Inverters vs wallwarts...

[bob prohaska]

I\'m setting up a UPS for my computer/comms equipment using an
inverter/charger and battery from Amazon. The equipment draw
is only about 40 watts measured with a Kill-A-Watt, but all
the associated wallwarts use capacitive-input switching power
supplies. That means they only draw current at line peaks.

My seat-of-the-pants guess is that the duty cycle is around 10%,
meaning that the average 40 watts is really 400 watts 10% of the time.
That\'s well within the continuous power rating of the inverter, which
is 800 watts, so it\'s likely the setup will work as it is.

The question is: Can the peak load be made closer to the average
load by putting an inductor in the AC line feeding the wallwarts?

If anybody\'s been through this exercise I\'d be grateful for guidance.

Thanks for reading,

bob prohaska

 

[Phil Allison]

WITLESS whit3rd wrote:
=================

AIUI, current into a capacitor is dv/dt x C, so the square wave should
be much worse in terms of peak current than my sine-wave case.

** Nope - a rectified square wave is pure DC.
SMPSs used in pro-audio power amps are nearly all square wave inverters.
If the load on an AC source were a capacitor, you\'d get
current= dv/dt x C, and if the load were a rectifier into a (capacitor in parallel with a resistor)
you\'d get something more benign. In a power brick, the load is a rectifier and (resistor-loaded?)
regulator, like a capacitor in parallel with a current sink.

The ramp up when the rectifier diodes turn on will be abrupt, lots of peak current,
which was what the inductor was intended to moderate.

If the hypothetical inductor saturates, it\'ll make a buzzing sound; that\'s annoying.

** Context and relevance are not to be found in this fool\'s dictionary.


..... Phil

 

[server]

On Thu, 30 Jun 2022 09:25:24 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

Clifford Heath wrote:
On 30/6/22 05:38, Phil Hobbs wrote:
Even in an inviscid, incompressible fluid, the equations aren\'t all
that simple.  Forced-air cooling of macroscopic systems runs at some
huge and highly variable Reynolds number, depending on where you are.

Pretty sure that Reynolds number cannot be defined for an inviscid
liquid. But yeah, turbulent flows are difficult however you look at them.

My point exactly.

Cheers

Phil Hobbs

Sure. But is my plate 0.2 k/w, or is it 20 k/w?

 

[Jan Panteltje]

On a sunny day (Sat, 25 Jun 2022 20:22:46 -0700 (PDT)) it happened whit3rd
<whit3rd@gmail.com> wrote in
<682a4161-f73e-4b7f-ad78-9237c4291e62n@googlegroups.com>:

On Saturday, June 25, 2022 at 3:10:38 PM UTC-7, palli...@gmail.com wrote:
bob prohaska wrote:

AIUI, current into a capacitor is dv/dt x C, so the square wave should
be much worse in terms of peak current than my sine-wave case.

** Nope - a rectified square wave is pure DC.
SMPSs used in pro-audio power amps are nearly all square wave inverters.

If the load on an AC source were a capacitor, you\'d get
current= dv/dt x C, and if the load were a rectifier into a (capacitor in parallel with a resistor)
you\'d get something more benign. In a power brick, the load is a rectifier and (resistor-loaded?)
regulator, like a capacitor in parallel with a current sink.

The ramp up when the rectifier diodes turn on will be abrupt, lots of peak current,
which was what the inductor was intended to moderate.

If the hypothetical inductor saturates, it\'ll make a buzzing sound; that\'s annoying.

In the UPS case you do not charge into an _empty_ capacitor, if the UPS functions right
then it is just the discharge difference from the last mains period (depends on wallwart load),
the peak current will be limited also by the resistance of the series diodes,
and by the Zi from the UPS etc..
Square wave charges for a longer time, so next period less drop to correct than with a sine...

 

[server]

On Thu, 30 Jun 2022 09:51:22 -0400, legg <legg@nospam.magma.ca> wrote:

On Wed, 29 Jun 2022 19:36:21 -0700, jlarkin@highlandsniptechnology.com
wrote:

On Wed, 29 Jun 2022 18:14:22 -0400, legg <legg@nospam.magma.ca> wrote:

Anyways, wade through it and you may come up with
something like this:

http://ve3ute.ca/query/Polycarbonate_Current_100KHz_Philips.pdf

It will be different for each dielectric, frequency of operation,
temperature etc.

