Sniff...
WHats that smell...
Urine!
Ive jumped into yet another DIY ****ing match.
I'm outa here before my otes get wet.
Ciao!
http://millinfo.org/upsfire/
WHats that smell...
Urine!
Ive jumped into yet another DIY ****ing match.
I'm outa here before my otes get wet.
Ciao!
http://millinfo.org/upsfire/
The issue here Fred, as Martin alludes to, is the step-up transformer raises o/p Z.
Add a highly non-linear load (rectified DC supply) and all the low distortion performance in the oscillator goes out the window, as bad, if not worse, as the conventional mains.
You can add feedback at LF around the transformer, but can't really extend this beyond very low frequency, due to the phase shifts.
Did you measure THD at the o/p under a real world load?
BTW, those that think the incoming mains is a nice 50Hz (or 60Hz) sine, think again
Here's mine at various times of day, it peaks around 5-6% THD at busy times, drops to 1/2 to 1/3 this late at night, with mainly the high-order harmonics falling...
Attachments
Well, it's an option, but the cure can then becomes more of a problem than the disease.
The problem here is that the mains distortion comes primarily from the non-linear loads connected. Most LPF's I've tried raise mains Z to much, and this is actually more audible than the distortion already present and whilst isolating the equipment from the mains distortion, it then increases it within the device, due to the small conduction angle of rectified mains supplies.
Some attention to power factor correction is the order of the day, I feel.
Interestingly the power plant devices have the option of more distorted, non-sinusoidal ouptuts, which are reported to sound better - I wonder if it's some simple attempt at pre-distirtion, in an attempt to improve the result under load?
Andy.
ALW said:
I wouldn't exclude that at all. The shape and the harmonics come from the way the alternator is designed, the shape of the sin output is a direct result of how the "lobes" (for lack of a better english word) of rotor and stator. I think the only thing they care about is efficiency, there are some minimum output shape requirement but the rest is pretty much done in function of efficiency. That is efficiency at steady state and nominal load, which is the only way generators operate.
Harmonics add nothing to efficiency, they actually add to the useless power that needs to be dissipated in the step up and down transformers and as such an attempt is made to minimize them as much as possible during generation.
As stated before, a large portion of harmonics are generated by the load.
In some parts of europe power users above a certain number of kW are required to rephase their inductive or capacitive loads so as to "look" resistive from the standpoint of the supply that helps ,I think.
power factor + harmonics
hi
power factor is very important for the energy suppliers. They issue stricter regulations, i think a new euro norm is out now. this requires devices with more than 75W power consumption to conform to some regulations, which, at least in the case of SMPS, are easiest to achieve with a PFC pre-regulator (a boost converter..).
So, most consumer devices, like PCs, TVs etc will fall into this category and modern devices already have PFC. a way to identify them; if the device is capable of running with "any" mains from 85 to 265 V or so, it has a boost converter that steps the voltage up to say 400V and the SMPS run off that.
A bit hard to use for the average amateur. To take advantage of it a SMPS is needed.
well of course a PFC boost converter can be run off of the secondary of a transformer... then you get lower voltage that is directly useful for an amplifier. But only bad regulation (at least some..).
Also, you'll need to take care of the noise that the PFC circuit generates.
Re: harmonics:
in motor drive power converters it is an easy way to get higher efficiency if you add third harmonic to the "target wave", then the output is closer to a rectangular wave which is easy to achieve.
Maybe the power generation guys do it the same way. The third harmonic is useful - why would it be dissipated in the lines? And the distribution transformers probably have enough bandwidth to transfer it... it's just 150 Hz.
regards!
keyne
hi
power factor is very important for the energy suppliers. They issue stricter regulations, i think a new euro norm is out now. this requires devices with more than 75W power consumption to conform to some regulations, which, at least in the case of SMPS, are easiest to achieve with a PFC pre-regulator (a boost converter..).
So, most consumer devices, like PCs, TVs etc will fall into this category and modern devices already have PFC. a way to identify them; if the device is capable of running with "any" mains from 85 to 265 V or so, it has a boost converter that steps the voltage up to say 400V and the SMPS run off that.
