PC power supply question

[Steve Pope]

Does anyone have an opinion on the following:

Suppose a power supply for a desktop PC has four 12 VDC outputs,
each rated at 20 amps, with an overall rating of 800 watts.

Can one safely gang together these four outputs to create
an ~66 amp power source (assuming sufficient connector ratings
and wire gauges)?

(Obiously the answer to this will depend on the exact model
of the power supply and its ratings, so I am just looking for
a general answer here.)

Thanks

Steve

[sms]

Post by Steve Pope
Suppose a power supply for a desktop PC has four 12 VDC outputs,
each rated at 20 amps, with an overall rating of 800 watts.
Can one safely gang together these four outputs to create
an ~66 amp power source (assuming sufficient connector ratings
and wire gauges)?

No.

[Roy]

Post by Steve Pope
Suppose a power supply for a desktop PC has four 12 VDC outputs,
each rated at 20 amps, with an overall rating of 800 watts.
Can one safely gang together these four outputs to create
an ~66 amp power source (assuming sufficient connector ratings
and wire gauges)?
(Obiously the answer to this will depend on the exact model
of the power supply and its ratings, so I am just looking for
a general answer here.)
Thanks
Steve

You can't simply tie them together. There are ways to do it but it
would require non-trivial circuitry.

[Julian Macassey]

On Thu, 4 Jun 2015 05:37:08 +0000 (UTC), Steve Pope

Post by Steve Pope
Suppose a power supply for a desktop PC has four 12 VDC outputs,
each rated at 20 amps, with an overall rating of 800 watts.
Can one safely gang together these four outputs to create
an ~66 amp power source (assuming sufficient connector ratings
and wire gauges)?

I do know that with PC switching supplies you can add the
outputs in series to get a higher voltage. I'm not sure about
adding them in parelell. I would assume you have to make sure
they share and balance the load.

[Jeff Liebermann]

Post by Steve Pope
Suppose a power supply for a desktop PC has four 12 VDC outputs,
each rated at 20 amps, with an overall rating of 800 watts.
Can one safely gang together these four outputs to create
an ~66 amp power source (assuming sufficient connector ratings
and wire gauges)?

No, or rather not easily. The problem is that each power supply has
its own built in voltage regulation system. When you parallel the
outputs, you are putting the regulators in parallel. Since they
cannot be identically set, they will fight each other for control. I
con't predict what will happen, but it probably won't be anything
useful or desireable.

You could isolate the outputs with four Shottky diodes, one for each
power supply. They would need to be power diodes and properly heat
sinked. You would also need to carefully adjust each power supply so
that each provides its share of the total current. That's not easy
with commidity ATX power supplies. If you measure the current from
each power supply, I suspect the currents will be quite different,
especially if the power supplies are not identical. There are also
some response time issues caused by the diodes.

Incidentally, don't believe the nameplate ratings on most ATX power
supplies. Your 800 watt rated power supply will probably not be able
to produce 800 watts and certainly not with only a single tiny fan.
I've tested various lesser (about 350-350 watt) power supplies using a
resistor load rack and a bucket of water and found all of them lacking
near their maximum output. A few couldn't even produce 1/2 the
nameplate rating.

I suggest you look at industrial power supplies:
<http://www.mpja.com/12-Volt-Power-Supply/products/537/>
or possibly using an automobile battery for the 12V.

[Steve Pope]

Thanks for all the replies.

Post by Jeff Liebermann

Post by Steve Pope
Suppose a power supply for a desktop PC has four 12 VDC outputs,
each rated at 20 amps, with an overall rating of 800 watts.
Can one safely gang together these four outputs to create
an ~66 amp power source (assuming sufficient connector ratings
and wire gauges)?

No, or rather not easily. The problem is that each power supply has
its own built in voltage regulation system. When you parallel the
outputs, you are putting the regulators in parallel. Since they
cannot be identically set, they will fight each other for control. I
con't predict what will happen, but it probably won't be anything
useful or desireable.

