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  1. #21
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    If you can stand a used unit, look for a Fluke 41B.

    It is a single line power harmonics meter, and will probably do anything you need. I have seen them on ebay with all the goodies for as little as $300 or so. I have used one, and would buy another.

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    Quote Originally Posted by JST View Post
    If you can stand a used unit, look for a Fluke 41B.

    It is a single line power harmonics meter, and will probably do anything you need. I have seen them on ebay with all the goodies for as little as $300 or so. I have used one, and would buy another.
    I agree with JST. I think this will give you the most bang for the buck.

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    Unless you really want to get into electronics analysis I have to recommend either renting the proper equipment or hiring someone to do it for you.

    I hate the “just buy something better or get somebody to do it answers”, so I hate giving one, but by the time you buy the scope, probes and invest the time in learning how to use it all in a useful manner you’re looking at an investment you’ll feel in your wallet. That’s assuming you’ll have everything you need to actually do anything with the information you collect.

    You can get lost in electronics and it’s not hard to spend the same amount of money on the equipment as you do on your shop tooling.

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    Or, other option is to simply contact the company (phase perfect) as they no doubt have *done* the measurements themselves
    as a normal part of marketing and selling an item like this, and will be pleased to provide the information regarding their harmonic
    content backfeeding into their supply lines.

    Sure.

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    Quote Originally Posted by jim rozen View Post
    Or, other option is to simply contact the company (phase perfect) as they no doubt have *done* the measurements themselves
    as a normal part of marketing and selling an item like this, and will be pleased to provide the information regarding their harmonic
    content backfeeding into their supply lines.

    Sure.
    I really haven't gotten much out of that other than it can and does happen. If you want to try on your end and see what you can find beyond the basic specs on their site that state pretty much nothing about this, please let us know.

    Though that also might not really help much when a unit has been running for a few years, stuff starts to age, filter caps life appears to be all over the map from some going 10yrs with no issues to some being cooked within a few months. So figuring out a better means to check this out and monitor it regularly before big problems happen or something catches fire would be kinda nice.

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    Quote Originally Posted by SND View Post
    ...try on your end and see what you can find beyond the basic specs on their site that state pretty much nothing about this, please let us know.
    ....
    Possibly you may have figured that I was being ironic. From what I have heard about phase perfect, they work great when they are working great. But if anything goes
    wrong, the unit is 'no longer supported' and if you want any information from them about what's inside or things like "how much RFI hash *does* it put back into the
    line, then the owner is basically SOL.

    Some more modern scopes to have built in fourier transform software so that would be the best place to start if you cannot get a real honest to goodness power line
    analzyer.

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    If you need NUMBERS, it's one thing. If you just need to lnow basically if it is a lot or a little, which means "can I see it on a scope when the scale is set to have the whole ave on the screen", then a scope woud be OK, and you can zoon in with any digital scope to see what frequency it is, etc. With most you can set two crosshairs and get the time between them which will give you frequency if you select beginning and end of one "cycle" as the crosshair locations.

    With the PP, the frequency may be higher than the common 25 harmonic range of power quality meters, since that only reaches to 1500 Hz. (It is fine for actual harmonics of 60 Hz, just not universal enough for "interference"). I am told the PP frequency is 5 kHz, that was given in another thread..

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    I've got a pretty good 4 channel siglent 100mhz oscilloscope on the way and a 200-2000x differential probe for extra safety.
    Should work pretty good to see what's going on, and what effect adding anything else to the circuit will do.
    Still thinking of adding a line reactor to the PT355 and also looking forward to putting 480v filter caps in it once those become available.
    I'm hoping with regular monitoring it might help me figure when caps or any other components are starting to go, and perhaps when a PP unit is near the end of its life.

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    Quote Originally Posted by 9100 View Post
    I use a Tektronics 453 that is considered ancient but it works as well now as it did when new. I do have to be careful about grounds. You don't need a super wideband scope for 60 cycle work. The harmonics are mostly multiples of 60 and most are well within the range of almost any scope. I have used the 453 in the last few days, first looking at RS232 spurious signals and then on the waveform of a saturable reactor used to limit current in a mag base drill.

    There are countless oscilloscopes, both CRT and handheld on EBAY at low prices.

    Bill
    That's a great scope, with its nice sharp display! I prefer mine to my faster 475.

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    SND, I think I understand what you are trying to do, which is proactive testing of a PP so you can catch issues beforehand. There is probably a much deeper discussion here in what you are 'really' testing, and the best methods to test it. As an example, if I am looking for bad caps in a DC rectified circuit, I do NOT test for capacitance, I probably will be testing mVAC or ripple, in which I have a high end Fluke DMM that stupid accurate.

