Home |
Search |
Today's Posts |
|
Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
Reply |
|
LinkBack | Thread Tools | Display Modes |
#1
Posted to sci.electronics.design,alt.comp.hardware,sci.electronics.basics,alt.comp.hardware.pc-homebuilt,sci.electronics.repair
|
|||
|
|||
Power Conversion Electronics
I just purchase a Silverstone Power Supply Unit (PSU) for my PC.
I am amaze with the PFC (Power Factor Correction) rating of over 0.96, which, according to some indicators, means it's 96% efficient. (4% wastage as heat). Since it's a new unit I dare not to open up the PSU to see what type of electronics they are using. So I post the question here ---- Can anyone tell me what type of Power Conversion Electronic Devices they use in those high PFC rating PSU? Thank you all !!! |
#2
Posted to sci.electronics.design,alt.comp.hardware,sci.electronics.basics,alt.comp.hardware.pc-homebuilt,sci.electronics.repair
|
|||
|
|||
Power Conversion Electronics
On Sun, 26 Apr 2009 02:20:26 -0700 (PDT), pg
wrote: I just purchase a Silverstone Power Supply Unit (PSU) for my PC. I am amaze with the PFC (Power Factor Correction) rating of over 0.96, which, according to some indicators, means it's 96% efficient. (4% wastage as heat). PFC and efficiency are not the same thing. http://en.wikipedia.org/wiki/Power_factor_correction http://en.wikipedia.org/wiki/Energy_...ion_efficiency |
#3
Posted to sci.electronics.design,alt.comp.hardware,sci.electronics.repair
|
|||
|
|||
Power Conversion Electronics
pg wrote:
I just purchase a Silverstone Power Supply Unit (PSU) for my PC. I am amaze with the PFC (Power Factor Correction) rating of over 0.96, which, according to some indicators, means it's 96% efficient. (4% wastage as heat). Since it's a new unit I dare not to open up the PSU to see what type of electronics they are using. So I post the question here ---- Can anyone tell me what type of Power Conversion Electronic Devices they use in those high PFC rating PSU? Thank you all !!! Something like this, perhaps http://www.onsemi.com/pub_link/Collateral/NCP1653-D.PDF Sylvia. |
#4
Posted to sci.electronics.design,alt.comp.hardware,sci.electronics.basics,alt.comp.hardware.pc-homebuilt,sci.electronics.repair
|
|||
|
|||
Power Conversion Electronics
On Apr 26, 2:33*am, Ken wrote:
On Sun, 26 Apr 2009 02:20:26 -0700 (PDT), pg wrote: I just purchase a Silverstone Power Supply Unit (PSU) for my PC. I am amaze with the PFC (Power Factor Correction) rating of over 0.96, which, according to some indicators, means it's 96% efficient. (4% wastage as heat). PFC and efficiency are not the same thing.http://en.wikipedia.org/wiki/Power_f...ion_efficiency Many thanks for the info !! |
#5
Posted to sci.electronics.design,alt.comp.hardware,sci.electronics.basics,alt.comp.hardware.pc-homebuilt,sci.electronics.repair
|
|||
|
|||
Power Conversion Electronics
On Sun, 26 Apr 2009 02:20:26 -0700, pg rearranged some electrons to say:
I just purchase a Silverstone Power Supply Unit (PSU) for my PC. I am amaze with the PFC (Power Factor Correction) rating of over 0.96, which, according to some indicators, means it's 96% efficient. (4% wastage as heat). Since it's a new unit I dare not to open up the PSU to see what type of electronics they are using. So I post the question here ---- Can anyone tell me what type of Power Conversion Electronic Devices they use in those high PFC rating PSU? Thank you all !!! 0.96 power factor does not mean 96% efficient. But, to answer your question, active power factor correction means that the front end of the power supply tries to keep the phase between the voltage and current waveforms as small as possible. |
#6
Posted to sci.electronics.design,alt.comp.hardware,sci.electronics.repair
|
|||
|
|||
Power Conversion Electronics
Sylvia Else wrote:
