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#11
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Pure Sine Wave UPSes for New Dell PCs
Hi!
Not necessarily. *The PS in the 9000 is rated for 475 Watts and puts out a true 475 Watts. That's not quite what I'm getting at. How well filtered is the input for the supply? How well will it continue to operate under stressful conditions (like a low line voltage)? Meeting the published specifications for output is just one of many criteria. And while most of Dell's power supplies are of good quality, a comparison to something like a PC Power and Cooling unit would make them look cheap and maybe even a little flimsy. Given that Bestec supplies are showing up in some low end Dell boxen, I'd not be surprised to learn that even the higher end machines are having quality cutbacks here. *I've seen some name brand supplies put out less than their rating. Sure. And there are always dishonest no-name makers to worry about as well: http://greyghost.mooo.com/psuthoughts/ That's the first of two that I've seen. After finding another one (in another eMachines computer), I see that whoever made it did do some re- engineering, mostly accomplished by adding more metal to the heatsinks. I guess they hoped this would make the supply live a little bit longer. The second one wouldn't even produce enough power to let the machine operate correctly, and I'd bet it wasn't pushing a load of more than perhaps 80-100 watts across all of its outputs. All problems disappeared upon replacement of the power supply with an honestly specified AGI 350 watt unit. The owner claimed that no one except Best Buy had ever serviced the machine. I don't have a high opinion of their service operations, but I'd hope that they would at least use decent quality, honestly specified replacement parts. William |
#12
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Pure Sine Wave UPSes for New Dell PCs
Hi!
That's not necessarily because my UPS doesn't produce a sine waveform. Actually, it sounds like it's because you turned it off. :-) For one thing, at 550 VA, my UPS is way under-powered. You should get a bigger one. An overloaded UPS won't always take it gracefully. I've seen overloaded UPS units go off with a bang, especially the cheaper ones. For another, this sissy little UPS probably doesn't have a fast enough transfer time. The power supply filter caps should bypass that problem, as they usually hold enough energy to see the power supply past little dips and sags. They only manage to hold about a second or so's worth of energy most of the time. William |
#13
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Pure Sine Wave UPSes for New Dell PCs
William R. Walsh wrote:
Hi! Not necessarily. The PS in the 9000 is rated for 475 Watts and puts out a true 475 Watts. That's not quite what I'm getting at. How well filtered is the input for the supply? How well will it continue to operate under stressful conditions (like a low line voltage)? Meeting the published specifications for output is just one of many criteria. And while most of Dell's power supplies are of good quality, a comparison to something like a PC Power and Cooling unit would make them look cheap and maybe even a little flimsy. Given that Bestec supplies are showing up in some low end Dell boxen, I'd not be surprised to learn that even the higher end machines are having quality cutbacks here. I've seen some name brand supplies put out less than their rating. Sure. And there are always dishonest no-name makers to worry about as well: http://greyghost.mooo.com/psuthoughts/ That's the first of two that I've seen. After finding another one (in another eMachines computer), I see that whoever made it did do some re- engineering, mostly accomplished by adding more metal to the heatsinks. I guess they hoped this would make the supply live a little bit longer. The second one wouldn't even produce enough power to let the machine operate correctly, and I'd bet it wasn't pushing a load of more than perhaps 80-100 watts across all of its outputs. All problems disappeared upon replacement of the power supply with an honestly specified AGI 350 watt unit. The owner claimed that no one except Best Buy had ever serviced the machine. I don't have a high opinion of their service operations, but I'd hope that they would at least use decent quality, honestly specified replacement parts. William This gives me an opportunity to ask this question: Since the 9000 has a PFC power supply - even though a Dell tech support rep assured me that "no Dell computer have PFC supply" - does that mean that its 475 watt power supply really delivers a maximum of 475 watts? Daddy |
#14
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Pure Sine Wave UPSes for New Dell PCs
On Fri, 09 Apr 2010 00:31:04 -0400, Daddy
wrote: Tom Lake wrote: I maintain that Dell is cheapskating on the quality of their power supplies, and they may have a nasty backlash from doing so. (But then again, I'm a pretty big believer in "do it right the first time" for stuff like this.) Not necessarily. The PS in the 9000 is rated for 475 Watts and puts out a true 475 Watts. I've seen some name brand supplies put out less than their rating. Tom L Well, I conducted my little experiment...pressed the power button on my UPS to turn it off, and...my computer and monitor immediately shut off. I assume the UPS battery is not dead ???? That's not necessarily because my UPS doesn't produce a sine waveform. For one thing, at 550 VA, my UPS is way under-powered. For another, this sissy little UPS probably doesn't have a fast enough transfer time. By the way, don't waste your time asking Dell technical support about power supplies or UPSes. They don't have a clue. Thanks for the info but heck, I'd be just happy if I could understand their English when i've called them (admittedly a couple of years ago) much less about UPSs. |
#15
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Pure Sine Wave UPSes for New Dell PCs
Hi!