Yes, that was my suspicion.

Post by Jeff Liebermann
You could isolate the outputs with four Shottky diodes, one for each
power supply. They would need to be power diodes and properly heat
sinked. You would also need to carefully adjust each power supply so
that each provides its share of the total current. That's not easy
with commidity ATX power supplies. If you measure the current from
each power supply, I suspect the currents will be quite different,
especially if the power supplies are not identical. There are also
some response time issues caused by the diodes.
Incidentally, don't believe the nameplate ratings on most ATX power
supplies. Your 800 watt rated power supply will probably not be able
to produce 800 watts and certainly not with only a single tiny fan.
I've tested various lesser (about 350-350 watt) power supplies using a
resistor load rack and a bucket of water and found all of them lacking
near their maximum output. A few couldn't even produce 1/2 the
nameplate rating.
<http://www.mpja.com/12-Volt-Power-Supply/products/537/>
or possibly using an automobile battery for the 12V.

My goal here is to create an inexpensive supply/inverter combo
that will convert 240 VAC, 50 Hz to 120 VAC, 60 Hz, with
perhaps 600 watt capacity.

You'd think that would be an easy problem to solve, but not
at low cost.

For the inverter, the 12V input models are the most inexpensive
due to their being high volume since people run these of
car batteries (or marine etc.) Other things being equal,
I'd prefer 24V or 48V input but those seem to cost significantly
more.

Whereas for the power supplies, the PC power supplies seem
to be the least expensive.

Julian states the four 12V outputs might be wired in series
so maybe finding a cheap-enough 48V-input inverter is
a solution.

For paralleling the outputs, one idea I had for isolating them
is to insert 0.027 ohms of series resistance in each output.
At full power the resistor would dissapate under 10 watts,
and there would be up to 0.5V of voltage drop. The cost of
film resistors (Panasonic) that could do this is $3.60 (in
low volumes) but there would be non trivial packaging design/cost
(either a board or a wire harness). One may also want a bleed
resistor in there so that there is always some drop across the
series resistors.

I had not thought of the Shottkey diode approach, that seems
reasonable also.

The approach of using a car battery.(and trickle charger) is
would do just fine for low-duty-cycle usage.

It seems the price of 12V DC supplies jumps up above 300W or so.

I'll keep looking, thanks everyone.


Steve

[Jeff Liebermann]

Post by Steve Pope
My goal here is to create an inexpensive supply/inverter combo
that will convert 240 VAC, 50 Hz to 120 VAC, 60 Hz, with
perhaps 600 watt capacity.

Easy. 240VAC motor driving a 120VAC generator (or alternator). Throw
in a flywheel for regulation.

One phase, two phase, or 3 phase? If 3 phase, wye or tee?
Got a target overall efficiency specification?
Will you need power factor correction? That can wreck the efficiency.
Duz it have to be in two parts with DC in between or can it be just
one big power supply?
Sine wave, modified sine wave, or ugly harmonic infested mess?
Are you building one, or designing something for production? The
choice and availability of components will be different.

You might do better with your question in sci.electronics.design.

Note that there are already commercial products that do what you want:
<http://www.gohz.com/frequency-converter>
<http://www.frequencyconverter.net>
<http://www.pcti.com/products/frequency-converters/>
More...
<https://www.google.com/#q=50+to+60hz+power+converter>

[Roy]

