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  1. #41
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    The inductor goes on the unit input.

    The capacitor goes on the line side (source side) of the inductor, wired across the line.

    Noise comes OUT OF the PP. Simplified explanation... the inductor blocks noise, and the capacitor "shorts out" any remaining noise, with. the result that the noise that is sent down the power line to other equipment is greatly reduced.

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    By wired across the line, do you mean just a regular run capacitor(like what's in the PP) with the 2 connections on top, and one lead goes to each of the 120v/1ph going in? nothing going to neutral/ground, or does it need the caps with the 3 connections on top?
    I really now eff all about how to wire in caps and trying to find pics online or this setup isn't yielding anything. So I might skip that part of the experiment...

    I'll see about changing the filter caps in the 10hp blue unit today, they were testing fine a few months ago and I just keep putting that one off cause they're pretty near impossible to change the way they're blocked by the wire harness in there, no sure what they were thinking there...

    Anyway, if i manage to change them without wrecking anything and it still runs after, I'm gonna see about ordering the line reactor this week, hammond makes a 1ph 240v 10hp size that should work on the 10hp PP.

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    Well, it took quite a lot of screwing around but managed to change the 3 caps in the blue 10hp unit. Getting them out was one thing, real problem started with the new ones being .020" bigger, the old ones were already tight and new ones didn't fit so I had to cut some of the rack away to get them in there. Anyway, powered it up, and it appears to be feeding back less than it was. I can only hear it in the microwave a bit if I put my ear on it, instead of from 2-3 feet away. Old caps were all testing fine though, lowest at 19.3uf but still 10yrs old.
    Maybe I should focus more on putting something the 20hp unit now since changing the caps in that one had made no difference and it is being pushed much harder with the cnc's, than the 10hp running manual machines.

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    it is very possible for capacitors with the same capacitance value to behave differently for this sortof noise issue. Capacitors are not perfect parts. They have some resistance and inductance, which is affected by the internal design of the part. Since the function of a capacitor is to 1) store charge, and 2) pass AC signals through the capacitor, any extra resistance etc can reduce the effectiveness of passing AC signals.

    In a filter, the inductor tends to prevent AC signals from passing through, while the capacitor "shorts out" the higher frequency AC signals, with the result that the filter "removes" the high frequency signals ("filters them out"), leaving only the low frequency power portion of the AC. Any extra resistance in the capacitor makes the ":shorting out" function less effective, and reducing the degree of filtering.

    If you use only the inductor in the filter, you get only at best half the filtering, and maybe less than that. Depending on the way the source of the noise behaves, the inductor alone may do almost nothing.

    I like the idea of the capacitors from the hot wires to neutral, but you can use one capacitor between the two hots. Using two, one from each hot to neutral, tends to remove both the "differential" noise and to some degree the "common mode" noise as well.

    Yes, generally the regular two terminal "motor run" type capacitors will be fine. One terminal to one hot wire, the other to either the opposite hot, or to neutral if you use two capacitors.

    One can also use electronic type capacitors, which work better for the higher frequencies. For across the line and line to neutral, those should be UL recognized parts rated as type "X" or type "Y", Normally using them will not be needed, the motor run types will be sufficient.

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    Quote Originally Posted by SND View Post
    I'm leaning toward 5% line reactors right now, supposed to be much better with harmonics than the 3%.
    I think I'll order a smaller 15hp model for the 10hp blue PP and see how it does on that, then get a bigger one for the 20hp PP if it really does what its supposed to.
    I've no idea about the whole adding capacitors to it though and how that would wire up. I'd have to see a picture of that to get the idea I think.

    I've seen really nothing about other off the shelf harmonic mitigation equipment. Seen a few mentions of digital systems to do it, beyond what a line reactor can do, but it appears to all be custom designed/built to fit specific applications, not something I can just order off a part #.
    A 15 hp 5% line reactor will have about a 6% voltage drop under load when the 10 hp Pp is running at full load. Electrically, a 15 hp 5% reactor will behave exactly the same as would a 10 hp 3% reactor in the same situation. -but the 10 hp inductor will saturate before the 15 hp does, the inductor is going to saturate anyways in the brief moment for DOL starting of a large motor. you would need a >40hp 3% reactor to avoid saturation when DOL starting a 10 hp motor. not practical.

