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Generators and switch mode power supplies.

S

Sylvia Else

Jan 1, 1970
0
Given the parlous state of Australia's power systems, I've been
considering buying a standby generator. One marketing point of some of
the inverter based models is their suitability for 'sensitive
electronics' with computers given as an example. This appears to be
based on the fact that they'll provide a consistent sinewave output.

But given that computers invariably use switch-mode power supplies, are
they actually going to care what waveform they see - from square wave
thru 'modified sinewave' thru pure sinewave?

Sylvia.
 
T

TheM

Jan 1, 1970
0
Sylvia Else said:
Given the parlous state of Australia's power systems, I've been considering buying a standby generator. One marketing point of
some of the inverter based models is their suitability for 'sensitive electronics' with computers given as an example. This
appears to be based on the fact that they'll provide a consistent sinewave output.

But given that computers invariably use switch-mode power supplies, are they actually going to care what waveform they see - from
square wave thru 'modified sinewave' thru pure sinewave?

Sylvia.

Well, usually switcher has a full-wave rectifier and a smoothing cap
at the input. This means it probably works fine even with DC voltage.
The PC and similar stuff should be happy.

Stuff that runs through transformers may not like square wave.

You could run it through a good UPS (the kind that rectifies and re-generates
AC) to get good regulation and waveform.

M
 
Z

ZACK`

Jan 1, 1970
0
Sylvia Else said:
Given the parlous state of Australia's power systems, I've been
considering buying a standby generator. One marketing point of some of the
inverter based models is their suitability for 'sensitive electronics'
with computers given as an example. This appears to be based on the fact
that they'll provide a consistent sinewave output.

But given that computers invariably use switch-mode power supplies, are
they actually going to care what waveform they see - from square wave thru
'modified sinewave' thru pure sinewave?

Sylvia.

if you have store that sells the scorpian range
theres a new type of genset, thay are the
permanant magnet pure sinewave range, thay will run anything.

i have one of these its a 6.8kva model PM6500LX
thay have no electronics in them to go wrong
no brushes no caps no inverters.
 
Given the parlous state of Australia's power systems, I've been
considering buying a standby generator. One marketing point of some of
the inverter based models is their suitability for 'sensitive
electronics' with computers given as an example. This appears to be
based on the fact that they'll provide a consistent sinewave output.

But given that computers invariably use switch-mode power supplies, are
they actually going to care what waveform they see - from square wave
thru 'modified sinewave' thru pure sinewave?

Sylvia.

I fried a notebook power supply on a modified since wave inverter. I
won't run any electronics on those beasts again. However, I don't know
the mechanism of why the modified sine inverter fried the power
supply. Given how a switching supply works, I didn't consider feeding
a switcher with a cheap inverter to be a problem, but reality was
different. Well, it was only a $100 lesson. It the notebook got fried,
I think I would have been a little more POd. If I had to run
electronics on a generator, it would be with one of those inverter
generators.

The other advantage to the inverter generators is they worked on
making them quiet.

Incidentally, generators are pretty easy to get used. People buy them
for a particular lifestyle (say camping in the outback), then
circumstances change (a newborn in the family keeps them at home,
etc.).
 
P

Phil Allison

Jan 1, 1970
0
"Sylvia Else"
Given the parlous state of Australia's power systems, I've been
considering buying a standby generator. One marketing point of some of the
inverter based models is their suitability for 'sensitive electronics'
with computers given as an example.

** Pure marketing hype.

This appears to be based on the fact that they'll provide a consistent
sinewave output.


** All generators provide a reasonable sine wave.

But some do not have a steady or accurate frequency.

But given that computers invariably use switch-mode power supplies, are
they actually going to care what waveform they see - from square wave thru
'modified sinewave' thru pure sinewave?


** No *generator* ever puts out a square wave or modified square wave.

You are BARKING up the wrong tree BITCH.