pg wrote: I just purchase a Silverstone Power Supply Unit (PSU) for my PC. I am amaze with the PFC (Power Factor Correction) rating of over 0.96, which, according to some indicators, means it's 96% efficient. (4% wastage as heat). Since it's a new unit I dare not to open up the PSU to see what type of electronics they are using. So I post the question here ---- Can anyone tell me what type of Power Conversion Electronic Devices they use in those high PFC rating PSU? Thank you all !!! Something like this, perhaps http://www.onsemi.com/pub_link/Collateral/NCP1653-D.PDF Sylvia. Hmm.... I wonder how those would handle an input in the form of a "modified sine wave", which would more accurately be described as a modified square wave, as typically produced by cheaper UPSs. An ordinary PC PS wouldn't notice the difference. Sylvia. |
#7
Posted to sci.electronics.design,alt.comp.hardware,sci.electronics.repair
|
|||
|
|||
Power Conversion Electronics
On Apr 26, 7:08*am, Sylvia Else wrote:
Sylvia Else wrote: pg wrote: I just purchase a Silverstone Power Supply Unit (PSU) for my PC. I am amaze with the PFC (Power Factor Correction) rating of over 0.96, which, according to some indicators, means it's 96% efficient. (4% wastage as heat). Since it's a new unit I dare not to open up the PSU to see what type of electronics they are using. So I post the question here ---- Can anyone tell me what type of Power Conversion Electronic Devices they use in those high PFC rating PSU? Thank you all !!! Something like this, perhaps http://www.onsemi.com/pub_link/Collateral/NCP1653-D.PDF Sylvia. Hmm.... I wonder how those would handle an input in the form of a "modified sine wave", which would more accurately be described as a modified square wave, as typically produced by cheaper UPSs. An ordinary PC PS wouldn't notice the difference. Most power factor correction circuit will run on a rounded off square wave without any trouble. In the short term, they watch the input voltage and match the current to that. They don't make their own sine function to match the current to. Sylvia. |
#8
Posted to sci.electronics.design,alt.comp.hardware,sci.electronics.basics,alt.comp.hardware.pc-homebuilt,sci.electronics.repair
|
|||
|
|||
Power Conversion Electronics
On Apr 26, 5:32*am, david wrote:
On Sun, 26 Apr 2009 02:20:26 -0700, pg rearranged some electrons to say: I just purchase a Silverstone Power Supply Unit (PSU) for my PC. I am amaze with the PFC (Power Factor Correction) rating of over 0.96, which, according to some indicators, means it's 96% efficient. (4% wastage as heat). Since it's a new unit I dare not to open up the PSU to see what type of electronics they are using. So I post the question here ---- Can anyone tell me what type of Power Conversion Electronic Devices they use in those high PFC rating PSU? Thank you all !!! 0.96 power factor does not mean 96% efficient. *But, to answer your question, *active power factor correction means that the front end of the power supply tries to keep the phase between the voltage and current waveforms as small as possible. It also tries not to draw any current at harmonics. It is unfortunate that one term is now used for two effects but we are stuck with it. |
#9
Posted to sci.electronics.design,alt.comp.hardware,sci.electronics.basics,alt.comp.hardware.pc-homebuilt,sci.electronics.repair
|
|||
|
|||
Power Conversion Electronics
On Apr 26, 11:33*am, MooseFET wrote:
It also tries not to draw any current at harmonics. *It is unfortunate that one term is now used for two effects but we are stuck with it. Displacement Factor is the fudamental only. Tim |
#10
Posted to sci.electronics.design,alt.comp.hardware,sci.electronics.basics,alt.comp.hardware.pc-homebuilt,sci.electronics.repair
|
|||
|
|||
Power Conversion Electronics
pg wrote:
I just purchase a Silverstone Power Supply Unit (PSU) for my PC. I am amaze with the PFC (Power Factor Correction) rating of over 0.96, which, according to some indicators, means it's 96% efficient. (4% wastage as heat). Since it's a new unit I dare not to open up the PSU to see what type of electronics they are using. So I post the question here ---- Can anyone tell me what type of Power Conversion Electronic Devices they use in those high PFC rating PSU? Please do not confuse Power Factor Correction (PFC) with power supply efficiency. They are two separate items. PFC can be either active or passive, but usually alters the highly capacitive input of SMPSs. Google "PFC". |
#11
Posted to sci.electronics.repair
|
|||
|
|||
Power Conversion Electronics -- Power-factor correction forswitchmode PSes
