Getting to the point where an inverter starts to make more & more sense.
Phone charger, drill chargers, light bar charger etc.

Looking at these http://www.tlc-direct.co.uk/Products/TLINV300.html

It mentions in the spec "These inverters generate a modified sine wave,
which although not perfect, is considerably superior to the square waves
which are produced by most other inverters".

Is that a good thing?

It also mentions Peak power - 1000w Does that mean it would run an 800w
angle grinder for long enough to cut off a padlock or wheel clamp?


--
Dave - The Medway Handyman
www.medwayhandyman.co.uk

The Medway Handyman wrote:

Getting to the point where an inverter starts to make more & more sense.
Phone charger, drill chargers, light bar charger etc.

Looking at these http://www.tlc-direct.co.uk/Products/TLINV300.html

It mentions in the spec "These inverters generate a modified sine wave,
which although not perfect, is considerably superior to the square waves
which are produced by most other inverters".

Is that a good thing?

Generally yes - some things are not as happy being supplied with a
square wave (lots more harmonic noise).

It also mentions Peak power - 1000w Does that mean it would run an 800w
angle grinder for long enough to cut off a padlock or wheel clamp?

Probably not - it probably means there are enough FBC's in there to cope
with a big switch on surge. So it will get something running that draws
less than 300W normally but perhaps needs several times that to start.
Something with an induction motor like a fridge for example.



--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

In article ,
"The Medway Handyman" writes:
Getting to the point where an inverter starts to make more & more sense.
Phone charger, drill chargers, light bar charger etc.

Looking at these http://www.tlc-direct.co.uk/Products/TLINV300.html

I've got a 150W one of those (not from tlc). It runs a Potteron
Profile boiler and pump. Pump makes a bit of a strange noise due
to the harmonics, but it works fine.

The cigarette lighter plug gets very hot though. I've bought a
few high current connectors with a view of replacing it, but
they've all looked even more feeble than a cigarette lighter plug
when they've turned up, so I haven't really solved that one yet.
May just go for 30A binding posts and spade lugs.

You might want to check out a Maplin store. They did have loads
of inverters (including this range) going cheap (I suspect
cheaper than that TLC price).

It mentions in the spec "These inverters generate a modified sine wave,
which although not perfect, is considerably superior to the square waves
which are produced by most other inverters".

Is that a good thing?

Yes, but it's also marketing bull****. I've never seen an
inverter which produces square waves -- they all produce
a modified sine wave. This one basically adds an extended
zero crossing period which is as crude as you can get without
being a square wave. Some more advanced ones have a stepped
sine wave.

It also mentions Peak power - 1000w Does that mean it would run an 800w
angle grinder for long enough to cut off a padlock or wheel clamp?

No.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

In article ,
Andrew Gabriel wrote:
I've got a 150W one of those (not from tlc). It runs a Potteron
Profile boiler and pump. Pump makes a bit of a strange noise due
to the harmonics, but it works fine.

The cigarette lighter plug gets very hot though.

I'm not surprised - they're rated at 10 amps. ;-) The instructions with
most inverters say to use the supplied crock clips above a certain output.

I've bought a few high current connectors with a view of replacing it,
but they've all looked even more feeble than a cigarette lighter plug
when they've turned up, so I haven't really solved that one yet. May
just go for 30A binding posts and spade lugs.

Speakon type works fine.

--
*Tell me to 'stuff it' - I'm a taxidermist.

Dave Plowman London SW
To e-mail, change noise into sound.

It also mentions Peak power - 1000w *Does that mean it would run an 800w
angle grinder for long enough to cut off a padlock or wheel clamp?

For that purpose, this might be the tool:

http://cgi.ebay.co.uk/BOSCH-GWS-14-4...QQcmdZViewItem

"The Medway Handyman" wrote in message
...
Getting to the point where an inverter starts to make more & more sense.
Phone charger, drill chargers, light bar charger etc.