...... Phil
 
   A few considerations:
1) Many inverters do NOT isolate; a relay drops out when the power
failes, and that turns on the inverter.
2) AFAIK there are NO sine wave inverters, the best are pseudo-sine wave
and even that waveform is not suitable to some equipment - which might
be damaged.
3) A PC could run off of (roughly) 240VDC, BUT a number of monitors need AC.
4) Then there are all of those accessories running from....wall warts;
more AC needed.
   Those last 2 items mentioned may be waveform sensitive...

You can get -48V supplies for PCs, rather than run of AC. I don't
think I ever saw a PC supply that did both AC and DC, but that would
be a nice product.

http://www.trcelectronics.com/48-volt-power-supply.shtml
is the first google hit.
 
S

Sylvia Else

Jan 1, 1970
0
Phil said:
"Sylvia Else"

** Pure marketing hype.




** All generators provide a reasonable sine wave.

Really? Well, I suppose it depends on your definition of "reasonable".
How about this one?

http://www.hondapowerequipment.com/products/generators/content.aspx?asset=gg_cycloconverter

I dare say few devices would be upset by that, but it's clearly nothing
like a pure sinewave.
** No *generator* ever puts out a square wave or modified square wave.

Did I say that it did? Don't think so.

Sylvia.
 
S

Sylvia Else

Jan 1, 1970
0
Robert said:
A few considerations:
1) Many inverters do NOT isolate; a relay drops out when the power
failes, and that turns on the inverter.

I was thinking specifically of the inverter based generators, which have
engine speeds that vary with load, but which maintain a constant
frequency and voltage. I presume they rectify the AC output from the
generator proper (or use a DC generator) then synthesise some
approximation to a sinewave in the same way that a battery input
inverter would.
2) AFAIK there are NO sine wave inverters, the best are pseudo-sine wave
and even that waveform is not suitable to some equipment - which might
be damaged.

I found this page discussing a Yamaha inverter based generator. It
includes oscilloscope traces of the output, which is clearly a pretty
good sinewave. I haven't been able to find any indication of the
technology used for this (unless it's the obvious method involving
filtering).

http://2manytoyz.com/yamaha2400.html

Sylvia.
 
S

Sylvia Else

Jan 1, 1970
0
Phil said:
"Sillier than Anyone Else"




** Totally irrelevant.

A " cyclo-converter " is also NOT a generator.

What is a "generator" Phil? A device that generates? The Honda device
chugs away happily (I assume) generating power. The cycloconverter is
part of the mechanism.

Sylvia.
 
N

Nico Coesel

Jan 1, 1970
0
Sylvia Else said:
Given the parlous state of Australia's power systems, I've been
considering buying a standby generator. One marketing point of some of
the inverter based models is their suitability for 'sensitive
electronics' with computers given as an example. This appears to be
based on the fact that they'll provide a consistent sinewave output.

But given that computers invariably use switch-mode power supplies, are
they actually going to care what waveform they see - from square wave
thru 'modified sinewave' thru pure sinewave?

Not really. A computer doesn't care much as long as the voltage is
within range. One thing to consider is that computers are a bad load
to a generator. As a rule of thumb you need a generator with at least
twice the VA rating as the total VA rating of all computers. Otherwise
the generator cannot keeps its rpm constant (starts speeding up and
slowing down).
 
P

Phil Allison

Jan 1, 1970
0
"Sillier than Anyone Else"
What is a "generator" Phil?


** In the CONTEXT where I used the word - it referred to a small, petrol
motor driven, single phase alternator.

You pig ignorant TROLL.



...... Phil
 
S

Sylvia Else

Jan 1, 1970
0
Phil said:
"Sillier than Anyone Else"



** In the CONTEXT where I used the word - it referred to a small, petrol
motor driven, single phase alternator.

That'd be right. Change the context without notice.

Sylvia.
 
P

Phil Allison

Jan 1, 1970
0
"Sillier than Anyone Else"
That'd be right. Change the context without notice.