On Sun, 26 Apr 2009 19:39:23 +1000, Sylvia Else wrote:
http://www.onsemi.com/pub_link/Collateral/NCP1653-D.PDF Sylvia. Most interesting! I'd been wondering how it's done. Basic circuit is quite simple. Although I didn't read carefully, it seems that only at the end did I learn that it can provide 300 VDC to the inverter; wasn't sure until then whether the complete circuit was for low voltage output. I'd guess that total component cost is pretty modest. Regards, nb |
#12
Posted to sci.electronics.design,alt.comp.hardware,sci.electronics.basics,alt.comp.hardware.pc-homebuilt,sci.electronics.repair
|
|||
|
|||
Power Conversion Electronics
"UCLAN" Please do not confuse Power Factor Correction (PFC) with power supply efficiency. They are two separate items. ** OK so far. PFC can be either active or passive, ** Hmmmm... but usually alters the highly capacitive input of SMPSs. ** TOTAL ******** !!! They are not capacitive, there is no phase angle. Active PFCs correct WAVEFORM distortion. ....... Phil |
#13
Posted to sci.electronics.design,alt.comp.hardware,sci.electronics.basics,alt.comp.hardware.pc-homebuilt,sci.electronics.repair
|
|||
|
|||
Power Conversion Electronics
On Mon, 27 Apr 2009 12:22:11 +1000, "Phil Allison"
wrote: "UCLAN" Please do not confuse Power Factor Correction (PFC) with power supply efficiency. They are two separate items. ** OK so far. PFC can be either active or passive, ** Hmmmm... but usually alters the highly capacitive input of SMPSs. ** TOTAL ******** !!! They are not capacitive, there is no phase angle. Active PFCs correct WAVEFORM distortion. ...... Phil Take you meds and lie down for a while. What he said was perfectly reasonable. John |
#14
Posted to sci.electronics.design,alt.comp.hardware,sci.electronics.basics,alt.comp.hardware.pc-homebuilt,sci.electronics.repair
|
|||
|
|||
Power Conversion Electronics
"John Larkin" "Phil Allison" "UCLAN" Please do not confuse Power Factor Correction (PFC) with power supply efficiency. They are two separate items. ** OK so far. PFC can be either active or passive, ** Hmmmm... but usually alters the highly capacitive input of SMPSs. ** TOTAL ******** !!! They are not capacitive, there is no phase angle. Active PFCs correct WAVEFORM distortion. Take you meds and lie down for a while. ** Drop dead. What he said was perfectly reasonable. ** It was totally FALSE , you insane ****head. ...... Phil |
#15
Posted to sci.electronics.design,alt.comp.hardware,sci.electronics.repair
|
|||
|
|||
Power Conversion Electronics
Phil Allison wrote:
"UCLAN" Please do not confuse Power Factor Correction (PFC) with power supply efficiency. They are two separate items. ** OK so far. PFC can be either active or passive, ** Hmmmm... but usually alters the highly capacitive input of SMPSs. ** TOTAL ******** !!! They are not capacitive, there is no phase angle. Active PFCs correct WAVEFORM distortion. If you take the waveform of the current into a conventional SMPS, and split it into its harmonics, you'll find that the fundamental leads the voltage. This because the PS's capacitor is charged during the rising side of the input waveform. Looks like a phase angle to me. By making the current proportional to the voltage, active PFCs both minimise the waveform distortion, and correct the phase angle. Sylvia. |
#16
Posted to sci.electronics.design,alt.comp.hardware,sci.electronics.basics,alt.comp.hardware.pc-homebuilt,sci.electronics.repair
|
|||
|
|||
Power Conversion Electronics
On Sun, 26 Apr 2009 02:20:26 -0700, pg wrote:
I just purchase a Silverstone Power Supply Unit (PSU) for my PC. I am amaze with the PFC (Power Factor Correction) rating of over 0.96, which, according to some indicators, means it's 96% efficient. (4% wastage as heat). As others have already pointed out, 0.96 power factor doesn't mean 96% efficient. Power factor does have a slight impact upon efficiency, as a low power factor increases the energy wasted in the power lines, but this is small compared to the energy actually used by the supply. Since it's a new unit I dare not to open up the PSU to see what type of electronics they are using. So I post the question here ---- Can anyone tell me what type of Power Conversion Electronic Devices they use in those high PFC rating PSU? Active PFC involves using a boost converter whose current draw is sinusoidal and in phase with the voltage. For more detail than you probably wanted to know, see: http://www.onsemi.com/pub_link/Collateral/HBD853-D.PDF |