    In a nutshell, a digital scope with battery pack option WILL do about anything you need, BUT you have to actually understand what you are testing, the probes, etc, etc. Consider that I can either give you an engine or a CNC machine. The CNC can make the engine, and many other variants, but not the other way around. But, you will have to actually learn how to run the CNC machine. Fluke takes some of the functions away and adds focus on the areas you really need in a certain field. It has immensely pissed me off to have Fluke clamp meters that don't read high range resistance. They read OL! It has fucked me out hours of time only to grab a cheap DMM and see the actual value. Quick story.....had a limit switch acting up. Used a Fluke clamp and it showed like .1ohms when closed, and ""OL"" when open......YAY! However, that little bitch was actually like 2-5kohms when open (or whatever it was)...... Had I seen that, it would have changed the game.

    Anywho, if you want the ultimate tool and want to learn and build, get a good 2-4ch digital scope. If not, the Fluke above will give you decent functions. I will admit, sometimes I like the simplicity when I know what values I need.

    THD can EASILY be both seen and calculated on a scope. However, I suspect you won't even need the actual value because once you know what a sine wave looks like, you will EASILY see issues with the wave form. For a real EE, hell, they can damn near spot the issue just looking at the wave.....Which is EXACTLY why I prefer scopes.

    A scope will probably need amp clamps for best use, which are just inductive hoops, same as a clamp on a clamp meter. Once you can see both the current and voltage wave forms, you have some very good data for review, which is how watts, real power, apparent power, PF, etc, are calculated.

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    Quote Originally Posted by huleo View Post
    ... sometimes I like the simplicity when I know what values I need.

    THD can EASILY be both seen and calculated on a scope. However, I suspect you won't even need the actual value because once you know what a sine wave looks like, you will EASILY see issues with the wave form. For a real EE, hell, they can damn near spot the issue just looking at the wave.....Which is EXACTLY why I prefer scopes.
    THIS.

    One only needs "ALL the numbers and ALL the math" in the environment of R&D, design, and test of NEW goods.

    Otherwise, detecting a(ny) of the many symptoms of a given problem is good enough to send-off for new parts, upgraded parts, or add-in filtering.

    Mostly, we have other priorities as to JF using a P-P and "now and then" casting a watchful eye on its general health [1] rather than re-inventing the SOB.

    Bill

    [1] An AM radio can do that part... cheaper the better

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    The issue I see here is that performance is based on the capacitors. I am not familiar with PP's, I haven't seen a diagram or description of how they work.

    SND you want to spend money of test and monitoring equipment. Why not put that money to a better use and replace the capacitors with oil filled? Yes they are expensive, and yes they are bulky, but this should to bed forever your concern about the PP malfunctioning, excepting of course the electronics. Might take an extra box, nothing more serious.

    Tom

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    it seems likely that the approvals, etc are based on the capacitors actually used. Granted that the PP folks seem to beat the heck out of them in the application, as evidenced by the fairly short life, the chosen parts also may have the properties needed for effective suppression of the noise. Substituting other types may not provide the same suppression, may even have SHORTER lifetime, and so may not fix the problems the original type fixes.

    My suspicion is that PP would not put up with the lifetime problems of the existing capacitors if they had a better choice. It is pure guesswork trying to put in a "better" part when you cannot be sure what the original designers needed that the original parts supply. They have access to any part wanted, and they chose what they chose. I can see a substitution not ending as well as intended.

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    Educate me. What the motor run caps used in PP's, paper, electrolytic, or what? If electrolytic are they two dc caps back to back? What is the failure mode? What causes the failure? Of course we know here that heat can be from ambient conditions and from Internal generation. We also know that chemical reactions double in 10C rates. Is the failure from chemical deterioration of the dielectric compound?

    My experience is that oil filled caps are better on ac.

    Tom

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    Quote Originally Posted by TDegenhart View Post
    Educate me. What the motor run caps used in PP's, paper, electrolytic, or what? If electrolytic are they two dc caps back to back? What is the failure mode? What causes the failure? Of course we know here that heat can be from ambient conditions and from Internal generation. We also know that chemical reactions double in 10C rates. Is the failure from chemical deterioration of the dielectric compound?

    My experience is that oil filled caps are better on ac.

    Tom
    Much the same goods as used in VFD. They have both working deterioration lives and age-even-if-unused chemical life limits.

    "White case" P-P model manual recommends replacement at 3 years, whereas most VFD are 5, 7, 9, even 12 year recommended intervals (longer than most stay in service, industrially, on average..), and some of the "grand old" VFD have run 20+ years, just as even blue-case P-P have run 10, 15 or so.