Post by Steve Pope
...
My goal here is to create an inexpensive supply/inverter combo
that will convert 240 VAC, 50 Hz to 120 VAC, 60 Hz, with
perhaps 600 watt capacity.
You'd think that would be an easy problem to solve, but not
at low cost.
For the inverter, the 12V input models are the most inexpensive
due to their being high volume since people run these of
car batteries (or marine etc.) Other things being equal,
I'd prefer 24V or 48V input but those seem to cost significantly
more.
Whereas for the power supplies, the PC power supplies seem
to be the least expensive.
Julian states the four 12V outputs might be wired in series
so maybe finding a cheap-enough 48V-input inverter is
a solution.
For paralleling the outputs, one idea I had for isolating them
is to insert 0.027 ohms of series resistance in each output.
At full power the resistor would dissapate under 10 watts,
and there would be up to 0.5V of voltage drop. The cost of
film resistors (Panasonic) that could do this is $3.60 (in
low volumes) but there would be non trivial packaging design/cost
(either a board or a wire harness). One may also want a bleed
resistor in there so that there is always some drop across the
series resistors.
I had not thought of the Shottkey diode approach, that seems
reasonable also.
The approach of using a car battery.(and trickle charger) is
would do just fine for low-duty-cycle usage.
It seems the price of 12V DC supplies jumps up above 300W or so.
I'll keep looking, thanks everyone.
Steve

I think I would look at a straight transformer approach. Unless motors
are involved, the 50 or 60 Hz probably won't matter. With
globalization, more and more equipment has the capability of running on
various voltages.

When I was working for a big company in the 80s, we received a shipment
of display terminals with the instructions in Spanish and marked
220/50Hz but with US power cords. We called the plant (our company made
them) and found out the difference was the power cords and the fuse (2A
vs 1A). A European customer had cancelled their order and the shipment
was redirected to us. A quick trip to Orchard Supply and we were in
business.

Roy

[Steve Pope]

Post by Roy
I think I would look at a straight transformer approach. Unless motors
are involved, the 50 or 60 Hz probably won't matter. With
globalization, more and more equipment has the capability of running on
various voltages.

This is true, however, the inquiry I am responding to
(from an American ex-pat in Europe) has found that some
devices are still damaged (in some cases burn out entirely)
when fed 50Hz, 120V.

They are now trying to protect $1000 worth of stuff from damage,
and if there were an OTS product (pure- or quasi-pure sine wave)
that does the job and was $300 or less then they would be all
set. But there does not seem to be a product in that price
range.

The 12V car battery / trickle charger / 12V inverter is off the
shelf and can be hooked together by the consumer and comes in
at somewhere between $100 and $150. But, it cannot run 24/7,
is inconveniently heavy, contains icky chemicals etc.

I am probably not actually building this thing. It is mostly
just an idle thought.

Steve

[Julian Macassey]

On Thu, 4 Jun 2015 18:22:22 +0000 (UTC), Steve Pope

Post by Steve Pope
This is true, however, the inquiry I am responding to
(from an American ex-pat in Europe) has found that some
devices are still damaged (in some cases burn out entirely)
when fed 50Hz, 120V.

The 50Hz makes a difference? When I lived in Europe and
used US and Japanese equipment meant for 60 Hz (Yes I know Japan
has 50/60 Hz and 100V), the diffeernce was the transformers ran a
little warm. Stuffing 110 V 50Hz into a switching PSU shouldn't
matter.

Of course, you don't tell us exactly what this piece of
gear is. But even in the old days, pricey test gear etc. ran
fine, but sometimes you had to swap whole PSUs or just the
transformer.

When I was a pimply faced youth, the guy down the street
was the radio geek for the US embasssy. Much of his house,
especially kitchen appliances (Can't trust those Limey blenders),
ran on 110V 50 Hz. His house was the first time I saw an electric
frying pan, all the rage in the US at the time.

[Steve Pope]

Post by Julian Macassey

Post by Steve Pope
This is true, however, the inquiry I am responding to
(from an American ex-pat in Europe) has found that some
devices are still damaged (in some cases burn out entirely)
when fed 50Hz, 120V.

The 50Hz makes a difference? When I lived in Europe and
used US and Japanese equipment meant for 60 Hz (Yes I know Japan
has 50/60 Hz and 100V), the diffeernce was the transformers ran a
little warm. Stuffing 110 V 50Hz into a switching PSU shouldn't
matter.
Of course, you don't tell us exactly what this piece of
gear is.