#17
Posted to sci.electronics.design,alt.comp.hardware,sci.electronics.basics,alt.comp.hardware.pc-homebuilt,sci.electronics.repair
|
|||
|
|||
Power Conversion Electronics
On Apr 26, 8:29*pm, Nobody wrote:
On Sun, 26 Apr 2009 02:20:26 -0700, pg wrote: I just purchase a Silverstone Power Supply Unit (PSU) for my PC. I am amaze with the PFC (Power Factor Correction) rating of over 0.96, which, according to some indicators, means it's 96% efficient. (4% wastage as heat). As others have already pointed out, 0.96 power factor doesn't mean 96% efficient. Power factor does have a slight impact upon efficiency, as a low power factor increases the energy wasted in the power lines, but this is small compared to the energy actually used by the supply. Since it's a new unit I dare not to open up the PSU to see what type of electronics they are using. So I post the question here ---- Can anyone tell me what type of Power Conversion Electronic Devices they use in those high PFC rating PSU? Active PFC involves using a boost converter whose current draw is sinusoidal and in phase with the voltage. For more detail than you probably wanted to know, see: * * * *http://www.onsemi.com/pub_link/Collateral/HBD853-D.PDF Thanks a lot for the link !! |
#18
Posted to sci.electronics.design,alt.comp.hardware,sci.electronics.basics,alt.comp.hardware.pc-homebuilt,sci.electronics.repair
|
|||
|
|||
Power Conversion Electronics
Phil Allison wrote:
Please do not confuse Power Factor Correction (PFC) with power supply efficiency. They are two separate items. ** OK so far. Gee, thanks. [Red flag warning!!!] PFC can be either active or passive, ** Hmmmm... Careful, a hint of ignorance is showing. but usually alters the highly capacitive input of SMPSs. ** TOTAL ******** !!! They are not capacitive, there is no phase angle. And it's finally out. He's a total loon. There is a big 400vdc capacitor (or two 200vdc caps in series) just after input rectifiers on the AC input. Note C5 and C6 on: http://www.pavouk.org/hw/en_atxps.html They charge to the peak value of the input AC voltage, or 1.414 times the RMS value. Since the cap(s) draw their maximum current when at lowest charge (zero cross-over point), and draw their least amount of current when charged to their highest point, the current waveform *leads* the voltage waveform by 90 degrees. [Maximum current is at the same time as minimum voltage; minimum current is at the same time as maximum voltage.] |
#19
Posted to sci.electronics.design,alt.comp.hardware,sci.electronics.basics,alt.comp.hardware.pc-homebuilt,sci.electronics.repair
|
|||
|
|||
Power Conversion Electronics
"UCLAN" = the Original Monkey's Uncle. Phil Allison wrote: Please do not confuse Power Factor Correction (PFC) with power supply efficiency. They are two separate items. ** OK so far. Gee, thanks. [Red flag warning!!!] PFC can be either active or passive, ** Hmmmm... Careful, a hint of ignorance is showing. but usually alters the highly capacitive input of SMPSs. ** TOTAL ******** !!! They are not capacitive, there is no phase angle. And it's finally out. He's a total loon. ** This arrogant IMBECILE is about to get a lesson !!! There is a big 400vdc capacitor (or two 200vdc caps in series) just after input rectifiers on the AC input. ** And because they are * AFTER * the rectifiers there is NO cap reactance or phase angle effects involved. They charge to the peak value of the input AC voltage, or 1.414 times the RMS value. ** The caps can only draw current when the diodes are forward biased and cannot pass any current back to the supply. Negates all capacitive reactance effects. Since the cap(s) draw their maximum current when at lowest charge (zero cross-over point), ** 100% ****ING WRONG !!!!!!!!!!! The caps can only draw charging current when the AC supply voltage is greater than the voltage already on the cap - so ( aside from the very first cycle ) they charge at AC voltage peaks ONLY !!!!!!!! and draw their least amount of current when charged to their highest point, ** Insane CRAP !!!!!!!!!!!!!!! Even one moment's intelligent thought shows that simply CANNOT be true. the current waveform *leads* the voltage waveform by 90 degrees. ** Absolute ******** !!! Max current draw **coincides** with peak AC voltage - there is ZERO phase angle. Time for you to go play with the demented Orang-utans - DICKHEAD !! ...... Phil |