    The reason for uprating the input reactor regarding hp, is because there is a 1.73 multiplier for the current drawn, as you probably know. but i don't want to suggest you buy a 500$ inductor when something much cheaper might be enough.

    Capacitors can be installed at the circuit breaker panel through another circuit breaker btw*.

    Adding some capacitors after the line reactor at the PP will take some of the ripple current off of the capacitors internal to the PP. connecting them line to line should be equally as good as line to neutral provided you don't have any common mode noise. note that the capacitive reactance goes with the square of the voltage. a 50uF capacitor across the 240v line is as much capacitance as is two 100 uf capacitors each connected line to neutral.

    *these capacitors are required. without them the inductor doesn't do much. But you might not even need the inductors if your PP is located far away from the house circuit breaker panel, in which case you can install the capacitors on your house's circuit breaker panel. (or at both)

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    I'm currently looking at some EMI Filters made to order, they list a few values for the capacitor they use and the leakage current that goes along with it. I'm not sure which to pick. Say for a 80amp 1ph 250v/60hz model. I can pick .47nf, 1nf, 2.2nf, 4.7nf, 10nf, 22nf, and 100nf. As the value goes up so does the leakage current. How do I know which is most likely to filter out the frequencies of the PP?


    One thing I did a few days ago was buy a bunch of clip on ferrites. I added 4 on each 1ph leg inside the blue 10hp PP. It seemed to make a fairly noticeable difference on that 10hp unit, and how little the microwave in the house picks it up anymore. I added 2 of the microwave cord as well. In the 20hp unit, it made no noticeable difference at the house panel, still buzzes, and the ferrites inside the 20hp PP are buzzing/vibrating a lot even just as idle. I wonder if thats good or bad now, definitely makes the pp sound different.
    They're vibrating a bit on the 1hp unit as well but not as bad.

    I mean, everything is still working fine without like it always has, maybe I'm worrying about this for no real reason but if it can be eliminated and no more buzzing in the house I'd sure feel a bit more at peace.
    I held off on ordering the line reactors for now, in part because of the space they'd take in the utility room and capacitors do seem to make more sense for solving this.

    thanks for all the input.

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    plug a 10uf or larger capacitor into the same outlet your microwave is plugged into. my guess is the noise will go away completely.

    Its hard to say what the clip on ferrites are doing for you, my guess is nothing. most clip on ferrite are intended for high frequency common mode noise reduction, and you install them as you did on your microwave: around both cables so there is no significant low frequency current through the ferrite.

    When you installed them inside the PP you are using them as inductors.. and they aren't intended as that. if you go back and add a very thin piece of paper between the halves of the core, then they won't saturate and they will actually behave as inductors. but they are expensive as inductors and that's why other core materials are used for that application. they will also have very little inductance.


    also it makes a big difference where you installed them in those units. presumably you installed them around the incoming supply lines before any other components correct?

    Coil32 - Multilayer coil calculator
    turns out you can get 100uH from 46 feet of 1 awg wire coiled around a 6 inch diameter spool, 2.5 to 3.5 inch wide coil, 4 layers, 24 turns of wire.

    this is probably enough of an inductor that two of them, one on each line feeding the phase perfect, combined with a 50uF capacitor at the breaker panel, forms an lc filter with a cut off of 1500hz that should stop 99% of the pwm frequency of the pp from getting through it. all that's left is common mode noise and there shouldn't be any.

    at 100 amps 60hz each of those 100uH inductors will drop 3.77 volts ac across them, which is about the same as the 3% line load reactor i suggested earlier.


    its probably better to just make 1, 200 uH inductor by winding both coils together, you only need 37 feet of wire for each coil. they have to be wound in opposite directions or the current cancels out.