I do not know the entire list but it includes "smart" kitchen
appliances and "smart" personal care items (hair tools, shavers, etc.)
that include some combination of heating elements and/or
electromechanics and electronics, the latter being the component
that generally fails.

Pure electronic devices do not fail and are often rated for
50 Hz anyway.

The way some things are designed these days is often sketch.
For example I once turned everything off in the house that
I thought should be drawing current, and there was still about
a 3 watt drain showing on my "smart meter". I traced this down to
a Krups coffee grinder, that includes a primitive electronic timer,
apparently drawing current when not in use.

More importantly, I have noticed that when using say an electric drill
on the same circuit as the (supposedly turned off) coffee grinder,
the latter's motor would randomly pulse every so many seconds.
I suspect the timer circuitry (which controls something like
an SCR to the motor) is designed and powered in some really cheap
manner, such that it not only draws quiescent current, it is sensitive
to line conditions.

Given this style of ... design integrity, it is more than possible
that similarly-conceived devices might be sensitive to 50 Hz
when they'e expecting 60 Hz.


Steve

[Julian Macassey]

On Thu, 4 Jun 2015 19:16:48 +0000 (UTC), Steve Pope

Post by Steve Pope
I do not know the entire list but it includes "smart" kitchen
appliances and "smart" personal care items (hair tools, shavers, etc.)
that include some combination of heating elements and/or
electromechanics and electronics, the latter being the component
that generally fails.

Regular hair dryers sold in the US for 110V use will work
in EU using just a diode to chop the AC wave in half. I know this
because I have done that for Merkins visiting Europe who were
shocked and amazed that they didn't have 110V in Europe and they
had funny plugs too. I have noticed that many hair dryers now
have a 110/220 switch.

Of course fancy gear like laptops tend to have switching
PSUs that work on pretty much anything that might be a sine wabe
from abouut 85V tp 260V.

But, electronics says DC and usually below 24V. So I
still fail to see the problem.

As for electric shavers, my dad's Philishave (Norelco)
had a 110/220 switch in the 1950s.

Post by Steve Pope
Pure electronic devices do not fail and are often rated for
50 Hz anyway.

As I note, pretty much everything, except for sybchronous
motors (electric wall clocks f. ex), isn't going to be care about
the Freq.

I can say though the ONLY prob I have had with US gear in
the EU is a backup PSU that had so much ground leakage it tripped
a UK GFI. It did have a nice UL sticker though.

[Steve Pope]

Post by Julian Macassey
Regular hair dryers sold in the US for 110V use will work
in EU using just a diode to chop the AC wave in half. I know this
because I have done that for Merkins visiting Europe who were
shocked and amazed that they didn't have 110V in Europe and they
had funny plugs too. I have noticed that many hair dryers now
have a 110/220 switch.
Of course fancy gear like laptops tend to have switching
PSUs that work on pretty much anything that might be a sine wabe
from abouut 85V tp 260V.

Yes, the only potential issue is the part of the laptop cable
that goes from the wall plug to the power supply block. These
are sometimes not 220V rated. It rarely causes an issue I have seen
one smoke at the plug end (a Lenovo netbook).

(But that is not the problem I am trying to solve.)

Post by Julian Macassey
But, electronics says DC and usually below 24V. So I
still fail to see the problem.
I can say though the ONLY prob I have had with US gear in
the EU is a backup PSU that had so much ground leakage it tripped
a UK GFI. It did have a nice UL sticker though.

The problems with 120V/50 Hz are uncommon but they definitely exist, given
a large enough number of users. (There are communities of thousands of
expats discussing these things, and their experiences/concerns
are real.)