#20
Posted to sci.electronics.design,alt.comp.hardware,sci.electronics.basics,alt.comp.hardware.pc-homebuilt,sci.electronics.repair
|
|||
|
|||
Power Conversion Electronics
On Mon, 27 Apr 2009 17:14:51 +1000, "Phil Allison"
wrote: "UCLAN" = the Original Monkey's Uncle. Phil Allison wrote: Please do not confuse Power Factor Correction (PFC) with power supply efficiency. They are two separate items. ** OK so far. Gee, thanks. [Red flag warning!!!] PFC can be either active or passive, ** Hmmmm... Careful, a hint of ignorance is showing. but usually alters the highly capacitive input of SMPSs. ** TOTAL ******** !!! They are not capacitive, there is no phase angle. And it's finally out. He's a total loon. ** This arrogant IMBECILE is about to get a lesson !!! Maybe, but you are still a total loon (!!!) Since the cap(s) draw their maximum current when at lowest charge (zero cross-over point), ** 100% ****ING WRONG !!!!!!!!!!! When one uses this many apostrophies, it is customary to ask Vanna for a vowel and pay for each. You have not done so, and so it is detracting from your attempted point. The caps can only draw charging current when the AC supply voltage is greater than the voltage already on the cap - so ( aside from the very first cycle ) they charge at AC voltage peaks ONLY !!!!!!!! Ok !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!! Time for you to go play with the demented Orang-utans Wait, are you saying we now have a petting zoo? cool!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!! Which cage are you in, I will stop by and throw you a peanut. And some lithium. |
#21
Posted to sci.electronics.design,alt.comp.hardware,sci.electronics.basics,alt.comp.hardware.pc-homebuilt,sci.electronics.repair
|
|||
|
|||
Power Conversion Electronics
"kony" ** No man is an island ...... ..... Phil |
#22
Posted to sci.electronics.design,alt.comp.hardware,sci.electronics.basics,alt.comp.hardware.pc-homebuilt,sci.electronics.repair
|
|||
|
|||
Power Conversion Electronics
kony wrote: Which cage are you in, I will stop by and throw you a peanut. And some lithium. Throw him some Dilitium. His mind needs a recharge. ;-) -- You can't have a sense of humor, if you have no sense! |
#23
Posted to sci.electronics.design,alt.comp.hardware,sci.electronics.basics,alt.comp.hardware.pc-homebuilt,sci.electronics.repair
|
|||
|
|||
Power Conversion Electronics
Phil Allison wrote:
** This arrogant IMBECILE is about to get a lesson !!! I suggest you do a little reading. Start with: http://www.fairchildsemi.com/an/AN/AN-42047.pdf Until then, I suggest you get back on your meds - quickly. |
#24
Posted to sci.electronics.design,alt.comp.hardware,sci.electronics.basics,alt.comp.hardware.pc-homebuilt,sci.electronics.repair
|
|||
|
|||
Power Conversion Electronics
John Larkin wrote:
"Phil Allison" wrote: .... snip ... ** TOTAL ******** !!! They are not capacitive, there is no phase angle. Active PFCs correct WAVEFORM distortion. Take you meds and lie down for a while. What he said was perfectly reasonable. Also, kindly give a complete description about how you determine that an isolated waveform is distorted? -- [mail]: Chuck F (cbfalconer at maineline dot net) [page]: http://cbfalconer.home.att.net Try the download section. |
#25
Posted to sci.electronics.design,alt.comp.hardware,sci.electronics.basics,alt.comp.hardware.pc-homebuilt,sci.electronics.repair
|
|||
|
|||
Power Conversion Electronics
Phil Allison wrote:
"John Larkin" .... snip ... Take you meds and lie down for a while. ** Drop dead. What he said was perfectly reasonable. ** It was totally FALSE , you insane ****head. I suspect he failed to follow your advice, above. It doesn't appear to have improved his language, either. -- [mail]: Chuck F (cbfalconer at maineline dot net) [page]: http://cbfalconer.home.att.net Try the download section. |
