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

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

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

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.

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

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

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

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

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

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.