RL

Gosh, real numbers. Thanks.

I just got this. It\'s a high voltage half-bridge test board for frying
inductors and film caps. People were doing another proto board so I
hung this on the end as a v-score breakaway.

https://www.dropbox.com/s/2x8z6yn29ab57xf/Z524_Wing_1.jpg?raw=1

One good way of frying film caps is to thermally couple them
to hot chokes or power resistors.

That\'s inelegant. I plan to pump in amps of 250 KHz triangle wave.

Like a lot of other parts, they depend on thermal conduction
to the PCB.

We will have a lot of forced air flow, at least 200 f/m acoss both
sides of our plugin boards. That will reduce cap temp rise by at least
a factor of 2.

Power resistor data sheets sometimes mention power vs air flow. I have
seen suggestions of between 2:1 and 10:1 more power with air flow.

I\'ll fire up the board and pump amps into various 4.7u radial film
caps, blow some air on them, and measure temps. What else is a boy to
do?

I should try to evaluate how much cooling we might get through the
leads. We could use big power pours on the pins to slurp out some
heat. My first guess is that lead cooling will be minor.

 

[Phil Allison]

Jan Panteltje wrote:

=====================

In the UPS case you do not charge into an _empty_ capacitor, if the UPS functions right
then it is just the discharge difference from the last mains period (depends on wallwart load),
the peak current will be limited also by the resistance of the series diodes,
and by the Zi from the UPS etc..

**Yep.

> Square wave charges for a longer time,

** Nonsense.

No charging pulses AT ALL.
It\'s fucking DC you fool.



...... Phil

 

[legg]

On Sun, 26 Jun 2022 05:00:35 -0700 (PDT), Phil Allison
<pallison49@gmail.com> wrote:

Jan Panteltje wrote:

=====================

In the UPS case you do not charge into an _empty_ capacitor, if the UPS functions right
then it is just the discharge difference from the last mains period (depends on wallwart load),
the peak current will be limited also by the resistance of the series diodes,
and by the Zi from the UPS etc..

**Yep.

Square wave charges for a longer time,

** Nonsense.

No charging pulses AT ALL.
It\'s fucking DC you fool.



..... Phil

They\'re talking about wallwarts loading the output of
a UPS inverter that generates a 120VAC output with either
a square or sine waveform.

Capacitive rectified input filters of the wallwarts\'
primary(SMPS), or capacitive rectified output filters
of the wallwart\'s (linear) secondaries will produce a
different 120VAC current crest factor, depending on
whether they are fed by a square or sine wave.

If a square wave has it\'s simplest form (+-120V ~180degree,
then crest factor is low, but the capacitive rectified
output voltage will be only 70% of that produced by a 120V
sine source.

If the square vave is tailored to produce a more similar
output (peak to RMS ratio), with higher voltage at a
reduced duty cycle, then crest factor of rectified current
will increase, and can easily exceed that of the sinusoidal
standard input. Input current will look more like an RC
charge/discharge, than a haversine charge/RC discharge.

RL

 

[Jan Panteltje]

On a sunny day (Sun, 26 Jun 2022 08:43:40 -0400) it happened legg
<legg@nospam.magma.ca> wrote in <9jjgbhhjkqbqjr4krsm1g9dco3oc495k2d@4ax.com>:

On Sun, 26 Jun 2022 05:00:35 -0700 (PDT), Phil Allison
pallison49@gmail.com> wrote:

Jan Panteltje wrote:

=====================

In the UPS case you do not charge into an _empty_ capacitor, if the UPS functions right
then it is just the discharge difference from the last mains period (depends on wallwart load),
the peak current will be limited also by the resistance of the series diodes,
and by the Zi from the UPS etc..

**Yep.

Square wave charges for a longer time,

** Nonsense.

No charging pulses AT ALL.
It\'s fucking DC you fool.



..... Phil

They\'re talking about wallwarts loading the output of
a UPS inverter that generates a 120VAC output with either
a square or sine waveform.

Capacitive rectified input filters of the wallwarts\'
primary(SMPS), or capacitive rectified output filters
of the wallwart\'s (linear) secondaries will produce a
different 120VAC current crest factor, depending on
whether they are fed by a square or sine wave.