#26
Posted to sci.electronics.design,alt.comp.hardware,sci.electronics.basics,alt.comp.hardware.pc-homebuilt,sci.electronics.repair
|
|||
|
|||
Power Conversion Electronics
"UCLAN" = Monkey's Uncle ** This arrogant IMBECILE has had his lesson. But he didn't learn anything - cos he is a congenital ****wit. ....... Phil |
#27
Posted to sci.electronics.basics,alt.comp.hardware.pc-homebuilt,sci.electronics.repair
|
|||
|
|||
Power Conversion Electronics
On Sun, 26 Apr 2009 22:48:56 -0700, UCLAN put
finger to keyboard and composed: There is a big 400vdc capacitor (or two 200vdc caps in series) just after input rectifiers on the AC input. Note C5 and C6 on: http://www.pavouk.org/hw/en_atxps.html They charge to the peak value of the input AC voltage, or 1.414 times the RMS value. Since the cap(s) draw their maximum current when at lowest charge (zero cross-over point), and draw their least amount of current when charged to their highest point, the current waveform *leads* the voltage waveform by 90 degrees. [Maximum current is at the same time as minimum voltage; minimum current is at the same time as maximum voltage.] As much as I dislike the man, he's right. Look at Fig 6 on page 2 of the application note you linked to elsewhere in this thread. PA could easily put at end to this argument by enlightening everyone with his own example ... http://groups.google.com/group/aus.e...e=source&hl=en .... but instead he chooses to elevate himself by demeaning others. - Franc Zabkar -- Please remove one 'i' from my address when replying by email. |
#28
Posted to sci.electronics.basics,alt.comp.hardware.pc-homebuilt,sci.electronics.repair
|
|||
|
|||
Power Conversion Electronics
Franc Zabkar wrote: On Sun, 26 Apr 2009 22:48:56 -0700, UCLAN put finger to keyboard and composed: There is a big 400vdc capacitor (or two 200vdc caps in series) just after input rectifiers on the AC input. Note C5 and C6 on: http://www.pavouk.org/hw/en_atxps.html They charge to the peak value of the input AC voltage, or 1.414 times the RMS value. Since the cap(s) draw their maximum current when at lowest charge (zero cross-over point), and draw their least amount of current when charged to their highest point, the current waveform *leads* the voltage waveform by 90 degrees. [Maximum current is at the same time as minimum voltage; minimum current is at the same time as maximum voltage.] As much as I dislike the man, he's right. He is. Actually, from modelling, I've found a big hulky inductor between the rectifier and storage caps is pretty good at correcting harmonics. Trouble is, they're big, heavy and expensive. Sadly active PFC produces even more RF 'hash' that needs to be dealt with. Look at Fig 6 on page 2 of the application note you linked to elsewhere in this thread. PA could easily put at end to this argument by enlightening everyone with his own example ... http://groups.google.com/group/aus.e...e=source&hl=en ... but instead he chooses to elevate himself by demeaning others. Sadly so. Graham |
#29
Posted to sci.electronics.basics,alt.comp.hardware.pc-homebuilt,sci.electronics.repair
|
|||
|
|||
Power Conversion Electronics
Franc Zabkar wrote:
On Sun, 26 Apr 2009 22:48:56 -0700, UCLAN put finger to keyboard and composed: There is a big 400vdc capacitor (or two 200vdc caps in series) just after input rectifiers on the AC input. Note C5 and C6 on: http://www.pavouk.org/hw/en_atxps.html They charge to the peak value of the input AC voltage, or 1.414 times the RMS value. Since the cap(s) draw their maximum current when at lowest charge (zero cross-over point), and draw their least amount of current when charged to their highest point, the current waveform *leads* the voltage waveform by 90 degrees. [Maximum current is at the same time as minimum voltage; minimum current is at the same time as maximum voltage.] As much as I dislike the man, he's right. Look at Fig 6 on page 2 of the application note you linked to elsewhere in this thread. It does show that the current leads - look at how it's not positioned symmetrically about the 90 degree point, for example. It's not a 90 degree lead, of course, but it's still a lead. Mind you, I think the graph is wrong. When it's flowing, the current into a capactor should be proportional to the rate of change of voltage. So you should see a rapid rise once the input voltage goes above that already on the capacitor, followed by a progressive reduction towards zero (plus the load current) at the voltage peak. I suppose you'd get something closer to what's shown if there were an inductor in series with the supply. Sylvia. |