    Oil-filled? yah but.. In the voltage & MFD needed they could be stock Utility company goods, but each ONE about the size of the whole P-P and costly as all Hell.

    Cheaper to just do the recommended replacement by the calendar ..

    ..and/or "maybe"... add the classical small-value solid-tantalum plus smaller-yet silver-mica paralleled for bypassing fast-rise artifacts?

    One still has the chemical degradation age-limit, so not sure if it is of actual value vs JF run it as-built and swap on-schedule

  20. #36
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    Quote Originally Posted by TDegenhart View Post
    Educate me. What the motor run caps used in PP's, paper, electrolytic, or what? If electrolytic are they two dc caps back to back? What is the failure mode? What causes the failure? Of course we know here that heat can be from ambient conditions and from Internal generation. We also know that chemical reactions double in 10C rates. Is the failure from chemical deterioration of the dielectric compound?

    My experience is that oil filled caps are better on ac.

    Tom
    Electrolytic are not used for AC application, although there may be another set of DC bus capacitors which are in fact electrolytic.

    The parts I have seen pictured and stated to be the problem ones have been metal cased motor run or PF correction types (very similar).

    The metal cased parts are in every instance I have seen, basically paper and foil parts (two pieces of foil, with two pieces of paper to keep them apart when rolled up) , usually "oil soaked", as opposed to oil "filled"... there is generally no oil sloshing around in there. They have a fuse element, which can go bad, in which instance they are suddenly "open", no capacitance. The oil improves the dielectric properties of the paper.

    There are also film types, which may be either foil and film, or metallized film, with a thinnish coating of metal on the film. These can be either in a plastic case, or the typical metal run-capacitor type case.

    Foil and film are heavy duty, and just use plastic film in place of the paper and oil. The foil can carry heavy currents, the limit it s the allowable film temperature. With 4 layers, they are bigger, but may be slightly smaller than paper and foil.

    Metallized folm tend to be "self-healing", if a short develops, the metallization is blown away in that area, and the fault is "healed" (rather drastically, but effectively). That does lower capacitance, so after a number of faults, the capacitor may not meet the spec it is labeled as. These have just two layers of film, plus thin metallization, and are smaller. If metallization is thicker, the part is for heavier current, and also will likely not "self-heal".

    The metallized film type has an actual "wear out" mechanism that is somewhat gradual as areas of the metal are disconnected by the faults blowing connections. The others tend to either work or fail, although it is possible for a fault to not kill them, if the foil is cleanly blown away by the arc.... unlikely but possible,

    Failures are heat related, degrading insulation, and can also be from spikes causing internal arcs, or from defects that were not quite bad enough to fail the testing, but fail later..

    Here is a metallized film run capacitor that failed catastrophically. It internally shorted or arced, and melted the metallized film into a glob. Connections were made to the metallization by welding strips to "end metallization", metal sputtered onto the ends in such a way that it contacted the metal coating on the film, each alternate layer (one of the two strips) at one of the ends. It opened the circuit internally due to the high current.

    You can see the metallization of one layer extends past that of the other.... that is how one strip is contacted by the metal sputtered onto the end. The "goo" you see is a soft wax material used to hold the innards in place inside the case.




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    One low budget process is simple wall warts.

    Transformer will both isolate voltages and reduce to low voltage.

    Some noise may be lost but actual signals present should pass the transformer.

    One must use either a pure passive unit that only contains a transformer or locate a dc one and remove the diodes.

    Best to find 3 identical units to create a delta connection on input.

    Be careful and safe.

    Sent from my SAMSUNG-SM-G930A using Tapatalk

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    PP is working on upgrading to 480V caps. The PT-380 and up units now use them as far as I understand and it sounds like the other units will switch to it at well soon, they're different uF for the 10hp and 20hp models.
    I'll upgrade to 480v's as soon as they're available.

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    Quote Originally Posted by Archer120x View Post
    You really need current probes to get a good sense of what is going on.
    Are there useful DIY current probes for automotive work?
    I would like to be able to evaluate solenoid operation with my TEK 465

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    Quote Originally Posted by n2zon View Post
    That's a great scope, with its nice sharp display! I prefer mine to my faster 475.
    My Tektronix 453 which I have had since it was new failed from what I understand is a common problem with these and similar Tek scopes. The HV transformer epoxy insulation becomes conductive over time. Initially you may notice that the trace disappears after being on for an hour or so. Eventually no trace even when cold. One or two guys over on TekScopes (groups.io) have successfully rewound theirs, but otherwise there appears to be no hope. Sad, this was always my favorite scope. If you find 453s on ebay or elsewhere, be aware that most if not all of these will eventually have this problem.


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