If a square wave has it\'s simplest form (+-120V ~180degree,
then crest factor is low, but the capacitive rectified
output voltage will be only 70% of that produced by a 120V
sine source.

If the square vave is tailored to produce a more similar
output (peak to RMS ratio), with higher voltage at a
reduced duty cycle, then crest factor of rectified current
will increase, and can easily exceed that of the sinusoidal
standard input. Input current will look more like an RC
charge/discharge, than a haversine charge/RC discharge.

RL

Here the waveform of my cheap UPS loaded with a normal 25 W lightbulb:
http://www.panteltje.com/pub/APC_UPS_ES700_waveform_25W_edison_bulb_load_IMG_0270.JPG

measured a while back when it was new,
230V AC 50Hz Europe, cannot read the Vpp from the picture
but 230 * sqrt(2) = 325, *2 = 650 Vpp
this looks like 5 to 6 divisions maybe around 500 to 600 Vpp (not sure).
Waveform is interesting

 

[legg]

On Sun, 26 Jun 2022 13:29:08 GMT, Jan Panteltje
<pNaonStpealmtje@yahoo.com> wrote:

On a sunny day (Sun, 26 Jun 2022 08:43:40 -0400) it happened legg
legg@nospam.magma.ca> wrote in <9jjgbhhjkqbqjr4krsm1g9dco3oc495k2d@4ax.com>:

On Sun, 26 Jun 2022 05:00:35 -0700 (PDT), Phil Allison
pallison49@gmail.com> wrote:

Jan Panteltje wrote:

=====================

In the UPS case you do not charge into an _empty_ capacitor, if the UPS functions right
then it is just the discharge difference from the last mains period (depends on wallwart load),
the peak current will be limited also by the resistance of the series diodes,
and by the Zi from the UPS etc..

**Yep.

Square wave charges for a longer time,

** Nonsense.

No charging pulses AT ALL.
It\'s fucking DC you fool.



..... Phil

They\'re talking about wallwarts loading the output of
a UPS inverter that generates a 120VAC output with either
a square or sine waveform.

Capacitive rectified input filters of the wallwarts\'
primary(SMPS), or capacitive rectified output filters
of the wallwart\'s (linear) secondaries will produce a
different 120VAC current crest factor, depending on
whether they are fed by a square or sine wave.

If a square wave has it\'s simplest form (+-120V ~180degree,
then crest factor is low, but the capacitive rectified
output voltage will be only 70% of that produced by a 120V
sine source.

If the square vave is tailored to produce a more similar
output (peak to RMS ratio), with higher voltage at a
reduced duty cycle, then crest factor of rectified current
will increase, and can easily exceed that of the sinusoidal
standard input. Input current will look more like an RC
charge/discharge, than a haversine charge/RC discharge.

RL

Here the waveform of my cheap UPS loaded with a normal 25 W lightbulb:
http://www.panteltje.com/pub/APC_UPS_ES700_waveform_25W_edison_bulb_load_IMG_0270.JPG

measured a while back when it was new,
230V AC 50Hz Europe, cannot read the Vpp from the picture
but 230 * sqrt(2) = 325, *2 = 650 Vpp
this looks like 5 to 6 divisions maybe around 500 to 600 Vpp (not sure).
Waveform is interesting

That\'s the modified square wave. It will produce quite peaky
current waveforms in a capacitive rectified filter.

But, as you\'ve said, if it works, it works. The OP was trying to
predict performance, based on insufficient information.

RL

 

[Phil Hobbs]

jlarkin@highlandsniptechnology.com wrote:

On Thu, 30 Jun 2022 09:25:24 -0400, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

Clifford Heath wrote:
On 30/6/22 05:38, Phil Hobbs wrote:
Even in an inviscid, incompressible fluid, the equations aren\'t all
that simple.  Forced-air cooling of macroscopic systems runs at some
huge and highly variable Reynolds number, depending on where you are.

Pretty sure that Reynolds number cannot be defined for an inviscid
liquid. But yeah, turbulent flows are difficult however you look at them.

My point exactly.


Sure. But is my plate 0.2 k/w, or is it 20 k/w?