Steve

[Julian Macassey]

On Thu, 4 Jun 2015 21:46:09 +0000 (UTC), Steve Pope

Post by Steve Pope
The problems with 120V/50 Hz are uncommon but they definitely exist, given
a large enough number of users. (There are communities of thousands of
expats discussing these things, and their experiences/concerns
are real.)

Any chance of specifics?

1. What communities?

2. Where are the communities?

3. What equipment exactly has the problem?

4.How do the problems manifest themselves?

What needs to be explained is what about the 50/60 Hz
difference is the problem?

[Steve Pope]

Post by Julian Macassey
On Thu, 4 Jun 2015 21:46:09 +0000 (UTC), Steve Pope

Post by Steve Pope
The problems with 120V/50 Hz are uncommon but they definitely exist, given
a large enough number of users. (There are communities of thousands of
expats discussing these things, and their experiences/concerns
are real.)

Any chance of specifics?
1. What communities?
2. Where are the communities?

Expat communities in southern Italy. Actually they are a blend
of expats and US military and contractors.

There is a chance the issues are specific to southern Italy where
the power line quality may be less stable than is typical for EU.
(I definitely encountered a lot of funky wiring when I lived
there some years back.)

Post by Julian Macassey
3. What equipment exactly has the problem?

Flat iron; curling iron; I will have to dredge up more specifics.

Post by Julian Macassey
4.How do the problems manifest themselves?

The typical description is a slowly increasing glitchiness ultimately
leading to

Post by Julian Macassey
What needs to be explained is what about the 50/60 Hz
difference is the problem?

I don't have an exact theory on this, just that simply using a
transformer does not seem to be enough. It could be as simple
as overall heating of a part with no design margin, perhaps compounded
with being in an area with quite hot mid-year weather.

Nor do I believe it's been scientifically established there
*is* a problem; just that there is a belief there is a problem.

Steve

[Julian Macassey]

On Fri, 5 Jun 2015 04:58:13 +0000 (UTC), Steve Pope

Post by Steve Pope

Post by Julian Macassey
On Thu, 4 Jun 2015 21:46:09 +0000 (UTC), Steve Pope

Post by Steve Pope
The problems with 120V/50 Hz are uncommon but they definitely exist, given
a large enough number of users. (There are communities of thousands of
expats discussing these things, and their experiences/concerns
are real.)

Any chance of specifics?
1. What communities?
2. Where are the communities?

Expat communities in southern Italy. Actually they are a blend
of expats and US military and contractors.
There is a chance the issues are specific to southern Italy where
the power line quality may be less stable than is typical for EU.
(I definitely encountered a lot of funky wiring when I lived
there some years back.)

Post by Julian Macassey
3. What equipment exactly has the problem?

Flat iron; curling iron; I will have to dredge up more specifics.

There is pretty much not much to go wrong with a curling
iron, it is is a resistive device, and the same with flat irons.

Which also begs the question. They do sell these is
Italy, you can buy them locally. A much cheaper and easier
solution than using a transformer. Why don't they do that?

Post by Steve Pope

Post by Julian Macassey
4.How do the problems manifest themselves?

The typical description is a slowly increasing glitchiness ultimately
leading to

Would it be different in the US? Could it be shitty
Wal*Mart quality gear. I do continuetp note a lack of specifics
"Increasing glitchiness", is up there with "poops out". Not a
symptom or ailment.

Post by Steve Pope

Post by Julian Macassey
What needs to be explained is what about the 50/60 Hz
difference is the problem?

I don't have an exact theory on this, just that simply using a
transformer does not seem to be enough. It could be as simple
as overall heating of a part with no design margin, perhaps compounded
with being in an area with quite hot mid-year weather.

If they were burning out, that would be a complete
failure not increasing glitchiness. As for hot weather, that
happens in the US too.

Post by Steve Pope
Nor do I believe it's been scientifically established there
*is* a problem; just that there is a belief there is a problem.

If they can't describe the problem, are they guessing
it's the Hertz?

