haha, ok fair enough I thought we were talking HF switching noise for a moment.
you know the stuff that looks like un-triggered grunge or 'glare on an analog waveform trace.
Agree with this answer.
Even if the inverter's o/p is grounded, you can still find out the live and neutral, and just match your scope's ground lead with inverter's ground.
I did this several times on welding machines. If you confuse wires, fuse in the inverter will blow up.
Not sure how PF got inserted into the discussion, but it certainly has nothing to do with the flat topping of a sine wave. Post #25 I believe - we are definitely not talking about the same thing.
Power factor and crest factor are not the same. I can hook up a large induction motor to house power, and it will produce a very poor (say 75%) lagging power factor. The current drawn by this motor will be extremely sinusoidal, and will NOT produce the flat topping of the sine wave as shown earlier. It may sag the voltage, from 120V down to 110V, but the overall distortion of the voltage will be very clean.
I can hook up a large capacitor bank to house power, and will produce a leading power factor. Same conditions, though - sine wave current produces no distortion in voltage.
Rectifiers, on the other hand, are nonlinear loads and will produce harmonics and result in a high crest factor current (peaked) waveform. This peaking is what produces the voltage distortion. A rectifier-capacitor input power supply actually provides a fairly good power factor, near to 100%. Drives, for example, provide a slightly leading power factor, owing to their capacitor storage.
Distortion seen is not the result of good/bad power factor; it is the result of harmonics generated by nonlinear loads.
Power factor and crest factor are not the same. I can hook up a large induction motor to house power, and it will produce a very poor (say 75%) lagging power factor. The current drawn by this motor will be extremely sinusoidal, and will NOT produce the flat topping of the sine wave as shown earlier. It may sag the voltage, from 120V down to 110V, but the overall distortion of the voltage will be very clean.
I can hook up a large capacitor bank to house power, and will produce a leading power factor. Same conditions, though - sine wave current produces no distortion in voltage.
Rectifiers, on the other hand, are nonlinear loads and will produce harmonics and result in a high crest factor current (peaked) waveform. This peaking is what produces the voltage distortion. A rectifier-capacitor input power supply actually provides a fairly good power factor, near to 100%. Drives, for example, provide a slightly leading power factor, owing to their capacitor storage.
Distortion seen is not the result of good/bad power factor; it is the result of harmonics generated by nonlinear loads.
poor loads and IR drops NOT the transformers being driven near saturation was the thrust of my response > my earlier post gave an example of a poor load being a capacitive input charging power supplies as found in many older SMPS (no PF converter input stage) they do indeed have a narrow conduction angle (resulting in poor PF) and they are well known to be poor loads since all the high peak current used to produce the RMS power is confined near the voltage peaks. obviously there's a discontinuity in the waveforms due to rectifiers and the capacitor sagging voltage. BTW Distortion is figured mathematically from the discontinuity not the diode circuitry or topology. add all the verbiage you want the idea was expressed correctly before yours. BTW thanks for not acknowledging anything I said before you in essence repeated it. echo, get it now?
PS don't bother arguing chicken /egg aspect of PF with me its a poor load regardless. the PF angle is between the two zero crossings and is not good at normal loads or else why would they bother correcting it modern SMPS designs.
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This is true, and I fully understand the difference.
The SMPS industry, specifically those marketed for diy PC's, either does not know, or does not care, since they tend to use the term "power factor" to describe a power supply's ability to meet the EU's requirement to draw current for all, or most of the input sine wave's cycle, regardless of the actual phase angle of that current. There are efficiency requirements to meet though.
Older power supplies simply rectified and bulk filtered the incoming AC and fed it to the SMPS converter. The newer PFC (Power Factor Correction) supplies use a modulated boost converter to step the incoming AC up to about 400 volts DC. The apparent step up ratio changes over the incoming AC cycle such that current is drawn over nearly the entire cycle.
Nope. They still exhibit good power factor. My point that you don't hear. Calling an input stage power factor corrected is actually a misnomer. These stages correct for harmonics by forcing the current to be drawn as a sine wave (as Tubelab correctly pointed out). Power factors can actually be very similar between a corrected and non-corrected input.