A zero-order approximation would be to assume that the boundary layer is
~5 mm thick, and the plate behaves like still air of that thickness
connected to an infinite heat sink at the outlet temperature.

You can compute the outlet temperature using the mass flow rate, heat
capacity of air, inlet temperature, and power dissipation.

I\'d expect things to improve faster than linearly with flow rate,
because the boundary layer should thin down as well as the outlet
temperature falling.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

 

[Phil Hobbs]

jlarkin@highlandsniptechnology.com wrote:

On Thu, 30 Jun 2022 09:51:22 -0400, legg <legg@nospam.magma.ca> wrote:

On Wed, 29 Jun 2022 19:36:21 -0700, jlarkin@highlandsniptechnology.com
wrote:

On Wed, 29 Jun 2022 18:14:22 -0400, legg <legg@nospam.magma.ca> wrote:

Anyways, wade through it and you may come up with
something like this:

http://ve3ute.ca/query/Polycarbonate_Current_100KHz_Philips.pdf

It will be different for each dielectric, frequency of operation,
temperature etc.

RL

Gosh, real numbers. Thanks.

I just got this. It\'s a high voltage half-bridge test board for frying
inductors and film caps. People were doing another proto board so I
hung this on the end as a v-score breakaway.

https://www.dropbox.com/s/2x8z6yn29ab57xf/Z524_Wing_1.jpg?raw=1

One good way of frying film caps is to thermally couple them
to hot chokes or power resistors.

That\'s inelegant. I plan to pump in amps of 250 KHz triangle wave.


Like a lot of other parts, they depend on thermal conduction
to the PCB.

We will have a lot of forced air flow, at least 200 f/m acoss both
sides of our plugin boards. That will reduce cap temp rise by at least
a factor of 2.

Power resistor data sheets sometimes mention power vs air flow. I have
seen suggestions of between 2:1 and 10:1 more power with air flow.

I\'ll fire up the board and pump amps into various 4.7u radial film
caps, blow some air on them, and measure temps. What else is a boy to
do?

I should try to evaluate how much cooling we might get through the
leads. We could use big power pours on the pins to slurp out some
heat. My first guess is that lead cooling will be minor.

Film and foil caps work a lot better for that sort of use than
metallized-film ones.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

 

[server]

On Sun, 26 Jun 2022 10:27:49 -0400, legg <legg@nospam.magma.ca> wrote:

On Sun, 26 Jun 2022 13:29:08 GMT, Jan Panteltje
pNaonStpealmtje@yahoo.com> wrote:

On a sunny day (Sun, 26 Jun 2022 08:43:40 -0400) it happened legg
legg@nospam.magma.ca> wrote in <9jjgbhhjkqbqjr4krsm1g9dco3oc495k2d@4ax.com>:

On Sun, 26 Jun 2022 05:00:35 -0700 (PDT), Phil Allison
pallison49@gmail.com> wrote:

Jan Panteltje wrote:

=====================

In the UPS case you do not charge into an _empty_ capacitor, if the UPS functions right
then it is just the discharge difference from the last mains period (depends on wallwart load),
the peak current will be limited also by the resistance of the series diodes,
and by the Zi from the UPS etc..

**Yep.

Square wave charges for a longer time,

** Nonsense.

No charging pulses AT ALL.
It\'s fucking DC you fool.



..... Phil

They\'re talking about wallwarts loading the output of
a UPS inverter that generates a 120VAC output with either
a square or sine waveform.

Capacitive rectified input filters of the wallwarts\'
primary(SMPS), or capacitive rectified output filters
of the wallwart\'s (linear) secondaries will produce a
different 120VAC current crest factor, depending on
whether they are fed by a square or sine wave.

If a square wave has it\'s simplest form (+-120V ~180degree,
then crest factor is low, but the capacitive rectified
output voltage will be only 70% of that produced by a 120V
sine source.

If the square vave is tailored to produce a more similar
output (peak to RMS ratio), with higher voltage at a
reduced duty cycle, then crest factor of rectified current
will increase, and can easily exceed that of the sinusoidal
standard input. Input current will look more like an RC
charge/discharge, than a haversine charge/RC discharge.