[Steve Pope]

Post by Julian Macassey
On Fri, 5 Jun 2015 04:58:13 +0000 (UTC), Steve Pope

Post by Steve Pope

Post by Julian Macassey
3. What equipment exactly has the problem?

Flat iron; curling iron; I will have to dredge up more specifics.

There is pretty much not much to go wrong with a curling
iron, it is is a resistive device, and the same with flat irons.
Which also begs the question. They do sell these is
Italy, you can buy them locally. A much cheaper and easier
solution than using a transformer. Why don't they do that?

Well, they do. I think we're talking past each other, in the
sense that while many users will use a tranformer, many
others will buy an Italian unit, and these are valid solutions
for the majority of cases, I am looking for a solution
for the (hypothesized) edge cases where it appears the 50 Hz is
creating a specific problem for the north American units.

I'm not asserting that these edge cases have any particular
prevalance -- the data is too noisy for that, and the prevalence may
even be zero, and the persons involved are seeing random failures.

But, I'm interested if there's a better solution for these particular
cases, if they exist. (Or, cheaper than the full-fledged frequency
converters referenced by Jeff, which seem to start at around $1000
for the power ranges of interest.)



Steve

[sms]

Post by Steve Pope
But, I'm interested if there's a better solution for these particular
cases, if they exist. (Or, cheaper than the full-fledged frequency
converters referenced by Jeff, which seem to start at around $1000
for the power ranges of interest.)

An AC-DC-AC converter is a valid alternative to a motor-generator pair.
Full fledged frequency converters that are not mechanically based do
essentially what the commercial units do. The PC power supplies are very
efficient high-frequency switchers so the magnetic components can be
small. Even without frequency conversion it'd be a more compact solution
than a large low-frequency transformer.

It seems that every time someone posts a legitimate question, someone
has to question the motives. Obviously whoever needed this type of
conversion was not going to do it for a curling iron or flat iron, they
had a specific appliance in mind that actually required 50 Hz.

I suspect the reason the people I knew brought their Miele appliances
with them was because the company paid all their moving expenses but had
no provision in place to buy them new furniture and appliances in lieu
of moving their existing possessions.

[sms]

On 6/4/2015 2:27 PM, Julian Macassey wrote:

<snip>

Post by Julian Macassey
As I note, pretty much everything, except for sybchronous
motors (electric wall clocks f. ex), isn't going to be care about
the Freq.

I knew some people from the UK that brought over their European
220V/50Hz washer and dryer with mechanical timers. They used a
transformer for the appliances (at least for the washer, not sure if the
dryer was gas or electric). The wash cycle times were 1/6 shorter
because the timer was 1/6 faster and the tub and drum were 1/6 faster.
They said that they didn't notice the difference in terms of results.
Maybe the shorter cycle times were made up for by the more vigorous
agitation. For the dryer the drum spun 1/6 faster but they could
compensate for the timer difference.

At the currents Steve Pope is talking about I suspect he needs to run
some large appliances with synchronous motors.

[David Kaye]

I knew some people from the UK that brought over their European 220V/50Hz
washer and dryer with mechanical timers.

I'm wondering why; shipping cost must have been a bitch.

They said that they didn't notice the difference in terms of results.

A 50Hz motor running on 60Hz will be fine; a 60Hz motor running on 50Hz will
run hotter, so if it's being used near the upper limit of its design specs
there would be a problem.

Also, I've noticed that there are a number of automatically switching ATX
power supplies out there -- no input slide switch! It baffled me at first,
but then looking up the supply online it appeared to be universal. Not sure
if I remember the company; it may have been that one that Radio Shack used
to sell.




---
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus

[Eli the Bearded]

Post by David Kaye

I knew some people from the UK that brought over their European 220V/50Hz
washer and dryer with mechanical timers.

I'm wondering why; shipping cost must have been a bitch.