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    So, I finally got around to adding a 40UF capacitor on each input line and other capacitor pole to ground, I used the original filter caps from when I changed them a few months ago, but cut the resistor off of them. Anyhow, it did eff all, still talks with the cooktop and microwave. A while back I put a couple other emi filters/surge capacitors on the breakers feeding them, that had again did eff all that could be noticed. I had removed the ferrite things after trying it a day or 2, just seemed to make noise in the unit in the end and nothing else. So, I guess its kinda back to a line reactor that would feed right through if I want to try anything else, might not bother as its all working anyway.

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    Quote Originally Posted by SND View Post
    So, I finally got around to adding a 40UF capacitor on each input line and other capacitor pole to ground, I used the original filter caps from when I changed them a few months ago, but cut the resistor off of them. Anyhow, it did eff all, still talks with the cooktop and microwave. A while back I put a couple other emi filters/surge capacitors on the breakers feeding them, that had again did eff all that could be noticed. I had removed the ferrite things after trying it a day or 2, just seemed to make noise in the unit in the end and nothing else. So, I guess its kinda back to a line reactor that would feed right through if I want to try anything else, might not bother as its all working anyway.
    Why did you remove the resistors?

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    Quote Originally Posted by Strostkovy View Post
    Why did you remove the resistors?
    Would not have mattered anyways.

    I am still curious if plugging a 10 to 50uf capacitor into the same outlet the microwave is on does anything.

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    I cut the resistors off yes.
    I haven't tried anything else with the microwave yet.
    IT's a bit weird that the old 10hp blue unit is the one that talks to the microwave, and the newer 20hp white unit is the one that talks to the cooktop.
    They do make different sounds so I guess different frequencies out of each of them.
    Hopefully they'll find a way to filter more of it out eventually, kinda looking at buying a 3rd PP and bring more power in here but we'll see.
    It mean it works and has for the 10yrs I've been running these and seems fine for everyone else as far as I know as well, but, I guess its just not all that reassuring since I've noticed a few things buzzing from the feedback it makes. I assume my neighbors are insulated enough from it since I'm on my own transformer at the pole, and they're on their own down the road, but I don't know how far that harmonic might spread.

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    SND

    I feel your pain. Just replaced 3 caps in my older blue unit. What a pain. Ended up taking it completely apart and still had to F with the wire harness. Crazy.

    Will be doing my 7 yr old PT330 next. Just as prevention. I have not experienced any issues as you have described ?!

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    Quote Originally Posted by SND View Post
    I cut the resistors off yes.
    I haven't tried anything else with the microwave yet.
    IT's a bit weird that the old 10hp blue unit is the one that talks to the microwave, and the newer 20hp white unit is the one that talks to the cooktop.
    They do make different sounds so I guess different frequencies out of each of them.
    Hopefully they'll find a way to filter more of it out eventually, kinda looking at buying a 3rd PP and bring more power in here but we'll see.
    It mean it works and has for the 10yrs I've been running these and seems fine for everyone else as far as I know as well, but, I guess its just not all that reassuring since I've noticed a few things buzzing from the feedback it makes. I assume my neighbors are insulated enough from it since I'm on my own transformer at the pole, and they're on their own down the road, but I don't know how far that harmonic might spread.
    Your pole or vault pig is a fair decent "LOW pass" filter, should attenuate the piss out of it before it bothers the local sharers of "the grid". but "otherwise"?

    Lemme tell yah. Schools for hard-of hearing kids need whole-classroom broadcasts and per-classroom separations. Hearing aids of the era all had "telephone coils" to pick-up off the then-still-prevalent magnetic reproducers in a handset.

    All we had to do was run a copper loop in the flooring a few feet in from the classroom walls. A decent-grade Audio amplifier "Dukane" PA system goods, IIRC - was then modified to run a 40 KHz to 100 KHz "carrier" onto which the teacher's microphone impressed telephone-grade audio bandwidth - roughly 300 Hz to 2700 Hz.

    And that class was "on the wire". Mebbe 20 X 30 feet or a bit less.

    Mid 1950's it was all the rage for those close to 50 KW "Clear Channel" AM or FM broadcast transmitters to power a still-novel transistor radio off rectification of the "free" RF, so some OTHER station could be listened to, no batteries or power cord needed, just a tuned circuit, low forward-drop Germanium diode and a decent capacitor.

