

author: dobsonr741
author_rank: Frequent Contributor
timestamp: July 31, 2023, 06:55:57 pm
content: Do we still need to focus on harmonics and filter when OP telling the PC issues still happen when on UPS and no connection to mains?QuoteOr perhaps the PC needs a different king of troubleshooting advice?

author: 5U4GB
author_rank: Super Contributor
timestamp: August 05, 2023, 09:37:53 am
content: Quote from: bdunham7 on July 24, 2023, 01:14:41 pmDepending on how messy the input is, using a double-conversion UPS mostly as a power filter rather than a UPS can end up as a very expensive way to turn high-power switching components into short or open circuits. Not that I've ever done this or anything.Maybe I'm missing something here but wouldn't a sine wave tracking filter handle this? A proper one for industrial applications, not the woo-woo sold to audio enthusiasts.