Looking at these http://www.tlc-direct.co.uk/Products/TLINV300.html

It mentions in the spec "These inverters generate a modified sine wave,
which although not perfect, is considerably superior to the square waves
which are produced by most other inverters".

Is that a good thing?

It also mentions Peak power - 1000w Does that mean it would run an 800w
angle grinder for long enough to cut off a padlock or wheel clamp?


--
Dave - The Medway Handyman
www.medwayhandyman.co.uk


"Is that a good thing ?" Well, it depends a lot on what you are intending
running on it. Personally, having seen some of the damage that can be done
by these things, I wouldn't recommend running anything 'electronic' on
anything other than a genuine sine wave. Some of the low quality switch mode
power supplies that are now used in some items - and *with* some items when
that power supply is an external type - are less than happy with anything
other than a sine wave going in. The main filter cap works very hard anyway
in these 'small' supplies, and asking it to work harder still as a result of
the raw DC being produced by the reccy being a very rough shape, is looking
for trouble down the line.

Also, linear power supplies that use a small mains transformer, often don't
like anything other than a genuine sine wave, because a bad waveshape can
drive the tranny to core saturation, with all the attendant nasties,
including overheating, which that can cause ...

Arfa

Dave Plowman (News) wrote:

Andrew Gabriel wrote:
The cigarette lighter plug gets very hot though.

I'm not surprised - they're rated at 10 amps. ;-)

And are generally crap. I find it surprising that the automotive
industry hasn't come up with a better 12 V accessory connector by now.
Most aspects of car electrics have improved hugely since the 1960s, but
that and the old car radio aerial plug remain as dinosaurs.

A 30 A rated connector using a system of fused plugs would be good...

--
Andy

On 2008-06-07 22:24:14 +0100, "The Medway Handyman"
said:

Getting to the point where an inverter starts to make more & more sense.
Phone charger, drill chargers, light bar charger etc.

Looking at these http://www.tlc-direct.co.uk/Products/TLINV300.html

It mentions in the spec "These inverters generate a modified sine wave,
which although not perfect, is considerably superior to the square waves
which are produced by most other inverters".

Is that a good thing?

It also mentions Peak power - 1000w Does that mean it would run an 800w
angle grinder for long enough to cut off a padlock or wheel clamp?

Yes, but then there would not be enough energy left in the battery to
turn over the engine.

Andy Wade wrote:
Dave Plowman (News) wrote:

Andrew Gabriel wrote:
The cigarette lighter plug gets very hot though.

I'm not surprised - they're rated at 10 amps. ;-)

And are generally crap. I find it surprising that the automotive
industry hasn't come up with a better 12 V accessory connector by now.

They have lots: but they are only used in caravans.

Most aspects of car electrics have improved hugely since the 1960s, but
that and the old car radio aerial plug remain as dinosaurs.

A 30 A rated connector using a system of fused plugs would be good...

In article ,
Andy Wade wrote:
Dave Plowman (News) wrote:

Andrew Gabriel wrote:
The cigarette lighter plug gets very hot though.

I'm not surprised - they're rated at 10 amps. ;-)

And are generally crap. I find it surprising that the automotive
industry hasn't come up with a better 12 V accessory connector by now.

Absolutely. I hate the things.

Most aspects of car electrics have improved hugely since the 1960s, but
that and the old car radio aerial plug remain as dinosaurs.

Mine has F-type. ;-)

A 30 A rated connector using a system of fused plugs would be good...

I suppose that's probably the reason the cigar lighter ones have continued
- easy design to have a readily changeable fuse in.

But how often would you need a 30 amp take off inside the car? The common
need is for things like phone chargers and I-pods. So a much smaller
connector would be fine. I fitted a standard 2.5mm power connector for the
Tom-Tom in the dash top and incorporated the charger out of sight. Having
a cable draped over the dash really annoyed me.

--
*Work like you don't need the money. Love like you've never been hurt.

Dave Plowman London SW
To e-mail, change noise into sound.