    Radiant energy is one of those phenomena like "Slick Willie" Clinton.

    A "hound dog hard to keep on the porch" as Billary put it! It WILL just "get around!"


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    Quote Originally Posted by thermite View Post
    Your pole or vault pig is a fair decent "LOW pass" filter, should attenuate the piss out of it before it bothers the local sharers of "the grid". but "otherwise"?
    .....
    There's two kinds of interference.... "Common mode", and "differential mode". Common mode is when the "signal" is on both wires vs ground, differential is with it between the two wires.

    A transformer is pretty good for differential mode, although some can leak through. It is not very good for "common mode", the transformer acts like a capacitor, coupling signal right through to the high voltage.

    A lot of the noise from the PP or similar is going to be differential, which is attenuated and also tends not to broadcast very much.

    But some is common mode, which can travel through the transformer, and also can be broadcast from the wires more easily. This type tends to be a mix of frequencies, and originates from phenomena such as the slight timing mismatches between different IGBTs in the PP. While that sounds small, it can put out a pretty good signal.

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    Quote Originally Posted by JST View Post
    A transformer is pretty good for differential mode, although some can leak through. It is not very good for "common mode", the transformer acts like a capacitor, coupling signal right through to the high voltage.
    Not entirely. It also capacitance-couples a goodly ration of it to Earth. Lot more area there than in an ignorant run of wire or a mere audio transformer, hollow-state days. Not to mention that the high side isn't tuned to quite exactly encourage the dirty-deed, either.

    No need of high-risk snooping. An old multi-band six Dee-Cell portable on "Marine Longwave" band tracks it well-enough.

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    Quote Originally Posted by thermite View Post
    Not entirely. It also capacitance-couples a goodly ration of it to Earth. Lot more area there than in an ignorant run of wire or a mere audio transformer, hollow-state days. Not to mention that the high side isn't tuned to quite exactly encourage the dirty-deed, either.

    ......
    The windings are fairly close together in any transformer....to cut down parasitic inductance. Primary-Secondary capacitance is a given.

    There CAN be a shield.... bit there are several types.... most common is a wire winding placed between the P & S. That becomes less effective at high frequencies because it has inductance of its own, plus the lead wire. Better is a sheet of conductor (copper foil or aluminum foil) wound around 1 turn. That has minimal inductance plus lead wire, and is much better.

    Not all transformers have any shield, and the cheaper the transformer the less likely. "Pole pigs" (the supply transformer up on the pole) are the cheapest type, as they are installed by the millions. Probably some have shields, but as far as I know, most do not... most have been in place for decades.

    I know that the old Fenton MO Chrysler plant put noise on the HV lines that even 3 miles away was sufficient near the HV lines to blank out a clear channel 50 kW AM signal from a local station. A welding shop I know of did similar at least for a good mile away on the feeder line, the signal was blanked out by noise near the line, I am not talking noise plus the AM, it was all a loud roar, the AM was buried.

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    Quote Originally Posted by JST View Post
    I know that the old Fenton MO Chrysler plant put noise on the HV lines that even 3 miles away was sufficient near the HV lines to blank out a clear channel 50 kW AM signal from a local station.
    Hardly a small Phase-(Im)Perfect, though. is it?

    Tempting, here, for the OP to simply put a dirt-common EMI-RFI filtered "computer" power-strip or wall-outlet AC wart between Microwave and wall-outlet, same again that OTHER appliance, and see if it does the job. Cheap enough to try, and those gadgets have other uses as well. Media system, etc.

    I'm getting mobile "enough" again, coming off injuries, to hope to have 'scope traces before the end of the month.

    I don't expect to have to do anything more than what the stock Square-D loadcenter add-in or add-on filters cover.

    Even though they are not specifically matched to the issue here, nor even all that close to highly effective attenuation, they should be more than good enough to "save the kitchen". And the puters, hubs, routers, security or motion-sensor lighting, and similar 'tronics most present-day residences are full of.

    If not? THEN I'll see what else is out there, "rated" and to-code, but not DIY. It just isn't a wheel as needs a lot of new "invention". It is cheaper and easy to just try stock solutions, measure the results, then move on to some tougher challenge as and when "good enough" day arrives.

