Power Conditioner for dirty grid power?

[Addicted2AnalogTek]

I find myself in need of something to clean up the incoming line AC power from the grid. There's enough HF noise riding on it that it's making precision measurements impossible.  I've gone to the extent of unplugging everything except for an analog and a digital scope and turning off all of the breakers in the house except for one, and it persists.

I've been entertaining the idea of using a pro audio power conditioner since I only need to clean up the power in my lab, plus I'd love to keep the cost down as much as possible, but I don't want to waste my time and money on garbage.

Please help!!!

[T3sl4co1l]

You're welcome to, but what's that going to do about near field induction, and radiation?

Go ahead and use an audio device, but remember if it doesn't come with a spec sheet claiming attenuation under specific circumstances, it's as good as a chunk of wire.

Tim

[Addicted2AnalogTek]

I'm open to suggestions...

[T3sl4co1l]

If you're in a very noisy environment, either consider shielding ($$$), or possibly filing an FCC report (but, I think that only applies if you're a licensed user and the interference is affecting you).

That said, if you're not a HAM, then getting the license, and a radio to try and listen, would be cheaper and faster than shielding a whole room.  Not that the FCC is very prompt about these things...

Tim

[Addicted2AnalogTek]

I'm not a HAM... yet.

There's absolutely no way I'm going to be shielding an entire room, but there's definitely a need for me to do something.  I'm probably just in a really noisy area, but I also know that the grid power here is rather unstable.  There's occasions where all the lights in the house will momentarily dim, and if I'm running an analog scope, the trace will even "dip".   I just need something to stabilize it as much as possible.  Maybe the HF noise is riding on the grid or maybe it's RF interference.  I'm just trying to find something that will not only help stabilize the incoming AC, but maybe filter out as much of the crap riding on the grid power lines as possible.

[hayatepilot]

There are proper power conditioners from EATON and other manufacturers.
Those have proper datasheets and no HiFi-voodoo or snakeoil smell to them. 

But they are not cheap. The smallest one goes for about 600$:
http://powerquality.eaton.com/Products-Services/Power-Conditioning/PowerSuppress100.asp?cx=3

Some UPSs also do some power conditioning. Maybe you can pick a cheap one up from ebay with a weak battery.

Greetings

[filssavi]

If you can see the lights dim it is not only HF noise, you have also a problem with sags, that could very well be a big load getting connected nearby (motor starting typically), to eliminate both problems you could use a good quality double conversion online UPS (the good quality bit is important as cheap ups will have square wave output)

Now that is for conducted EMI

for radiated EMI there is not much you can do other than shielding

[BrianHG]

There's occasions where all the lights in the house will momentarily dim, and if I'm running an analog scope, the trace will even "dip".

When you say occasions, you mean this happens regularly?  This may be a valid thing to complain about to your power company.  A few homes ago, I had only 110v, where there was a center tap problem on the transformer for the neighborhood and anytime someone turned on their AC heat-pump, part of my house would dip to around 85vac until the compressor was spun up which happened regularly in the summer months.  It took a failure of the iffy transformer and once it was replaced, my voltage was a rock steady 126v-124v continuous, even throughout the summer.

Do you have a safe meter with safe probes to measure your nominal AC?  What are you measuring?

[Halcyon]

Some UPSs also do some power conditioning. Maybe you can pick a cheap one up from ebay with a weak battery.

If you're considering a UPS, I'd be looking at an on-line type (in that the inverter is always running from battery and the mains power just charges the battery). You might find that even at low sensitivity levels, a line interactive UPS might switch to battery more often than desired. An on-line UPS also has the added benefit of no switchover time from mains to battery power. They do command a higher price however and don't usually come in capacities smaller than 1000VA.

I'd avoid the "audiophile" stuff. A large majority is just cheap off-the-shelf parts from China that does very little other than glow pretty colours.

[BrianHG]

If you can see the lights dim it is not only HF noise, you have also a problem with sags, that could very well be a big load getting connected nearby (motor starting typically), to eliminate both problems you could use a good quality double conversion online UPS (the good quality bit is important as cheap ups will have square wave output)

Now that is for conducted EMI

for radiated EMI there is not much you can do other than shielding

Yes, a true sine-wave double conversion UPS would eliminate power dips right to the point of 0v for the amount of time it takes to drain the battery.

[BrianHG]

I'd avoid the "audiophile" stuff. A large majority is just cheap off-the-shelf parts from China that does very little other than glow pretty colours.

I don't think the OP can afford an Audiophile grade 30K$US power filter/conditioner.  I don't think such a device has any cheap Chinese parts or glows in any pretty colours.

[Halcyon]

I'd avoid the "audiophile" stuff. A large majority is just cheap off-the-shelf parts from China that does very little other than glow pretty colours.