RL

Here the waveform of my cheap UPS loaded with a normal 25 W lightbulb:
http://www.panteltje.com/pub/APC_UPS_ES700_waveform_25W_edison_bulb_load_IMG_0270.JPG

measured a while back when it was new,
230V AC 50Hz Europe, cannot read the Vpp from the picture
but 230 * sqrt(2) = 325, *2 = 650 Vpp
this looks like 5 to 6 divisions maybe around 500 to 600 Vpp (not sure).
Waveform is interesting

That\'s the modified square wave. It will produce quite peaky
current waveforms in a capacitive rectified filter.

But, as you\'ve said, if it works, it works. The OP was trying to
predict performance, based on insufficient information.

RL

I can imagine a fast rise heating up the first cap in a non-PFC wart.
Their usual failure mode is a bad cap. Might stress the usual series
resistor too.

A temperature comparison wouldn\'t be difficult.

(I\'m designing power supplies lately, and cap esr heating is part of
the puzzle.)

 

[Jan Panteltje]

On a sunny day (Sun, 26 Jun 2022 10:27:49 -0400) it happened legg
<legg@nospam.magma.ca> wrote in <asqgbh545t97hl10p0mlm2j66li2pe42tq@4ax.com>:

On Sun, 26 Jun 2022 13:29:08 GMT, Jan Panteltje
pNaonStpealmtje@yahoo.com> wrote:
Here the waveform of my cheap UPS loaded with a normal 25 W lightbulb:
http://www.panteltje.com/pub/APC_UPS_ES700_waveform_25W_edison_bulb_load_IMG_0270.JPG

measured a while back when it was new,
230V AC 50Hz Europe, cannot read the Vpp from the picture
but 230 * sqrt(2) = 325, *2 = 650 Vpp
this looks like 5 to 6 divisions maybe around 500 to 600 Vpp (not sure).
Waveform is interesting

That\'s the modified square wave. It will produce quite peaky
current waveforms in a capacitive rectified filter.

But, as you\'ve said, if it works, it works. The OP was trying to
predict performance, based on insufficient information.

Yes, and most of the wallwarts I have have a big input voltage range
like 110 to 230 V AC.

That gives the UPC some time to come in in case of 230V

 

[server]

On Thu, 30 Jun 2022 14:52:03 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

jlarkin@highlandsniptechnology.com wrote:
On Thu, 30 Jun 2022 09:25:24 -0400, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

Clifford Heath wrote:
On 30/6/22 05:38, Phil Hobbs wrote:
Even in an inviscid, incompressible fluid, the equations aren\'t all
that simple.  Forced-air cooling of macroscopic systems runs at some
huge and highly variable Reynolds number, depending on where you are.

Pretty sure that Reynolds number cannot be defined for an inviscid
liquid. But yeah, turbulent flows are difficult however you look at them.

My point exactly.


Sure. But is my plate 0.2 k/w, or is it 20 k/w?


A zero-order approximation would be to assume that the boundary layer is
~5 mm thick, and the plate behaves like still air of that thickness
connected to an infinite heat sink at the outlet temperature.

You can compute the outlet temperature using the mass flow rate, heat
capacity of air, inlet temperature, and power dissipation.

I\'d expect things to improve faster than linearly with flow rate,
because the boundary layer should thin down as well as the outlet
temperature falling.

Cheers

Phil Hobbs

On that basis, with 200 ft/min flowing across both sides of my 4\"
square plate, I get just around 1 K/W. Sounds optimistic, but I\'ll try
it.

 

[Phil Allison]

legg wrote:
===============
Phil Allison

Square wave charges for a longer time,

** Nonsense.

No charging pulses AT ALL.
It\'s fucking DC you fool.



If a square wave has it\'s simplest form (+-120V ~180degree,
then crest factor is low, but the capacitive rectified
output voltage will be only 70% of that produced by a 120V
sine source.

** The man said \" square wave \" - over and over.

If the square vave is tailored to produce a more similar
output (peak to RMS ratio), with higher voltage at a
reduced duty cycle,

** Not a *square wave* any more.




...... Phil

 

[legg]

On Sat, 25 Jun 2022 07:32:27 -0400, legg <legg@nospam.magma.ca> wrote:

On Sat, 25 Jun 2022 02:10:59 -0000 (UTC), bob prohaska
bp@www.zefox.net> wrote:

I\'m setting up a UPS for my computer/comms equipment using an
inverter/charger and battery from Amazon. The equipment draw
is only about 40 watts measured with a Kill-A-Watt, but all
the associated wallwarts use capacitive-input switching power
supplies. That means they only draw current at line peaks.