A bit hard to use for the average amateur. To take advantage of it a SMPS is needed.
well of course a PFC boost converter can be run off of the secondary of a transformer... then you get lower voltage that is directly useful for an amplifier. But only bad regulation (at least some..).
Also, you'll need to take care of the noise that the PFC circuit generates.
Re: harmonics:
in motor drive power converters it is an easy way to get higher efficiency if you add third harmonic to the "target wave", then the output is closer to a rectangular wave which is easy to achieve.
Maybe the power generation guys do it the same way. The third harmonic is useful - why would it be dissipated in the lines? And the distribution transformers probably have enough bandwidth to transfer it... it's just 150 Hz.
regards!
keyne
Re: power factor + harmonics
I am not talking about inverter driven AC motors but about generated power at the station.
What I am saying is that the fundamental is 50 or 60Hz, the lineshape is whatever it comes out to be. The goal is highest efficiency.
Harmonics are generated no matter what it's just not very good to have them. Try putting a rectangular wave through a transformer see what comes out, the difference is all dissipated power. When you think in terms of megawatts a mere 0.01% is alot of power.
keyne said:
I am not talking about inverter driven AC motors but about generated power at the station.
What I am saying is that the fundamental is 50 or 60Hz, the lineshape is whatever it comes out to be. The goal is highest efficiency.
Harmonics are generated no matter what it's just not very good to have them. Try putting a rectangular wave through a transformer see what comes out, the difference is all dissipated power. When you think in terms of megawatts a mere 0.01% is alot of power.
Correction on power factor correction
This is becoming a fulltime job.....
http://www.pioneermag.com/power/application.html
This is becoming a fulltime job.....
http://www.pioneermag.com/power/application.html
Re: Correction on power factor correction
Who are you correcting?
It took you two days to pull this obscure reference that is marginally related to the discussion at hand w/o explaining the relevance of the link.
I am writing a JACS communication but I guess I can just go play in the pool since all I need is a snotty title and a list of references.
Fred Dieckmann said:
Who are you correcting?
It took you two days to pull this obscure reference that is marginally related to the discussion at hand w/o explaining the relevance of the link.
I am writing a JACS communication but I guess I can just go play in the pool since all I need is a snotty title and a list of references.
I have at least 200 different ups units at work. Best ferrups,
best fortress of various sizes, apc's of various sizes...
Best ferrups. Completely on line unit which consists mainly
of a ferroressonant transformer. It takes over for the few
milliseconds it takes to switch to battery power. Output is
a clipped sine wave under ALL conditions. In addition when
used on loads with nasty power factors, the distortion can
easily exceed 20%. Bundles of thd.
Best fortress are all off line units. When in ac mode everything
does go thru the transformer which does a great job of filtering.
Also adjusts the line voltage +/- 10% in 5% increments.
But on battery power it is a modified square wave. Look
at those heatsinks. Do you really think there is enough heatsink
there if this truely was a linear unit.
apc's. Absolutely every unit i have seen going all the way up
to 5000va units are all modified square wave in battery mode.
Many units do run everything thru the transformer in ac mode
and therefore clean up the ac like the best fortress. Some apc
units also do the +/-10% in 5% increment correction.
The only power regeneator i know of that works even half
way decent is the psaudio units, which are class b amplifiers
driving a transformer. Numerous tests on these units with
nasty loads however show how much distortion can be added
to the output when driving things like modern vcr's or dss
receivers, all of which have switching power supplies.
best fortress of various sizes, apc's of various sizes...
Best ferrups. Completely on line unit which consists mainly
of a ferroressonant transformer. It takes over for the few
milliseconds it takes to switch to battery power. Output is
a clipped sine wave under ALL conditions. In addition when
used on loads with nasty power factors, the distortion can
easily exceed 20%. Bundles of thd.
Best fortress are all off line units. When in ac mode everything
does go thru the transformer which does a great job of filtering.