does that mean that its 475 watt power supply really delivers a maximum of 475 watts? That's not what PFC does. PFC tries to compensate for the fact that the components inside a power supply (particularly the capacitors and inductors) may mess up the relationship of voltage to current in an AC power waveform. In other words, your computer's power supply may be "polluting" the power line. With resistive loads (like heaters and such) the voltage and current are in perfect synchronization with one another, giving these devices a power factor of "1". Depending upon how it is loaded, the power factor of your PC's power supply can change. A passive PFC circuit performs a fixed amount of power factor correction and does not adapt to differing load conditions. Active PFC works by adjusting the level of power factor correction based on how hard the power supply is working. The idea is to get things as close as is possible to a power factor of 1 (the perfect value). Whether your power supply will meet its listed output is another matter entirely. The ratings of each major component--the switching transistors, rectifiers, transformers, capacitors and other stuff-- must be considered. There must also be sufficient cooling for these parts, especially the rectifiers and switching transistors. Otherwise they will go "boom". See my other posting for a comparison of two other power supplies, one of them dishonestly specified. You can easily see how the honestly specified supply has much better build quality--it can more easily dissipate heat and the major components are larger, serving as a rough indicator that they are capable of more work. William |
#16
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Pure Sine Wave UPSes for New Dell PCs
Hi!
It's probably impossible to come up with accurate measurements for the actual inrush current and minimum transfer time of a given power supply. The general rule is to multiply the current rating printed on the nameplate by three. That's your inrush current figure. As that rating is frequently a worst case rating, for a fully loaded machine doing everything at once, you'll have some headroom here. If you could find a meter with a sufficiently fast response time with a "peak hold" function, that could be used to figure it out at as well. A UPS is seldom if ever going to be powering your system from a true cold start (where inrush current would be an issue). Every ATX power supply I have ever seen keeps a small portion of its circuitry alive when plugged in (and the switch at the back, if there is one, turned on). The main filter capacitors are also usually kept charged in this case. So you really only have to be concerned about the average amount of power your system is using. There are inexpensive plug in meters that can tell you all of this quickly and easily. Most have multiple scales of measurement (watts, amps, line voltage, volt amps) that are reasonably accurate. The P3 Kill-A-Watt is one such meter, and it is readily available. One of these can be a very worthwhile investment. Then figure about 20-30% headroom on top of that for your UPS capacity. The way I'd do it is to plug everything into the meter, power up all the equipment you want the UPS to protect, do something that runs your CPU usage up to 100% for a few minutes You should test your UPS periodically. Better units have a button to press for testing (a feature curiously absent from the plug strip types sold by APC, Tripp-Lite and Cyber Power) and even better units conduct timed self tests on a repeating schedule (usually every two weeks). Those that don't have a dedicated "push to test" button can sometimes be tested by pressing and holding the power button for a few seconds. Although I have never had a problem doing so, pulling the plug on your UPS to test it can result in the grounds for each piece of computing equipment entering a "floating" state. This does assume that the grounds are properly connected when the UPS is plugged in, as they should be. (This means that if your UPS has its "site wiring fault" light on, you need to find out why and have the problem fixed.) However, it is a guaranteed test. William |
#17
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Pure Sine Wave UPSes for New Dell PCs
Hi!