My seat-of-the-pants guess is that the duty cycle is around 10%,
meaning that the average 40 watts is really 400 watts 10% of the time.
That\'s well within the continuous power rating of the inverter, which
is 800 watts, so it\'s likely the setup will work as it is.

The question is: Can the peak load be made closer to the average
load by putting an inductor in the AC line feeding the wallwarts?

If anybody\'s been through this exercise I\'d be grateful for guidance.

Thanks for reading,

bob prohaska



I did some passive correction for off-the-shelf 60Hz linears in
the 80s. Best effects achieved using a saturable choke and
quasi-resonant capacitor, over a limited range of power levels
for any specific installation.

The parts are generally impractical for a hobbyist to get
ahold of, though restacking laminations from unvarnished scrap
is possible. Requires good VP Impregnation to silence the
final iteration.

The actual current phase angle shifted from leading to lagging
over the useful range. Output voltage into the 60Hz capacitive
load was flat-topped, affecting the low-line voltage performance.
The choke/cap combination supported the output difference
during line current reversal.

It\'s no good guessing what the current waveshape is; you\'ve
got to measure it / scope it. Line current transformers are
pretty cheap these days, often included in <$10 wattmeters
from off-shore sources. A scope is useful, but more expensive.

A lot of modern wall-warts are actually PFC compliant, through
the use of dedicated low power integrated controllers. These
employ valley-fill or critical-conduction (FM) off-line switchers
economically, at power levels as low as 5W.

Don\'t guess. Measure. Read specs of devices involved.

Don\'t go overboard. Your UPS output may be more tolerant of peak
loads than you assume, and your loads may be less peaky, simply
due to industry commodity trends and available parts.

RL

Some work on different rectifier and filter/pre-filter circuitry
was published by Richard Redl and Laszlo Balogh ~1995.
Some notes I made in the 80s, on the simplest LC configuration
are also included in this zip file.

In the latter, the effect of series choke saturation at above-
nominal loads is illustrated.

http://ve3ute.ca/query/passive_power_factor_diag.zip

When standards docs start talking about total harmonic distortion
and specs include power factors >95%, you can pretty much rule out
passive approaches. They can be simple, reliable, quiet and
effective in reducing generator and interconnection losses.
.. . . which is the OP\'s actual concern.

RL

 

[Fred Bloggs]

On Friday, June 24, 2022 at 10:11:06 PM UTC-4, bob prohaska wrote:

I\'m setting up a UPS for my computer/comms equipment using an
inverter/charger and battery from Amazon. The equipment draw
is only about 40 watts measured with a Kill-A-Watt, but all
the associated wallwarts use capacitive-input switching power
supplies. That means they only draw current at line peaks.

My seat-of-the-pants guess is that the duty cycle is around 10%,
meaning that the average 40 watts is really 400 watts 10% of the time.
That\'s well within the continuous power rating of the inverter, which
is 800 watts, so it\'s likely the setup will work as it is.

The question is: Can the peak load be made closer to the average
load by putting an inductor in the AC line feeding the wallwarts?

If anybody\'s been through this exercise I\'d be grateful for guidance.

Thanks for reading,

Look at the plug-in output voltage inverter-fed versus line-fed. If no difference, then no issue. Look at the inverter RMS output with and without a bunch of plug-ins. If no difference then no issue.

bob prohaska

 

[Fred Bloggs]

On Saturday, June 25, 2022 at 1:24:40 AM UTC-4, John Doe wrote:

Jan Panteltje <pNaonSt...@yahoo.com> wrote:
bob prohaska wrote:

I\'m setting up a UPS for my computer/comms equipment using an
inverter/charger and battery from Amazon. The equipment draw is only
about 40 watts measured with a Kill-A-Watt, but all the associated
wallwarts use capacitive-input switching power supplies. That means
they only draw current at line peaks.

My seat-of-the-pants guess is that the duty cycle is around 10%, meaning
that the average 40 watts is really 400 watts 10% of the time. That\'s
well within the continuous power rating of the inverter, which is 800
watts, so it\'s likely the setup will work as it is.