    I actually would expect more issues, HERE, my own place, than the Phase-Perfects "now and then" contribute to arise from my lower-powered DC-ification goods.

    The 10EE's with SSD's needed boost in any case for single-phase DC Drives, and got full isolation into the deal. "Clean enough" as they are now.

    All the rest are 180 VDC motors off far simpler - and noisier - KB-Penta Drives where I had NOT planned Drive Isolation Transformers. Only fat CORCOMS, mostly KB-branded.

    More when I have more as to what "only the Rigol knows!".


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    Quote Originally Posted by thermite View Post
    Hardly a small Phase-(Im)Perfect, though. is it?

    T.....
    The welding company is a closer match...

    Both had appreciable leakage of noise right into the power line, though. Shows it can get through transformers of widely different sizes, and in amounts th obviously be an issue for FCC limits and annoyance to neighbors. And the welding company would be a close match as inverter welders and PP both use very similar technology.

    The plant would have been chock full of VFDs, all pretty much the same tech as a PP..

    All these things are very situation-dependent. It is very difficult to say if a specific case will have a problem. But any bower switching deviice with OGBTs or the like can clearly cause a problem.

    I'd install it, and then check with a radio to see if there are issues. May be, May not be. I understand the newer PP are much better as far as filtering than the old ones.

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    Quote Originally Posted by JST View Post
    I'd install it, and then check with a radio to see if there are issues.
    He has done arredy. EMI exists.

    This forum should come with Veeder-Root turns counters. So we know how many laps were have repeated, same karusell, same pony, theory, or armchair.

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    Quote Originally Posted by thermite View Post
    He has done arredy. EMI exists.

    This forum should come with Veeder-Root turns counters. So we know how many laps were have repeated, same karusell, same pony, theory, or armchair.
    HE has issues, although they seem to be mostly a buzzing in the panel....but if we are talking about the supply transformers, it sounds like the neighbors may be getting them also? I do not recall seeing that...

    The comment was more about any others thinking about installing something that might make for interference off the property. You don't know until you try it, because there are so many unknowns in the power system that any attempt at an analysis will take longer than a straight up try-out. If it makes interderence, put on a filter, and if it does not, you are good.

    I thought he was going to put emi filters on the microwave and cooker, since those are the things that seem to be a problem. Then see if there are other issues elsewhere, But I believe IIRC, and if this is the correct thread, capacitors did not solve the problem....

    A filter to put on the PP itself will be expensive, but, looking (Digikey) at ones that would handle a cooktop (30+ A at 240VAC) those are not common and are expensive also, so it might be better to look at the source.... the PP.

    This may just not be that important.....

    If there is any further interest in dealing with it....

    There is a chance that the noises are not actually due to typical EMI, but to lower frequency disturbances that make the noises more by vibration than by some exotic interference (although there are always sum and difference frequencies,,, that could be it also). Putting a capacitor on the line should have knocked out much of the high frequency stuff, should have changed the noise, even if the capacitor was not very good at high frequencies.

    The PP are supposed to have a Power Factor correction scheme that presumably cuts out line harmonics, but it may also have interactions with other equipment.

    What sort of "buzzing" is it causing? I do not think we have that info. There are all sorts of "buzzes" and they can mean different things, depending on what sort they are.

    Also, does it make those two items buzz even when they are not cooking and so are not drawing much power? That would be a lot different vs buzzing when they are "on" and cooking.

    I do not recall if the PP caused that when at idle, or when supplying power to machines. Was that stated?

    Actually, the whole thread portion about this buzzing and apparent interaction of the devices is fairly worthless without some scope photos, and/or a spectrum analyzer trace of the power line from the PP and at the other devices. That sort of thing is "data", and what we have is not enough "data" to really understand what is going on in his case.

    It is not at all clear that the actual problem is what it appears on the surface to be. Might be, of course, but might be something a bit different. I admit to being very curious as to just what it really is, but I do not suppose we will find out.
    Last edited by JST; 12-07-2018 at 01:58 AM.


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