#30
Posted to sci.electronics.basics,alt.comp.hardware.pc-homebuilt,sci.electronics.repair
|
|||
|
|||
Power Conversion Electronics
On Wed, 29 Apr 2009 12:28:36 +1000, Sylvia Else
put finger to keyboard and composed: Franc Zabkar wrote: On Sun, 26 Apr 2009 22:48:56 -0700, UCLAN put finger to keyboard and composed: There is a big 400vdc capacitor (or two 200vdc caps in series) just after input rectifiers on the AC input. Note C5 and C6 on: http://www.pavouk.org/hw/en_atxps.html They charge to the peak value of the input AC voltage, or 1.414 times the RMS value. Since the cap(s) draw their maximum current when at lowest charge (zero cross-over point), and draw their least amount of current when charged to their highest point, the current waveform *leads* the voltage waveform by 90 degrees. [Maximum current is at the same time as minimum voltage; minimum current is at the same time as maximum voltage.] As much as I dislike the man, he's right. Look at Fig 6 on page 2 of the application note you linked to elsewhere in this thread. It does show that the current leads - look at how it's not positioned symmetrically about the 90 degree point, for example. It's not a 90 degree lead, of course, but it's still a lead. A bigger capacitor would result in less ripple, which means less lead. If you were relying on intuition alone, you would expect that the PF would move closer to unity. In fact the PF actually becomes worse. See the calculations in Phil's example. - Franc Zabkar -- Please remove one 'i' from my address when replying by email. |
#31
Posted to sci.electronics.basics,alt.comp.hardware.pc-homebuilt,sci.electronics.repair
|
|||
|
|||
Power Conversion Electronics
Franc Zabkar wrote:
On Wed, 29 Apr 2009 12:28:36 +1000, Sylvia Else put finger to keyboard and composed: Franc Zabkar wrote: On Sun, 26 Apr 2009 22:48:56 -0700, UCLAN put finger to keyboard and composed: There is a big 400vdc capacitor (or two 200vdc caps in series) just after input rectifiers on the AC input. Note C5 and C6 on: http://www.pavouk.org/hw/en_atxps.html They charge to the peak value of the input AC voltage, or 1.414 times the RMS value. Since the cap(s) draw their maximum current when at lowest charge (zero cross-over point), and draw their least amount of current when charged to their highest point, the current waveform *leads* the voltage waveform by 90 degrees. [Maximum current is at the same time as minimum voltage; minimum current is at the same time as maximum voltage.] As much as I dislike the man, he's right. Look at Fig 6 on page 2 of the application note you linked to elsewhere in this thread. It does show that the current leads - look at how it's not positioned symmetrically about the 90 degree point, for example. It's not a 90 degree lead, of course, but it's still a lead. A bigger capacitor would result in less ripple, which means less lead. If you were relying on intuition alone, you would expect that the PF would move closer to unity. In fact the PF actually becomes worse. With a larger capacitor, you get less lead, but higher instantaneous currents. My intuition would be that the net result is far from obvious. However, the higher current for shorter periods means higher harmonic currents, which don't contribute to the power, so it wouldn't surprise me that the PF would go down. Sylvia. |
Reply |
Thread Tools | Search this Thread |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Forum | |||
SPICE for Power Electronics and Electric Power | Metalworking | |||
SPICE for Power Electronics and Electric Power | Home Repair | |||
power conversion | UK diy | |||
power conversion | UK diy | |||
buy electronics, sell electronics , auction electronics new, used electronics marketplace rHnI | Electronics Repair |