The question is: Can the peak load be made closer to the average load by
putting an inductor in the AC line feeding the wallwarts?

If anybody\'s been through this exercise I\'d be grateful for guidance.
Interesting question, my cheap UPS seems to put out a square wave I
wondered if the flat tops are actually not better for the wall warts as
the charging part is longer than with a sine wave top... Been working
now fine for a year or so with this thing, comes in almost every day
these days with mains company fiddling,.. flashing light bulbs sometimes
here too. To backup for longer times I have a pure sine wave 2 kW
converter and a 250 Ah lifepo4 battery.. So I can keep watching sat TV
or even cook food. More than 10 wallwarts on that UPS now, some
Raspberry Pi, some USB hubs, some cameras., also security recorder,
monitors... .. audio amp... 4 TB harddisks... I would personally not
bother with a a series inductor...
For a personal computer only... I use a Tripp-Lite LC1200. No battery at
all. I don\'t recall the last time we had a power failure that lasted more
than an moment. But there has been flickering. The line conditioner works
great for momentary outages, no messing with a battery.

Of course that doesn\'t suit everybody.

They just lifted the same technology used in inverter generators. If it coasts through what you call a momentary outage then it wasn\'t an outage. The price is pretty good but then again 1200 Watt is not really that much. Are you mining bitcoins or something? What in the world kind of computer setup requires 1200W these days...

 

[John Doe]

By \"momentary outage\", I mean momentary loss of power. Like a dip, a drop,
a sag, whatever you want to call it.

I have a 1200 W line conditioner because for overkill. I guess it might
help increase the momentary outage protection. Other stuff flickers, but
not stuff connected to the line conditioner (like my PC or its monitor).
Even if it doesn\'t help, it doesn\'t hurt.

It\'s worked great without having to mess with a battery. When the power
does go off for more than a second, the PC stays off instead of Windows
rebooting. But that hasn\'t happened in years.

That line conditioner with its clicking sound and LEDs also keeps one
aware of room/house/neighborhood voltage. I like being aware of stuff.



Fred Bloggs <bloggs.fredbloggs.fred@gmail.com> wrote:

On Saturday, June 25, 2022 at 1:24:40 AM UTC-4, John Doe wrote:
Jan Panteltje <pNaonSt...@yahoo.com> wrote:
bob prohaska wrote:

I\'m setting up a UPS for my computer/comms equipment using an
inverter/charger and battery from Amazon. The equipment draw is only
about 40 watts measured with a Kill-A-Watt, but all the associated
wallwarts use capacitive-input switching power supplies. That means
they only draw current at line peaks.

My seat-of-the-pants guess is that the duty cycle is around 10%, meanin
g
that the average 40 watts is really 400 watts 10% of the time. That\'s

well within the continuous power rating of the inverter, which is 800

watts, so it\'s likely the setup will work as it is.

The question is: Can the peak load be made closer to the average load b
y
putting an inductor in the AC line feeding the wallwarts?

If anybody\'s been through this exercise I\'d be grateful for guidance.
Interesting question, my cheap UPS seems to put out a square wave I
wondered if the flat tops are actually not better for the wall warts as

the charging part is longer than with a sine wave top... Been working

now fine for a year or so with this thing, comes in almost every day
these days with mains company fiddling,.. flashing light bulbs sometime
s
here too. To backup for longer times I have a pure sine wave 2 kW
converter and a 250 Ah lifepo4 battery.. So I can keep watching sat TV

or even cook food. More than 10 wallwarts on that UPS now, some
Raspberry Pi, some USB hubs, some cameras., also security recorder,
monitors... .. audio amp... 4 TB harddisks... I would personally not
bother with a a series inductor...
For a personal computer only... I use a Tripp-Lite LC1200. No battery at

all. I don\'t recall the last time we had a power failure that lasted more

than an moment. But there has been flickering. The line conditioner works

great for momentary outages, no messing with a battery.

Of course that doesn\'t suit everybody.

They just lifted the same technology used in inverter generators. If it coasts through what you call a momentary outage then it wasn\'t an outage. The price is pretty good but then again 1200 Watt is not really that much. Are you mining bitcoins or something? What in the world kind of computer setup requires 1200W these days...