Point being, power factor is irrelevant in this discussion, but you claimed it's the root cause.
Nope. Power factor is the cosine of the angle between the fundamentals. I don't care for the propagation of false engineering statements, which is not uncommon in audio circles. One could also discuss a recent addition: "true power factor", which takes in account the effect of harmonics. They are definitely not interchangeable, nor does your utility charge for true power factor (at this time). Some industrials get charged for power factor, but not true power factor.
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yes I hear you repeating the same things i said. The main point I am trying to convey here is the that transformer isn't saturating under loading.
conduction angle is what i should of said instead of PF, BFD.. also PF correction is the SMPS industry term for the boost converter on the front end of a SMPS whatever, some ppl jeeze
conduction angle is what i should of said instead of PF, BFD.. also PF correction is the SMPS industry term for the boost converter on the front end of a SMPS whatever, some ppl jeeze
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Let's see. You said:
I reply:
You also said:
I reply:
Sorry, but we are worlds apart, and I don't think you fully understand the jargon you throw around. I'm not repeating what you say, I'm correcting it. Sorry if that's inconvenient for your ego.
I understand the point about how the core of a transformer can be saturated. We chase that demon a lot in tube amp design using "repurposed' transformers for OPT's.
Rather than continue to discuss this in a thread not related to transformer saturation, let me restate what I said earlier.
About a dozen years ago they swapped out the transformer in our neighborhood. At that time other anomalies began to appear such as buzzing a power transformer in a tube amp that had not buzzed before. This prompted me to investigate the quality of my AC power.
I took measurements and scope pictures of my power at several times during the day over several weeks and had several arguments with FPL over the phone. They no longer guarantee and distortion specs for residential customers. Industrial users like the Motorola plant where I worked went from 3% to 5% in the 1990's.
Some of the pictures revealed a waveform that LOOKED like transformer saturation. The same waveform is observed in a tube amp when you lower the input frequency until the output tube current increases dramatically. I could even be wrong about that, it was 10 to 15 years ago.
I don't care to speculate or argue if the issue was or was not pole transformer saturation. I don't even remember if that particular waveform was at peak loading times, or if it occurred during times of high line voltage. I don't have the photos available currently, but they may still be on one of the archived hard drives I have stashed from that time period.
Yes, standards have largely absolved utilities of having to provide distortion targets. For example, WI Public Service Commission 113.0704 (I am formerly from there - which is designed to protect the consumer) states:
"Utilities shall make reasonable efforts to investigate equipment operating problems suspected to be associated with harmonic distortion of the 60 Hz voltage sinewave at the point of service. When the source of the harmonic distortion is determined to be equipment operated by a specific customer, the utility shall notify the customer and it shall be the customer’s responsibility to correct the problem. When corrective action is necessary, the guideline to be used is the 1992 IEEE Standard 519"
IEEE 519 sets out minimum standards for individual or group harmonics, specific to current harmonics which ultimately affect voltage distortion (based on per unit impedances of transformer and source) . In your case, you might have had a flat-topped sinewave and linear loads, but aside of installing an inverter-based FACTS system nearby (not gonna happen) their only recourse would be to put the screws to local violators. This does make some sense, since the utility is not the harmonic generator, users are.
"Utilities shall make reasonable efforts to investigate equipment operating problems suspected to be associated with harmonic distortion of the 60 Hz voltage sinewave at the point of service. When the source of the harmonic distortion is determined to be equipment operated by a specific customer, the utility shall notify the customer and it shall be the customer’s responsibility to correct the problem. When corrective action is necessary, the guideline to be used is the 1992 IEEE Standard 519"
IEEE 519 sets out minimum standards for individual or group harmonics, specific to current harmonics which ultimately affect voltage distortion (based on per unit impedances of transformer and source) . In your case, you might have had a flat-topped sinewave and linear loads, but aside of installing an inverter-based FACTS system nearby (not gonna happen) their only recourse would be to put the screws to local violators. This does make some sense, since the utility is not the harmonic generator, users are.