Dave Plowman (News) wrote:

Mine has F-type. ;-)

Very sensible. That's a DAB radio, IIRC.

But how often would you need a 30 amp take off inside the car?

Well, whatever figure you choose, someone will want more. 30 A was just
my guess at a reasonable limit and it's only about 400 watts. Enough to
run small mains appliances through an inverter, or for a one-cup
immersion heater for brewing up, or for 12 V power tools such as those
little compressors, electric winches, and so on.

These days you could have a current limit set under software control,
like USB. 5 or 10 A max., say, when the engine isn't running and 30 A
when it is.

Whatever happened to 36/42 volt car electrics, which have been "only
just round the corner" for the last couple of decades?

--
Andy

On Jun 7, 10:24*pm, "The Medway Handyman"
wrote:

Getting to the point where an inverter starts to make more & more sense.
Phone charger, drill chargers, light bar charger etc.

Looking at thesehttp://www.tlc-direct.co.uk/Products/TLINV300.html

It mentions in the spec "These inverters generate a modified sine wave,
which although not perfect, is considerably superior to the square waves
which are produced by most other inverters".

Is that a good thing?

It also mentions Peak power - 1000w *Does that mean it would run an 800w
angle grinder for long enough to cut off a padlock or wheel clamp?

If pk output is 1kw, continuous output will be something like 300w, as
has been said.

Now an 800w angle grinder will consume a bit over 1kVA running due to
less than ideal power factor, and probably several times that during
startup. So your invertor is inadequte by a factor of 3 or more.

You can still run it on the inveror by using a dropper - but the
performance would be so dire the discs just cease to cut below a
certain speed, so you'd be there all day.

So no.

Oh, all cheap modern invertors produce msw, you wont find square waves
anywhere unless you go back several decades. MSW increases power
dissipation in motors, making matters worse.

For a padlock you could probably use a die grinder + a few discs.


NT

On Sun, 08 Jun 2008 13:23:23 +0100, Andy Wade wrote:

Well, whatever figure you choose, someone will want more. 30 A was just
my guess at a reasonable limit and it's only about 400 watts. Enough to
run small mains appliances through an inverter,

Plenty of 12v microwaves and TVs about. Check the truckers web sites...

for a one-cup immersion heater for brewing up,

I have a 12v kettle 2 mugs capacity takes about 20mins to boil. Pulls a
good 10A and the cable gets warm...

or for 12 V power tools such as those little compressors,

Got a "heavy duty" compressor as pumping up one of the tyres from 10psi
killed the previous ordinary one. This one is continusly rated, fan cooled
motor, doesn't have a rating but probably no more than 10A if that.

electric winches, and so on.

Ah a decent whinch takes far more than 30A...

These days you could have a current limit set under software control,
like USB.

KISS is better I feel. There has to be "smarts" in the kit and the car.
The current 10A is enough but a smaller better connector really is needed.

--
Cheers
Dave.

Andrew Gabriel wrote:
In article ,
"The Medway Handyman" writes:
snip
It mentions in the spec "These inverters generate a modified sine wave,
which although not perfect, is considerably superior to the square waves
which are produced by most other inverters".

Is that a good thing?

Yes, but it's also marketing bull****. I've never seen an
inverter which produces square waves -- they all produce
a modified sine wave. This one basically adds an extended
zero crossing period which is as crude as you can get without
being a square wave. Some more advanced ones have a stepped
sine wave.


All the ones I've ever looked at are made up from a bit of zero volts, a
bigger bit of plus volts, a bit of zero volts, then a bit of minus. If
you draw a graph with a very blunt pencil then take your glasses off and
put someone else on, then turn out the light you *might* think that's a
sine wave.

Nevertheless mine seemed to drive my laptop (which was old enough for me
not to care about killing it) for a week on a canal boat.

Andy

In article ,
Andy Champ writes:
Andrew Gabriel wrote:
In article ,
"The Medway Handyman" writes:
snip
It mentions in the spec "These inverters generate a modified sine wave,
which although not perfect, is considerably superior to the square waves
which are produced by most other inverters".