 

[Jan Panteltje]

On a sunny day (Mon, 27 Jun 2022 09:42:08 -0400) it happened legg
<legg@nospam.magma.ca> wrote in <mlbjbhp55bpidiekuu6pjjsk607695aths@4ax.com>:

On Sat, 25 Jun 2022 07:32:27 -0400, legg <legg@nospam.magma.ca> wrote:

On Sat, 25 Jun 2022 02:10:59 -0000 (UTC), bob prohaska
bp@www.zefox.net> wrote:

I\'m setting up a UPS for my computer/comms equipment using an
inverter/charger and battery from Amazon. The equipment draw
is only about 40 watts measured with a Kill-A-Watt, but all
the associated wallwarts use capacitive-input switching power
supplies. That means they only draw current at line peaks.

My seat-of-the-pants guess is that the duty cycle is around 10%,
meaning that the average 40 watts is really 400 watts 10% of the time.
That\'s well within the continuous power rating of the inverter, which
is 800 watts, so it\'s likely the setup will work as it is.

The question is: Can the peak load be made closer to the average
load by putting an inductor in the AC line feeding the wallwarts?

If anybody\'s been through this exercise I\'d be grateful for guidance.

Thanks for reading,

bob prohaska



I did some passive correction for off-the-shelf 60Hz linears in
the 80s. Best effects achieved using a saturable choke and
quasi-resonant capacitor, over a limited range of power levels
for any specific installation.

The parts are generally impractical for a hobbyist to get
ahold of, though restacking laminations from unvarnished scrap
is possible. Requires good VP Impregnation to silence the
final iteration.

The actual current phase angle shifted from leading to lagging
over the useful range. Output voltage into the 60Hz capacitive
load was flat-topped, affecting the low-line voltage performance.
The choke/cap combination supported the output difference
during line current reversal.

It\'s no good guessing what the current waveshape is; you\'ve
got to measure it / scope it. Line current transformers are
pretty cheap these days, often included in <$10 wattmeters
from off-shore sources. A scope is useful, but more expensive.

A lot of modern wall-warts are actually PFC compliant, through
the use of dedicated low power integrated controllers. These
employ valley-fill or critical-conduction (FM) off-line switchers
economically, at power levels as low as 5W.

Don\'t guess. Measure. Read specs of devices involved.

Don\'t go overboard. Your UPS output may be more tolerant of peak
loads than you assume, and your loads may be less peaky, simply
due to industry commodity trends and available parts.

RL

Some work on different rectifier and filter/pre-filter circuitry
was published by Richard Redl and Laszlo Balogh ~1995.
Some notes I made in the 80s, on the simplest LC configuration
are also included in this zip file.

In the latter, the effect of series choke saturation at above-
nominal loads is illustrated.

http://ve3ute.ca/query/passive_power_factor_diag.zip

When standards docs start talking about total harmonic distortion
and specs include power factors >95%, you can pretty much rule out
passive approaches. They can be simple, reliable, quiet and
effective in reducing generator and interconnection losses.
. . . which is the OP\'s actual concern.

RL

I did some back of the envelope calculation on (well actually I used wcalc)
how much the input elctrolytic in a 12 W (12 V 1 A) wallwart discharges
between mains periods with a bridge (so 10 mS here in 50 Hz land)
IIRC that was about 57 volt ripple! on that tiny cap (usually 4.7 uF / 400 V type).
No wonder all those electrolytics fail (have repaired many wallwarts here,
BTW I also use floorwarts:
http://panteltje.com/pub/floor_warts_IXIMG_0790.JPG
all that on same UPS too.

Primary cap discharge current between mains peaks:
Given secundary 12 V 1 A and 350 V on primary cap 12 / 350 = 34 mA,
but taking into account efficiency say 50 mA then if cap is 5 uF and t = 10 mS
As Q = C.U = i.t -> U = i.t / C
= (50E-3 * 10E-3) / 5E-6 = 100 V ripple!
50 V ripple for a 10 uF...

4.7 uF 400 V seems to be the normal in those small wallwarts (5 V 1 A), so I have a bunch of those,
and also some big ones for the secondary caps, those often get puffed too.

Maybe I goofed the math, but next time one goes I will scope that ripple
Normally you can visually spot those bad caps because they will all be swollen.

Anybody measured the ripple?