You get a 20' or 40' container, and you fill it. The marginal cost of
any particular item is low, even something as large as a washer/dryer
set. Plus, if your employer is moving you, you might not even be the
person footing the transport bill. (But in that case, if you bought
new ones *that* might be out of pocket.)

Elijah
------
how many intercontinental moves have you seen?

[Julian Macassey]

Post by sms
<snip>

Post by Julian Macassey
As I note, pretty much everything, except for sybchronous
motors (electric wall clocks f. ex), isn't going to be care about
the Freq.

I knew some people from the UK that brought over their European
220V/50Hz washer and dryer with mechanical timers. They used a
transformer for the appliances (at least for the washer, not sure if the
dryer was gas or electric). The wash cycle times were 1/6 shorter
because the timer was 1/6 faster and the tub and drum were 1/6 faster.
They said that they didn't notice the difference in terms of results.
Maybe the shorter cycle times were made up for by the more vigorous
agitation. For the dryer the drum spun 1/6 faster but they could
compensate for the timer difference.
At the currents Steve Pope is talking about I suspect he needs to run
some large appliances with synchronous motors.

Yes, synchronous motors would be the problem. That being
said, moving large appliances across the Atlantic makes littlle
sense, both sdes of the Atlantic have large appliances.

Plus, big husky transformers to run major appliances are
not cheap.

Plus, some manuafctuers - Boscj, Miele etc. are on bot
sides and you could probably swap out the motors.

[Steve Pope]

Post by Julian Macassey
Yes, synchronous motors would be the problem. That being
said, moving large appliances across the Atlantic makes littlle
sense, both sdes of the Atlantic have large appliances.

Employer-paid moving expenses I suspect.

Post by Julian Macassey
Plus, big husky transformers to run major appliances are
not cheap.
Plus, some manuafctuers - Boscj, Miele etc. are on both
sides and you could probably swap out the motors.

Maybe; in a recent kitchen remodel we installed two Miele units
and one Liebherr; during the research phase there did not seem to be a
good concordance of product lines between the two sides of the Atlantic.

For one thing the standard appliance widths are not in inches, and so are
different.

(I'm very impressed with Miele quality BTW.)

Steve

[Julian Macassey]

On Fri, 5 Jun 2015 05:02:55 +0000 (UTC), Steve Pope

Post by Steve Pope

Post by Julian Macassey
Yes, synchronous motors would be the problem. That being
said, moving large appliances across the Atlantic makes littlle
sense, both sdes of the Atlantic have large appliances.

Employer-paid moving expenses I suspect.

If they had any smarts, they would leave the stuff in the
US and hit up the expenses at the other end. See below for
possible grief with large appliances etc. Then of course they
could be suffering from what I call "Base Blindness", and assume
everything has to be US specs. I came across US water heaters in
my travels abroad. Plumbing those suckers in must have been a
trial.

Post by Steve Pope

Post by Julian Macassey
Plus, some manuafctuers - Boscj, Miele etc. are on both
sides and you could probably swap out the motors.

Maybe; in a recent kitchen remodel we installed two Miele units
and one Liebherr; during the research phase there did not seem to be a
good concordance of product lines between the two sides of the Atlantic.

But, I would hazard a guess that motors etc. would swap
out. But as you note exterior dimensions, wiring etc. differ.

Post by Steve Pope
For one thing the standard appliance widths are not in inches, and so are
different.

The US is stuck on a measuring system created by English
Kings. Plus, there is a lack of standardisation, meaning
manufacturers all have their own standards. Fun, fun, fun.

Here's a nice Italian large appliance manufacturer.

http://www.indesit.co.uk/indesit/entryPoint.do

And Brit company making small kitchen appliances.

http://www.dualit.com/

I have a US version of their stick blender.

Post by Steve Pope
(I'm very impressed with Miele quality BTW.)

Yup, they make good stuff.