Is that a good thing?

Yes, but it's also marketing bull****. I've never seen an
inverter which produces square waves -- they all produce
a modified sine wave. This one basically adds an extended
zero crossing period which is as crude as you can get without
being a square wave. Some more advanced ones have a stepped
sine wave.


All the ones I've ever looked at are made up from a bit of zero volts, a
bigger bit of plus volts, a bit of zero volts, then a bit of minus. If
you draw a graph with a very blunt pencil then take your glasses off and
put someone else on, then turn out the light you *might* think that's a
sine wave.

Yes, that's exactly what this one does.

Nevertheless mine seemed to drive my laptop (which was old enough for me
not to care about killing it) for a week on a canal boat.

Most computer PSU's don't care. Actually, many would run
better off a square wave.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

"Andrew Gabriel" wrote in message
...
In article ,
Andy Champ writes:
Andrew Gabriel wrote:
In article ,
"The Medway Handyman" writes:
snip
It mentions in the spec "These inverters generate a modified sine wave,
which although not perfect, is considerably superior to the square
waves
which are produced by most other inverters".

Is that a good thing?

Yes, but it's also marketing bull****. I've never seen an
inverter which produces square waves -- they all produce
a modified sine wave. This one basically adds an extended
zero crossing period which is as crude as you can get without
being a square wave. Some more advanced ones have a stepped
sine wave.


All the ones I've ever looked at are made up from a bit of zero volts, a
bigger bit of plus volts, a bit of zero volts, then a bit of minus. If
you draw a graph with a very blunt pencil then take your glasses off and
put someone else on, then turn out the light you *might* think that's a
sine wave.

Yes, that's exactly what this one does.

Nevertheless mine seemed to drive my laptop (which was old enough for me
not to care about killing it) for a week on a canal boat.

Most computer PSU's don't care. Actually, many would run
better off a square wave.

On what do you base that ? A computer PSU is designed to run with a sine
wave input. It's like saying that my diesel car runs better if I put petrol
in it ...

Arfa

In article ,
"Arfa Daily" writes:
"Andrew Gabriel" wrote in message
Most computer PSU's don't care. Actually, many would run
better off a square wave.

On what do you base that ? A computer PSU is designed to run with a sine
wave input. It's like saying that my diesel car runs better if I put petrol
in it ...

Most computer power supplies are designed to cope with sine wave
input, because they have to. The first thing they do is to full
wave rectify it to DC. Sine wave is not a good starting point for
that -- you either end up with power factor well below 1, or you
have to use more complex circuitry to compensate (in larger
commercial computer PSU's). If you feed a square wave in, that's
pretty much as good as DC, and the power factor will be 1. If you
knew you were only going to feed the computer with square wave
(and/or higher frequency) and you didn't have to design the PSU to
run from 50Hz sine wave, you could make the PSU somewhat simpler
and more efficient. Actually, some mainframes used this for
decades, and required to be fed with 400Hz 3-phase, which made
PSU design much easier, and still more efficient even allowing
for a motor-generator set to create the 400Hz supply.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

On Jun 9, 10:55*am, (Andrew Gabriel)
wrote:
In article ,
* * * * "Arfa Daily" writes:

"Andrew Gabriel" wrote in message

Most computer PSU's don't care. Actually, many would run
better off a square wave.

On what do you base that ? A computer PSU is designed to run with a sine
wave input. It's like saying that my diesel car runs better if I put petrol
in it ...

Most computer power supplies are designed to cope with sine wave
input, because they have to. The first thing they do is to full
wave rectify it to DC. Sine wave is not a good starting point for
that -- you either end up with power factor well below 1, or you
have to use more complex circuitry to compensate (in larger
commercial computer PSU's). If you feed a square wave in, that's
pretty much as good as DC, and the power factor will be 1. If you
knew you were only going to feed the computer with square wave
(and/or higher frequency) and you didn't have to design the PSU to
run from 50Hz sine wave, you could make the PSU somewhat simpler
and more efficient. *Actually, some mainframes used this for
decades, and required to be fed with 400Hz 3-phase, which made
PSU design much easier, and still more efficient even allowing
for a motor-generator set to create the 400Hz supply.