well I'm not sorry if the power supply industries terminology doesn't fit your world view. Sometimes industry conventions are useful for engineers to communicate to each other about a particular concept in a shortened manner. as an example google "PF correction + power supply" take a good look around. I wish you good luck on your latest silly crusade. It's not productive to derail a thread to nit pick details that just don't matter, but that's your problem not mine. Don't you remember your last miserable crusade failed too > trying to inform DIYA members to bond their safety testing isolation transformers secondary to PE ground. yeah yer right sometime electricians and electronics practices don't mix well.
understood it's a common mistake even for the magnetics experienced, It took me a while to get volt*seconds drilled down as a concept even after my 2nd or 3rd transformer build was under my belt.
voltage and time (1/freq) are the two big things that power companies tightly control.
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A well designed PSU should isolate mains perturbations from the amplifier.
You should not hear any mains effects in the amplifier.
Dirty AC input to a clean DC output. That's your target.
Agreed, and you won't hear any ELECTRICAL effects in my amps. I test them by plugging a 20 year old electric drill with dirty worn brushes into the same electrical outlet as the amp.....try that with some amps.
However, there is nothing you can do, short of regenerating a perfect sine wave (and that doesn't always work) that will stop some power transformers, particularly the 200 series Hammonds, from MECHANICALLY buzzing.
The amp in question uses an Allied Electronics transformer, which is a rebranded Hammond.
Hi Andrew I visited your thread and it wasn't clear what youre testing for.
if youre making measurements on DUT / circuits on the primary side then my earlier posts in this thread will apply E.g use an iso. XFMR floating the DUT. If not working on the primary side per se and your isolating from noise and such, a dedicated mains run to the panel is often better (stiffer ) than using just a transformer. If youre worried about the DUT injecting noise into the mains, other techniques and mains filtering will be needed. Ultimate noise RF rejection at the DUT will require a combination of things> see stajo's thread again, the figure I posted at the bottom.
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Agreed, within reason.
Agreed, within reason. I've seen some really bad power in my days, but surprisingly many pieces of ordinary gear were able to continue playing well, despite it.
The worst power I ever saw was due to a remote area in Germany receiving power from two power plants that were out of synch. This resulted in power line voltage cycling every 2 seconds or so. The voltage variation was such that incandescent light flashed almost like strobes. Fluorescent light phosphor had a long enough persistance to compensate. Some gear survived, some gear failed.
On the "failed" list was a 200 KW 50 Hz-> 400 Hz static inverter. While this was all going on, you could just about see it twisting on its concrete foundation, with sounds to match.
That is generally the goal of the engineer who designed the power supply in the gear. Designing really clean power supplies got to be a whole lot easier with the advent of low cost IC regulators about 40 years ago.
If people were obliged to use bias-controlled listening tests to indict the power supplies of audio gear, much folklore probably would have never happened.
If I am using my lab power supply to power up an experiment/project then I am relying on the isolation provided by the sealed up lab supply.
I see no problem with that arrangement.
I will need to go and check, but I am pretty sure the socket outlets under my bench are supplied via a 25A 30mA RCBO in my distribution board fusebox. There are six RCBO in there for all my power rings around the house. Dedicated power to water heater, hob, central heating and 3phase tools, only have MCBs
If I am powering up a project with mains power into a "normal" mains transformer, I have Live & Neutral on the bench.
That could lead to mistakes and/or injury.
It is for this that I would like something safer, so that if a mistake were made I survive and preferably the project survives. MCB/s and RCD/RCBO on the isolating transformer may be required.
A "nice to have" feature would be the ability to connect the scope probe ground lead to any part of a mains powered project and be able to measure the voltage across a component. I think an isolated supply would allow this, but I may be wrong.
Interference attenuation is a different issue.
Any attenuation would be secondary and after the safety side is sorted.
I could use screened/shielded mains cable into and out of the isolating transformer. I could use a PE connected enclosure around that transformer. I could add on a mains filter, either the canned type, or I have components to add on a second more elaborate if required.
Here is my take on the subject:
http://www.diyaudio.com/forums/equi...be-direct-mains-measurements.html#post4575143
http://www.diyaudio.com/forums/equi...be-direct-mains-measurements.html#post4575143
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