[Jeff Liebermann]

Post by Roy
I think I would look at a straight transformer approach. Unless motors
are involved, the 50 or 60 Hz probably won't matter. With
globalization, more and more equipment has the capability of running on
various voltages.

Good point. Since the customer will be supplying the xformer, all
that's needed is to specify one that is rated at 50/60 Hz and the
problem is solved as long as both the input and output are single
phase power.

[David Kaye]

Post by Jeff Liebermann
I've tested various lesser (about 350-350 watt) power supplies using a
resistor load rack and a bucket of water and found all of them lacking
near their maximum output. A few couldn't even produce 1/2 the
nameplate rating.

My impression that the power ratings are best-case peak power load, not
sustained load. Looking at the insides of a 350 watt supply it seemed to me
that it just doesn't have enough guts to handle 350.




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[Jeff Liebermann]

On Thu, 4 Jun 2015 16:59:00 -0700, "David Kaye"

Post by David Kaye

Post by Jeff Liebermann
I've tested various lesser (about 350-350 watt) power supplies using a
resistor load rack and a bucket of water and found all of them lacking
near their maximum output. A few couldn't even produce 1/2 the
nameplate rating.

My impression that the power ratings are best-case peak power load, not
sustained load. Looking at the insides of a 350 watt supply it seemed to me
that it just doesn't have enough guts to handle 350.

Yep. See:
<http://www.formfactors.org/developer%5Cspecs%5CPower_Supply_Design_Guide_Desktop_Platform_Rev_1_2.pdf>
Power delivery is specified all over the document, in various forms,
and for various power levels. However, I couldn't find anything that
clearly states that the numbers are for continuous duty. The best I
can do is note that there is no duty cycle, derating, or anything that
implies less than continuous duty.

On Pg 41, I found:
6.1 Temperature - RECOMMENDED
Operating ambient +10 °C to +50 °C (At full load, with a
maximum temperature rate of change of 5 °C/10 minutes, but
no more than 10 °C/hr.)
That's going to hard to do with any power supply unless it has a HUGE
fan. A typical 350 watt ATX power supply will probably run at 90%
efficiency, therefore dissipating 35 watts as heat. Assuming the 1hr
test is effectively continuous duty, that's:
10C / 35 watts = 0.29 C/W
which is about what I would expect from a small heat sink cooled with
an 80mm fan running optimistically at full blast at about 40cfm. By
the time we get to 600 watts, the specs are science fiction.

[sms]

Post by Steve Pope
Suppose a power supply for a desktop PC has four 12 VDC outputs,
each rated at 20 amps, with an overall rating of 800 watts.
Can one safely gang together these four outputs to create
an ~66 amp power source (assuming sufficient connector ratings
and wire gauges)?
(Obiously the answer to this will depend on the exact model
of the power supply and its ratings, so I am just looking for
a general answer here.)

Some PC supplies have a single +12V rail:

"Massive and dedicated +12V output

Smart Standard Series is equipped with a pure and powerful single +12V
rail to provide the best compatibility for your PC."

See <http://www.thermaltakeusa.com/products-model.aspx?id=C_00001977>

This is $44 at Fry's with the promo code until 6/6. The spec says 62A of
+12V.

They have one with 70A of +12
<http://www.thermaltakeusa.com/Power_Supply/Smart_Series_/Smart/C_00001972/SMART_M850W_US_/design.htm>

They have one with dual +12V outputs, but one of the two is 80A.
<http://www.thermaltakeusa.com/Power_Supply/Smart_Series_/Smart/C_00001973/SMART_M1000W_US_/design.htm>

[Steve Pope]

Post by sms
"Massive and dedicated +12V output
Smart Standard Series is equipped with a pure and powerful single +12V
rail to provide the best compatibility for your PC."
See <http://www.thermaltakeusa.com/products-model.aspx?id=C_00001977>
This is $44 at Fry's with the promo code until 6/6. The spec says 62A of
+12V.

Steven -- thanks!

Steve