All true nuff. On an invertor its a bit more complex though. An
invertor doesnt put out a square wave, its msw, ie there are 0v
periods between each rectangular pulse. During this 0v the reservoirs
partly discharge. Now with a sine input, V_mains climbs at a certain
rate, and this rate of climb limits the peak i flow during reservoir
recharging, along with C size and the various stray Rs around. But
when the reservoir is recharged from an msw wave, the waveshape does
not limit the recharging i. And since the psu is designed to run on
sine, there is nothing but an rfi filter to limit this i. The result
is a _very_ peaky current waveform. If wanted this could be tamed with
a small inductor.


NT

On 09 Jun 2008 09:55:39 GMT, Andrew Gabriel wrote:

and still more efficient even allowing for a motor-generator set to
create the 400Hz supply.

Er, I've never heard of an alternator that can produce a squarewave
output... Surely the physical nature of the beast (coils and magnetic
fields) means that the waveform is sine (or close to it).

Isn't the improved efficiency down to the higher frequency thus less
discharge of the reservoirs for a given load current?

--
Cheers
Dave.

Dave Liquorice wrote:
On 09 Jun 2008 09:55:39 GMT, Andrew Gabriel wrote:

and still more efficient even allowing for a motor-generator set to
create the 400Hz supply.

Er, I've never heard of an alternator that can produce a squarewave
output... Surely the physical nature of the beast (coils and magnetic
fields) means that the waveform is sine (or close to it).

Isn't the improved efficiency down to the higher frequency thus less
discharge of the reservoirs for a given load current?

I dont know the alternators or psus in question, I just wondered if
the cost & efficiency gain was down to smaller transformers
running at 400Hz, and of course smaller reservoir caps. 400Hz TFs
have much lower resistance windings for the same throughput.

Alternators dont produce square output of course, but they can
produce non-sine by using a commutator, fwiw. In principle this
could remove the need for a rectifier, but what actually was done
I dont know.


NT

On Jun 9, 12:16*pm, "Dave Liquorice"
wrote:
On 09 Jun 2008 09:55:39 GMT, Andrew Gabriel wrote:

and still more efficient even allowing for a motor-generator set to
create the 400Hz supply.

Er, I've never heard of an alternator that can produce a squarewave
output... Surely the physical nature of the beast (coils and magnetic
fields) means that the waveform is sine (or close to it).

Isn't the improved efficiency down to the higher frequency thus less
discharge of the reservoirs for a given load current?

ps fwiw motorgen sets were only around 60% efficient, so I dont see
how including one could ever improve the efficiency overall. Even in
the 1920s LT psus did better than that.


NT

In article
,
wrote:
Alternators dont produce square output of course, but they can
produce non-sine by using a commutator, fwiw. In principle this
could remove the need for a rectifier, but what actually was done
I dont know.

That's sort of how a car dynamo works.

--
*I didn't drive my husband crazy -- I flew him there -- it was faster

Dave Plowman London SW
To e-mail, change noise into sound.

In article et,
"Dave Liquorice" writes:
On 09 Jun 2008 09:55:39 GMT, Andrew Gabriel wrote:

and still more efficient even allowing for a motor-generator set to
create the 400Hz supply.

Er, I've never heard of an alternator that can produce a squarewave
output... Surely the physical nature of the beast (coils and magnetic
fields) means that the waveform is sine (or close to it).

Yes -- I wasn't very clear but I meant either a square wave
or a higher frequency sine wave was an improvement. A 50Hz
sine wave is a long way from ideal for a computer load.

Isn't the improved efficiency down to the higher frequency thus less
discharge of the reservoirs for a given load current?