I don't think the OP can afford an Audiophile grade 30K$US power filter/conditioner.  I don't think such a device has any cheap Chinese parts or glows in any pretty colours.

You would be surprised at what that kind of stuff contains. The price tag means nothing (other than you have too much money). People spend hundreds of dollars (if not more) per metre on HDMI cables which perform no better than the $10 ones from your local office supply store. I once pulled apart an expensive audiofool amp for a mate as it stopped working; my $300 Yamaha was of far better quality.

If I was buying such gear, I wouldn't be looking at audiophile equipment, I'd be going for proper professional-grade equipment used by companies and individuals who know much more than I do.

[BrianHG]

When the conditioner has 2 100 pound split-bobbin transformers in it, mid narrow band 60hz filter and HV voltage regulator, then back down to AC mains and no flashy lights, it's got to be somewhat good at separating you from the mains and voltage regulation.  I don't think the Chinese would take it this far...

If you are paying anything above 200$ for a small metal box that only weighs 5 pounds with a few plugs and lights, yes, it's most likely Chinese crap.

[David Hess]

I use an online UPS to power my workbench and instruments and it works great.  Some like the old Powerware Prestige EXT models operate as line conditioners even without batteries but of course they have a very short holdup time.

[John Heath]

I find myself in need of something to clean up the incoming line AC power from the grid. There's enough HF noise riding on it that it's making precision measurements impossible.  I've gone to the extent of unplugging everything except for an analog and a digital scope and turning off all of the breakers in the house except for one, and it persists.

I've been entertaining the idea of using a pro audio power conditioner since I only need to clean up the power in my lab, plus I'd love to keep the cost down as much as possible, but I don't want to waste my time and money on garbage.

Please help!!!

The problem has not been identified. It is HF for high frequency. This means it is not dirty hydro as HF will not make it through you step down transformer outside your house. You are causing the HF problem. Is it in the air or in the AC plug. Hook a scope probe to a square sheet of aluminum foil. If you see a bunch of noise it is in the air. Replace ceiling lights with old school tungsten lights  . The scope with the aluminum sheet will tell if this is working before changing the other lights. With the noisy light bulb fixed it is 1 down and 20 to go. Next would be switching power supplies. Just about everything has a switching power supply so that fix is not so easy.

[edpalmer42]

Some isolation transformers are designed to reduce both normal and common-mode noise transmission.  One term you'll run across is 'Ultra Isolation Transformer'.  The most important feature is that the primary and secondary windings are wound on different parts of the core instead of being wound on top of each other and there are grounded shields around one or preferably both coils.

Another idea is a ferroresonant isolation transformer.  They sometimes are designed in such a way that they do a very good job of noise isolation.  Unfortunately, that's not a given so it can be tricky to determine whether a given ferroresonant transformer will be good or average at noise reduction.  The fact that it also gives a constant AC voltage out when the input voltage varies is a nice bonus!

[VK5RC]

It might appear a bit off beam but have a good look at your ground, I had no end of trouble with RF noise until I found it was conducted EMI coming via the earth /ground.
SMPSUs are the devil's work from a Ham's perspective.

[Electro Detective]

Yeah, stay well clear of Audiophool credit card surge and brownout  ~power  conditioners~   
and the jargon slinging salestards who would sell their family for a high commission, much less have second thoughts burning your wallet     

If it's not a heavy weight Sola, Eaton or similar ferro-resonant job, or online sine wave UPS,
don't blow your money and prayers on a lightshow equipped placebo-conditioner   

besides the great suggestions above, I would first go through every single power cable, IEC lead, power board etc etc for correct polarity

then check the incoming power sockets, and check that the mains is wired correctly and screws to the breakers etc secure, firm and tight  > wearing gloves, rubber boots, glasses, and with the mains breaker OFF of course   

I would open up the test gear too and ensure they are wired properly and no factory or backyarder tech repair stuffups 

Yes, it's time consuming and may be an exercise in futilty,
but ONE crap cable, poor or reversed connection somewhere in the works can drive you nuts FOREVER... 

and send you to the poor house throwing money at the 'problem/s' 

[Red Squirrel]

Maybe look at a quality pure sine inverter, then connect it to a AC-DC converter, and throw a battery in there for good measure.  Will also act as a UPS.  Idealy you'd want the inverter to be an isolated output.  Kinda hard to know if it is until you buy one though, as that's not really something that would be advertised.

Though for when you absolutely need it clean you could unplug the converter and run straight off the battery.

Downside is inverters/SMPSes may produce some RF noise so you might be fixing one problem and adding another.

[WA1ICI]

Look into the Elgar 6000-series power conditioners.  They have a nice isolation transformer and correct the output voltage by comparing the output to a clean sine wave (derived from the AC input) then using the difference (error) signal to drive a solid-state power amp to boost or buck the output.  It's much more efficient than regenerating the AC power from scratch.  As a test, my 1KVA Elgar 6006B drove a Tek 556 scope (600W of highly non-linear load) and the AC had 0.08% THD at 60Hz.  And no shifting of voltage with changing source or load.