(oops!) The way I'd do it is to plug everything into the meter, power up all the equipment you want the UPS to protect, do something that runs your CPU usage up to 100% for a few minutes ...., turn on all peripheral devices and take a reading with your meter set to report volt-amps (because that's how UPS units are rated). Don't put your printer on the UPS. Although inkjet printers are unlikely to cause trouble, laser printers will. The fuser demands an enormous inrush current whenever it fires, and this will overwhelm the inverter in all but the very largest UPS units, causing it to shut down (best case) or fail in an exciting way. William |
#18
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Pure Sine Wave UPSes for New Dell PCs
In article ,
William R. Walsh wrote: Hi! on). The main filter capacitors are also usually kept charged in this case. So you really only have to be concerned about the average amount of power your system is using. There are inexpensive plug in meters that can tell you all of this quickly and easily. I think you are deescribing the"Kill-A-Watt". http://www.amazon.com/P3-Internation.../dp/B00009MDBU seconds. Although I have never had a problem doing so, pulling the plug on your UPS to test it can result in the grounds for each piece of computing equipment entering a "floating" state. This does assume that the grounds are properly connected when the UPS is plugged in, as they should be. (This means that if your UPS has its "site wiring fault" light on, you need to find out why and have the problem fixed.) However, it is a guaranteed test. I know of a case where a UPS wouldn't supply juice if it wasn't plugged into the utility mains. It was a "field day" exercise and the intent was to power a WiFi repeater off the grid. -- Al Dykes News is something someone wants to suppress, everything else is advertising. - Lord Northcliffe, publisher of the Daily Mail |
#19
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Pure Sine Wave UPSes for New Dell PCs
William R. Walsh wrote:
Hi! It's probably impossible to come up with accurate measurements for the actual inrush current and minimum transfer time of a given power supply. The general rule is to multiply the current rating printed on the nameplate by three. That's your inrush current figure. As that rating is frequently a worst case rating, for a fully loaded machine doing everything at once, you'll have some headroom here. If you could find a meter with a sufficiently fast response time with a "peak hold" function, that could be used to figure it out at as well. A UPS is seldom if ever going to be powering your system from a true cold start (where inrush current would be an issue). Every ATX power supply I have ever seen keeps a small portion of its circuitry alive when plugged in (and the switch at the back, if there is one, turned on). The main filter capacitors are also usually kept charged in this case. So you really only have to be concerned about the average amount of power your system is using. There are inexpensive plug in meters that can tell you all of this quickly and easily. Most have multiple scales of measurement (watts, amps, line voltage, volt amps) that are reasonably accurate. The P3 Kill-A-Watt is one such meter, and it is readily available. One of these can be a very worthwhile investment. Then figure about 20-30% headroom on top of that for your UPS capacity. The way I'd do it is to plug everything into the meter, power up all the equipment you want the UPS to protect, do something that runs your CPU usage up to 100% for a few minutes You should test your UPS periodically. Better units have a button to press for testing (a feature curiously absent from the plug strip types sold by APC, Tripp-Lite and Cyber Power) and even better units conduct timed self tests on a repeating schedule (usually every two weeks). Those that don't have a dedicated "push to test" button can sometimes be tested by pressing and holding the power button for a few seconds. Although I have never had a problem doing so, pulling the plug on your UPS to test it can result in the grounds for each piece of computing equipment entering a "floating" state. This does assume that the grounds are properly connected when the UPS is plugged in, as they should be. (This means that if your UPS has its "site wiring fault" light on, you need to find out why and have the problem fixed.) However, it is a guaranteed test. William I have learned several things from this entire exercise: 1- Dell technical support reps don't know what a PFC power supply is, and aren't sure whether any Dell computer has one. 2- Dell technical support reps don't really understand the published specifications for the computers they are supporting. 