Yes. Also whilst the power factor as you go into the rectifiers
may be quite low, the motor/gen set inertia completely hides
that from the utility supply, which sees near unity power factor.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

Arfa Daily wrote:
"Andrew Gabriel" wrote in message
...
In article ,
Andy Champ writes:
Andrew Gabriel wrote:
In article ,
"The Medway Handyman" writes:
snip
It mentions in the spec "These inverters generate a modified sine wave,
which although not perfect, is considerably superior to the square
waves
which are produced by most other inverters".

Is that a good thing?
Yes, but it's also marketing bull****. I've never seen an
inverter which produces square waves -- they all produce
a modified sine wave. This one basically adds an extended
zero crossing period which is as crude as you can get without
being a square wave. Some more advanced ones have a stepped
sine wave.

All the ones I've ever looked at are made up from a bit of zero volts, a
bigger bit of plus volts, a bit of zero volts, then a bit of minus. If
you draw a graph with a very blunt pencil then take your glasses off and
put someone else on, then turn out the light you *might* think that's a
sine wave.
Yes, that's exactly what this one does.

Nevertheless mine seemed to drive my laptop (which was old enough for me
not to care about killing it) for a week on a canal boat.
Most computer PSU's don't care. Actually, many would run
better off a square wave.

On what do you base that ? A computer PSU is designed to run with a sine
wave input. It's like saying that my diesel car runs better if I put petrol
in it ...


No, it isn't.Its in fact as it happens designed to run off anything
witha peak volatge of between about 300 and 400V,since all the PSU does
to start with is rectify what it sees and smooth it - if that is mains,
thats about 430VDC. It could just as easily BE 430VDC.

In fact I worked on a project once where the same power supply could be
used on 48VDC, 120VAC, 230VAC with no reconfiguration required.

In short everything from 48-250V AC or DC was able to make it work.

It's treansformers that get hot under the collar with non sine mains.
But even then not that much.

Arfa

wrote:
On Jun 9, 10:55 am, (Andrew Gabriel)
wrote:
In article ,
"Arfa Daily" writes:

"Andrew Gabriel" wrote in message

Most computer PSU's don't care. Actually, many would run
better off a square wave.
On what do you base that ? A computer PSU is designed to run with a sine
wave input. It's like saying that my diesel car runs better if I put petrol
in it ...
Most computer power supplies are designed to cope with sine wave
input, because they have to. The first thing they do is to full
wave rectify it to DC. Sine wave is not a good starting point for
that -- you either end up with power factor well below 1, or you
have to use more complex circuitry to compensate (in larger
commercial computer PSU's). If you feed a square wave in, that's
pretty much as good as DC, and the power factor will be 1. If you
knew you were only going to feed the computer with square wave
(and/or higher frequency) and you didn't have to design the PSU to
run from 50Hz sine wave, you could make the PSU somewhat simpler
and more efficient. Actually, some mainframes used this for
decades, and required to be fed with 400Hz 3-phase, which made
PSU design much easier, and still more efficient even allowing
for a motor-generator set to create the 400Hz supply.

All true nuff. On an invertor its a bit more complex though. An
invertor doesnt put out a square wave, its msw, ie there are 0v
periods between each rectangular pulse. During this 0v the reservoirs
partly discharge. Now with a sine input, V_mains climbs at a certain
rate, and this rate of climb limits the peak i flow during reservoir
recharging, along with C size and the various stray Rs around. But
when the reservoir is recharged from an msw wave, the waveshape does
not limit the recharging i. And since the psu is designed to run on
sine, there is nothing but an rfi filter to limit this i. The result
is a _very_ peaky current waveform. If wanted this could be tamed with
a small inductor.


...generally found on the inverter anyway to try and keep RFI out of the
picture.