Elgar is long gone, but their manuals are still available on the web.  I bought mine on eBay for about $200, and it worked great.  I bought a second one, and the power transformer was blown  , so be careful.

Most of the audiophile "power conditioners" are little more than filters with MOVs and can actually make the power worse.  However, Accuphase in Japan makes very good conditioners that use the same technology as Elgar.  The models I have investigated are the PS-510 and PS-1210.

- John Atwood

[Addicted2AnalogTek]

Awesome feedback, everyone!!  Greatly appreciated!!

I've been sleep deprived for days and am resting today, but I'll be doing some checks and tests tomorrow to try and isolate the problem. 

Regardless, I want something with a pure sine output and filtering for the bench, and I need to invest in an isolation transformer as well.

-Brian

[sibeen]

I find myself in need of something to clean up the incoming line AC power from the grid. There's enough HF noise riding on it that it's making precision measurements impossible.

Whoa. What does this even mean? How is HF on the incoming mains affecting measurement? What is the amplitude of the noise? What is the frequency? Is it continuous or intermittent or cyclical? Is the noise common mode or differential? Do you have an oscillogram of the AC waveform?

Rushing out and buying a UPS or power conditioner may be a complete waste of money.

[David Hess]

Look into the Elgar 6000-series power conditioners.  They have a nice isolation transformer and correct the output voltage by comparing the output to a clean sine wave (derived from the AC input) then using the difference (error) signal to drive a solid-state power amp to boost or buck the output.  It's much more efficient than regenerating the AC power from scratch.  As a test, my 1KVA Elgar 6006B drove a Tek 556 scope (600W of highly non-linear load) and the AC had 0.08% THD at 60Hz.  And no shifting of voltage with changing source or load.

You can get a used Powerware Prestige for less but the Edgar looks really nice, includes the isolation transformer, and has full documentation.

I doubt the Edgar with that giant class-AB linear amplifier is more efficient than an online UPS as they all use switching stages now but it will be inherently lower noise than a high frequency switching inverter.  Typical online UPS designs now use a boost power factor correction input stage to produce a high voltage DC bus which gets pulse width modulated to produce the AC output.  The low voltage battery bus is separate (but not isolated, careful!) and has its own boost converter so the output stage does not directly run from the relatively low battery voltage.

Do you have any idea why Edgar went under?  I guess power conditioning like that is not a large market.

For my setup I have an online UPS followed by a home made isolation transformer made up of two big identical transformers wired back to back.  I could have used a separate earth ground between the transformers for additional isolation but have not bothered.  A rough 60 Hz passive filter between the transformers would help remove switching noise but that is pretty low anyway.  With an oscilloscope I can see the steps in the sine wave output but no high frequency switching noise.

Ferroresonant Transformers are one option but they have lower efficiency except close to their rated power.  This is especially a problem if the transformer is oversized to handle surge current requirements.

[Stray Electron]

  I didn't read all of the replies so maybe I missed it but what you want is a ferro-resonant transformer, such as those made by Oneac.  They will isolation the input power and will also regulate the output. 

   Few people know what these are so they can be found CHEAP.

[Addicted2AnalogTek]

Those ferro-resonant transformers must be rather weighty!! It appears that the shipping charges for most of them is double the product cost!!

It appears that my issues have been resolved since the power company came by and gave me a new meter!! Maybe what I was dealing with is oxidation or corrosion buildup in the meter socket, creating some very unwanted parasitic effects in my entire house?? After all, the meter housing is quite old and I doubt it's completely water-tight anymore...
I seriously doubt that's going to solve the power line dips, though.  My guess is that these occur when they are working on the lines in my area, which used to be very frequent. I don't recall it happening anytime in the past few months, but that's not to say they won't start working again and give me multiple sags a day for weeks on end....

Those ferro resonant CVTs seem to be the way to go, though!!  The older ones I've been looking at appear to be built rock-solid, and my guess is they're still around for a darn good reason.  I've just been trying to find info on whether the older ones provide isolation or not.  My guess is nay, so one of those will likely take second to an isolation transformer so I don't get roasty-toasty up in here!! I don't really care if the power goes out and my stuff shuts down since the vast majority of my equipment is analog. I'd like to be confident that nothing will go "POOF" if a surge happens, but I've ran two dedicated GFCI circuits with surge protection to my lab area, so nothing like that should happen!!

I think I may have eliminated the need to drop hundreds on unnecessary equipment... especially the sort that would protect a bunch of tube driven and CRT devices... PHEW!!

Thanks everyone for the feedback, definitely very useful information, at least to me!

-Brian