3- None of the big UPS makers will come out and say: You can't use our home and small office UPSes if your computer has a PFC power supply. 4- None of the formulas, online calculators or techniques to calculate or estimate the correct size UPS for your computer arrive at the same conclusion. 5- Nobody agrees on the correct method to calculate or estimate the correct size UPS. 6- No OEM will tell you: If you are thinking about purchasing this particular computer, consider this: It will require a UPS that will cost you half as much as the computer itself for adequate power protection. 7- No UPS maker will say whether they'll honor their warranty if you use a stepped approximation unit with a PFC power supply. I apologize for ranting. Daddy |
#20
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Pure Sine Wave UPSes for New Dell PCs
On Fri, 09 Apr 2010 14:20:53 -0400, Daddy
wrote: William R. Walsh wrote: Hi! It's probably impossible to come up with accurate measurements for the actual inrush current and minimum transfer time of a given power supply. The general rule is to multiply the current rating printed on the nameplate by three. That's your inrush current figure. As that rating is frequently a worst case rating, for a fully loaded machine doing everything at once, you'll have some headroom here. If you could find a meter with a sufficiently fast response time with a "peak hold" function, that could be used to figure it out at as well. A UPS is seldom if ever going to be powering your system from a true cold start (where inrush current would be an issue). Every ATX power supply I have ever seen keeps a small portion of its circuitry alive when plugged in (and the switch at the back, if there is one, turned on). The main filter capacitors are also usually kept charged in this case. So you really only have to be concerned about the average amount of power your system is using. There are inexpensive plug in meters that can tell you all of this quickly and easily. Most have multiple scales of measurement (watts, amps, line voltage, volt amps) that are reasonably accurate. The P3 Kill-A-Watt is one such meter, and it is readily available. One of these can be a very worthwhile investment. Then figure about 20-30% headroom on top of that for your UPS capacity. The way I'd do it is to plug everything into the meter, power up all the equipment you want the UPS to protect, do something that runs your CPU usage up to 100% for a few minutes You should test your UPS periodically. Better units have a button to press for testing (a feature curiously absent from the plug strip types sold by APC, Tripp-Lite and Cyber Power) and even better units conduct timed self tests on a repeating schedule (usually every two weeks). Those that don't have a dedicated "push to test" button can sometimes be tested by pressing and holding the power button for a few seconds. Although I have never had a problem doing so, pulling the plug on your UPS to test it can result in the grounds for each piece of computing equipment entering a "floating" state. This does assume that the grounds are properly connected when the UPS is plugged in, as they should be. (This means that if your UPS has its "site wiring fault" light on, you need to find out why and have the problem fixed.) However, it is a guaranteed test. William I have learned several things from this entire exercise: 1- Dell technical support reps don't know what a PFC power supply is, and aren't sure whether any Dell computer has one. 2- Dell technical support reps don't really understand the published specifications for the computers they are supporting. 3- None of the big UPS makers will come out and say: You can't use our home and small office UPSes if your computer has a PFC power supply. 4- None of the formulas, online calculators or techniques to calculate or estimate the correct size UPS for your computer arrive at the same conclusion. 5- Nobody agrees on the correct method to calculate or estimate the correct size UPS. 6- No OEM will tell you: If you are thinking about purchasing this particular computer, consider this: It will require a UPS that will cost you half as much as the computer itself for adequate power protection. 7- No UPS maker will say whether they'll honor their warranty if you use a stepped approximation unit with a PFC power supply. I apologize for ranting. Daddy Don't apologize.... this post taught me something grin. |
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