NT

"The Natural Philosopher" wrote in message
...
Arfa Daily wrote:
"Andrew Gabriel" wrote in message
...
In article ,
Andy Champ writes:
Andrew Gabriel wrote:
In article ,
"The Medway Handyman" writes:
snip
It mentions in the spec "These inverters generate a modified sine
wave,
which although not perfect, is considerably superior to the square
waves
which are produced by most other inverters".

Is that a good thing?
Yes, but it's also marketing bull****. I've never seen an
inverter which produces square waves -- they all produce
a modified sine wave. This one basically adds an extended
zero crossing period which is as crude as you can get without
being a square wave. Some more advanced ones have a stepped
sine wave.

All the ones I've ever looked at are made up from a bit of zero volts,
a
bigger bit of plus volts, a bit of zero volts, then a bit of minus. If
you draw a graph with a very blunt pencil then take your glasses off
and
put someone else on, then turn out the light you *might* think that's a
sine wave.
Yes, that's exactly what this one does.

Nevertheless mine seemed to drive my laptop (which was old enough for
me
not to care about killing it) for a week on a canal boat.
Most computer PSU's don't care. Actually, many would run
better off a square wave.

On what do you base that ? A computer PSU is designed to run with a sine
wave input. It's like saying that my diesel car runs better if I put
petrol in it ...


No, it isn't.Its in fact as it happens designed to run off anything witha
peak volatge of between about 300 and 400V,since all the PSU does to start
with is rectify what it sees and smooth it - if that is mains, thats about
430VDC. It could just as easily BE 430VDC.

In fact I worked on a project once where the same power supply could be
used on 48VDC, 120VAC, 230VAC with no reconfiguration required.

In short everything from 48-250V AC or DC was able to make it work.

It's treansformers that get hot under the collar with non sine mains. But
even then not that much.



That's rather higher than any switch mode power supplies that I work on, for
the front end DC bus. Around 360v on the back side of the reccy is more
typical. In fact the highest one that I can think of is about 390v after a
front end resonant PFC stage.

This particular supply will work down to about 35v ac input, and still
produces 390v across the main filter cap with that level of input voltage.
However, it cannot deliver its rated output currents with that level of
input, and I'm surprise that the one you cite could, without any
reconfigurataion, as you say.

Many modern switchers work by the skin of their teeth and, whilst I agree
with what you say about the fundamental principal of deriving the front end
bus voltage *should* be independant of what you feed in, they are
never-the-less designed with a sine wave input, with a known and predictable
dv/dt, in mind, as that is what they would be expecting to see when on a
mains input.

Waves with fast transients and rise times, can wreak havoc with wound filter
components in the mains feed, and cause excess dissipation within filter
network caps, and VDRs. Sudden polarity changes and voltage steps, can also
bring the reccies close to or beyond their maximum ratings. Likewise, where
the value of the main filter cap for the front end bus, is small and barely
adequate for the job, as is often the case with small supplies, sudden
changes in polarity and voltage level applied to the bridge, may well cause
the cap's maximum ripple current rating to be exceeded.

Just a couple of weeks ago, I had a small switcher in for repair, which had
been put on a 'modified sine wave' inverter in a motorhome. The front end
was blown to pieces, having suffered a cascade failure. The owner assured me
that prior to this, the item has been working fine in his house for a couple
of years on that same power supply, and this was the first time that he had
put it in the motorhome.


Arfa

In article ,
"Arfa Daily" writes:
That's rather higher than any switch mode power supplies that I work on, for
the front end DC bus. Around 360v on the back side of the reccy is more
typical. In fact the highest one that I can think of is about 390v after a
front end resonant PFC stage.

You would normally see 340VDC from full wave rectifying 240VDC.
One which has caught out some people are bathroom shaver sockets.
They can deliver up to 270VAC at small power draw. Things like
saver/toothbrush chargers are well below the isolating transfomer's
full load rating, and can end up being fed with higher than expected
mains voltage (that would be 381VDC after rectifying). The
instructions for shaver sockets often advise using the 120V side for
low power draw appliances, but the instructions are chucked out by
the fitter and never seen by the householder;-)

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]