Also adjusts the line voltage +/- 10% in 5% increments.
But on battery power it is a modified square wave. Look
at those heatsinks. Do you really think there is enough heatsink
there if this truely was a linear unit.
apc's. Absolutely every unit i have seen going all the way up
to 5000va units are all modified square wave in battery mode.
Many units do run everything thru the transformer in ac mode
and therefore clean up the ac like the best fortress. Some apc
units also do the +/-10% in 5% increment correction.
The only power regeneator i know of that works even half
way decent is the psaudio units, which are class b amplifiers
driving a transformer. Numerous tests on these units with
nasty loads however show how much distortion can be added
to the output when driving things like modern vcr's or dss
receivers, all of which have switching power supplies.
Elgar
Anyone try the Elgar line of UPLCs (Ultra Precision Line Conditioners)? I've snapped up a few from eBay for not much more than $100 a piece. They boast a THD output spec of <0.20% at 10% THD input and provide, I can verify, a very clean sine wave under any operating condition I've thrown at them (parallelled 2N6259s on the output might have something to do with this result). The only artifacts I can find on the outputs of units I've tested is a small 1MHz noise signal at the limits of my scope.
Elgar's units operate in buck/boost format, like the Accuphase (I'd be speculating to say Accuphase copied Elgar's well-worked design), and are built like a tank using excellent components throughout (for instance, there are only seven electrolytic capacitors in the entire design, the rest being film or PIO).
I have upgraded all parts on a few units, replacing critical components with highest grade varieties, and now would not run my stereo without the two Elgars I use (10 and 30 amp versions). I judge the Elgar superior to PS Audio units, which I've owned. The Elgars are also quite efficient, perhaps surpassing the efficiency of PWM regenerators.
Anyone try the Elgar line of UPLCs (Ultra Precision Line Conditioners)? I've snapped up a few from eBay for not much more than $100 a piece. They boast a THD output spec of <0.20% at 10% THD input and provide, I can verify, a very clean sine wave under any operating condition I've thrown at them (parallelled 2N6259s on the output might have something to do with this result). The only artifacts I can find on the outputs of units I've tested is a small 1MHz noise signal at the limits of my scope.
Elgar's units operate in buck/boost format, like the Accuphase (I'd be speculating to say Accuphase copied Elgar's well-worked design), and are built like a tank using excellent components throughout (for instance, there are only seven electrolytic capacitors in the entire design, the rest being film or PIO).
I have upgraded all parts on a few units, replacing critical components with highest grade varieties, and now would not run my stereo without the two Elgars I use (10 and 30 amp versions). I judge the Elgar superior to PS Audio units, which I've owned. The Elgars are also quite efficient, perhaps surpassing the efficiency of PWM regenerators.
I have a simple question concerning the first post of that thread and "power regeneration" in general:
What is the purpose of generating a sine wave with very low THD and using it to power our audio equipment, when such equipment is just always going to rectify it?
PD: To see the voltage and current waveforms associated with the classic audio PSU that just rectifies a 50Hz or 60Hz waveform coming from a transformer, review this thread: http://www.diyaudio.com/forums/showthread.php?s=&threadid=66542
Note how the voltage waveform is clipped very hard and distorted by the rectification process, particularly with high loads, and note how narrow are the current pulses, thus containing a whole lot of undesirable midrange and trebble frequencies, even when the mains waveform is a pure sine wave.
So, Is there any point in keeping mains THD low?
What is the purpose of generating a sine wave with very low THD and using it to power our audio equipment, when such equipment is just always going to rectify it?
PD: To see the voltage and current waveforms associated with the classic audio PSU that just rectifies a 50Hz or 60Hz waveform coming from a transformer, review this thread: http://www.diyaudio.com/forums/showthread.php?s=&threadid=66542
Note how the voltage waveform is clipped very hard and distorted by the rectification process, particularly with high loads, and note how narrow are the current pulses, thus containing a whole lot of undesirable midrange and trebble frequencies, even when the mains waveform is a pure sine wave.
So, Is there any point in keeping mains THD low?
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