** ROTFL !!

Wot a massive fucking NUT CASE & DAMN LIAR you are !!




....... Phil
 
S

Sylvia Else

Jan 1, 1970
0
Nico said:
Not really. A computer doesn't care much as long as the voltage is
within range. One thing to consider is that computers are a bad load
to a generator. As a rule of thumb you need a generator with at least
twice the VA rating as the total VA rating of all computers. Otherwise
the generator cannot keeps its rpm constant (starts speeding up and
slowing down).

I assume that's related to the harmonic load represented by switch mode
power supplies.

Circuits for significantly improving the harmonic performance have been
around for a decade, but I suppose little will happen until legislation
requires their use.

Sylvia.
 
N

Nobody

Jan 1, 1970
0
I assume that's related to the harmonic load represented by switch mode
power supplies.

I assume that was referring to the variation in power consumption between
busy and idle.
Circuits for significantly improving the harmonic performance have been
around for a decade, but I suppose little will happen until legislation
requires their use.

EU legislation has required their use for some time (2001, AFAICT).
Specifically, most power supplies above 75W must comply with
IEC/EN61000-3-2, with computer PSUs conforming to class D.

In practice, this means that a typical ATX PSU starts with a boost
converter whose current waveform is roughly sinusoidal, and in phase with
the line voltage.

Although this isn't required in the US, I would assume that most PSUs will
have been designed to meet EU standards anyhow (cf RoHS).

FWIW, an application note on PFC:

http://www.onsemi.com/pub_link/Collateral/HBD853-D.PDF
 
J

JosephKK

Jan 1, 1970
0
I assume that's related to the harmonic load represented by switch mode
power supplies.

Circuits for significantly improving the harmonic performance have been
around for a decade, but I suppose little will happen until legislation
requires their use.

Sylvia.

May not have happened yet down there, but has been around for about 2
decades in the US now.
 
J

JosephKK

Jan 1, 1970
0
I assume that was referring to the variation in power consumption between
busy and idle.


EU legislation has required their use for some time (2001, AFAICT).
Specifically, most power supplies above 75W must comply with
IEC/EN61000-3-2, with computer PSUs conforming to class D.

In practice, this means that a typical ATX PSU starts with a boost
converter whose current waveform is roughly sinusoidal, and in phase with
the line voltage.

Although this isn't required in the US, I would assume that most PSUs will
have been designed to meet EU standards anyhow (cf RoHS).

FWIW, an application note on PFC:

http://www.onsemi.com/pub_link/Collateral/HBD853-D.PDF

Power factor correction and harmonic suppression are two different
things. It is just convenient that typical PFC circuits also reduce
harmonics.
 
N

Nobody

Jan 1, 1970
0
Power factor correction and harmonic suppression are two different
things. It is just convenient that typical PFC circuits also reduce
harmonics.

True enough.

However, although the aforementioned "PFC" app note is titled "Power
Factor Correction (PFC) Handbook", it immediately starts by discussing
harmonics, EMI, and EN 61000-3-2 (which regulates harmonics rather than
power factor per se).

The EPSMA guide says:

The corresponding electronic circuitry is often called Power Factor
Correction (PFC) circuitry, although power factor correction is not the
correct wording but has become synonymous for harmonic line current
reduction

http://www.epsma.org/pdf/PFC Guide_April 2005.pdf

And then implicitly re-iterates the informal use by using the filename
"PFC Guide_April 2005.pdf", although the title is "Harmonic Current
Emissions - Guidelines to the standard EN 61000-3-2".
 
S

Sylvia Else

Jan 1, 1970
0
Nobody said:
I assume that was referring to the variation in power consumption between
busy and idle.

Could be, I suppose, though whether the generator can keep its RPM
constant (or rather, within acceptable bounds), would depend on how fast
it can change its throttle setting.

Sylvia.
 
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