y do you knowitall trolls always change the subject when someone is
about to prove you wrong?
I know perfectly well what they are. The point is that what they are is
absolutely NOT '*implies a certain mode of operation*'.
the biggest threat to humanity comes from socialism, which has utterly
diverted our attention away from what really matters to our existential
On 10/12/2015 15:20, The Natural Philosopher wrote:
What are you trying to prove? Giving a partial description of a device
and out of context as well doesn't prove a point. There are hundreds of
terms that you can do this with such as Foster (seeley
discriminator);Black (level clamping);Line (flyback EHT) or Line (output
level) . Doesn't prove anything.
Have you heard the one about the man who bought two 9v batteries and
connected them in series to make a voltage doubler?
On 10/12/2015 12:42, email@example.com wrote:
Well you see, the reason many people describe such circuits as doublers,
is because you stick in an AC signal with a peak voltage of V in, and
you get out DC at 2V. This is contrary to the usual behaviour of a
linear unregulated supply where it will have a no load voltage output of
You can find similar circuits that can give triple or greater multiples
Do a web search for "voltage doubler", and you will find many circuits
like that which you describe.
Now why everyone is throwing toys out of the pram over the precise
naming of these circuits escapes me, since its bleeding obvious that
while "voltage doubler" is indeed in very common use, there are
different names and terminologies commonly in use as well.
A dubious claim IMHO, but not relevant, so let's skip that.
Yes, and calling it a doubler is also perfectly acceptable.
However don't take my word for it, see fig 1.78 and following explanation:
On Mon, 07 Dec 2015 18:36:20 +0000, TomSawer wrote:
I wouldn't hold your breath waiting for an answer. Seems some folk here
don't know the very considerable (x2) difference between peak voltage and
peak-to-peak voltage. I suspect that's the root of their comprehension
Ed's description was fine - the pedants might argue at the use of the
word "bridge" while describing the half wave rectification, but it ought
to be clear what was intended:
---------+----->|--------+----------- +V peak
| | |
| | | +
230 | --- C1
VAC | ---
| | |
| | |
| | +
| --- C2
| D2 |
-----|<--------+----------- -V peak
On the positive half of the cycle, D1 conducts and C1 charges to the
peak of the supply voltage. On the negative portion of the cycle, D2
conducts and charges C2 to the peak of the supply voltage. The voltage
measured over the series pair of capacitors will now equate to the peak
to peak voltage (i.e. twice the peak voltage)
On Sat, 05 Dec 2015 10:51:42 +0000, The Natural Philosopher wrote:
Well, that saved me the bother of putting you straight on that
'schoolboy howler'. :-)
Assuming the speaker is rated to handle 7KW transients, you might have
to endure 50Hz at high SPL for several seconds before the plugtop fuse
blows or the voice coil releases its magic smoke with a side order of
More realistically, with 50 to 100 watt rated units, the magic smoke
with pyrotechnic display event is likely to occur in less than quarter of
a cycle (5ms) so more a 'crack' and a flash of light with a side order of
magic smoke than a deafening thump.
It really depends on the size and rating of the speaker drive unit
involved. With smaller 2 inch half watt units, the flexible voice coil
tails will probably act as fusewire, rapidly curtailing any speaker cone
excursions and pyrotechnics.
It's only interesting the first time around with most domestic sized
speaker drive units. Beyond that, it all becomes somewhat predictable and
therefore a bore, unless you're paying Russ Andrews prices - then the
transactions on your bank account will be where the real action lies. :-)
Even assuming the use of a 250Vac X class capacitor (typically also
rated for a maximum stress rating of 630VDC and intended to be connected
directly across the mains input terminals) in a mains filter designed to
act as an LPF with a cut off transition frequency of 90 or 130 Hz, you're
likely to suffer a spectacular failure from voltage magnification
generating kilovolts within the filter circuit.
I could've added that rather obtuse acronym, DAMHIK, made more obtuse by
the lack of the qualifying phrase, "I just know :-)" but I won't :-).
Quite simply, when I was trying to eliminate what I thought were
troublesome 2nd and 3rd harmonics from a petrol generator emergency supply
, I designed and made up a LPF using mains voltage rated capacitors
which I'd had the foresight to test on a 6 VAC supply before trying to
use them in anger. After measuring ac voltages in the range of 30 volts
and above, I swiftly realised this wasn't going to be the right solution
 for me. :-)
I assume Brian's "Mains Filter" was the more prosaic "EMI" filter
designed to filter out 100KHz and above noise and transients on a 240v
50/60Hz mains supply where the magnification effect only applies to a few
hundred millivolts worth of unwanted HF energy that might be present on
the supply. I'm guessing Brian simply overlooked the fact that the
equivalent DC voltage rating for a capacitor to safely handle 250 volts ac
typically being in the region of 630 to 650 vdc.
 This is a dig at posters who, unconscionably, use the acronym, DAMHIK
*without* that all important phrase, "I just know :-)".
 The implication, often made in the literature accompanying most UPS
kit, that it's the 'poor quality' of mains voltage produced by such
emergency gensets which makes them unsuited for use with their UPS kit
(or a reference to a sensitivity adjustment that needs to be lowered to
mitigate such problems of "poor quality" emergency supplies), is rather
misleading in the extreme.
The truth of the matter is that all such gensets are extremely
susceptible to capacitive loading on their output over-riding the AVR
causing them to over-volt considerably (4.7microfarad capacitor across
the terminals of a 230v 2.8KVA genset resulting in 280v AC ouptut - the
2KVA Line Interactive UPS in question switching some 9 microfarads across
the supply when in pass mode, dropping it when switched to battery - you
can imagine the consequences of this set up - I didn't have to, endless
cycling between battery and 'mains power').
The problem of "Poor Quality" has nothing whatsoever to do with harmonic
content (2nd and 3rd harmonic and the sub-harmonic component resulting in
the use of a single cylinder 3000 rpm prime mover imposing its own 25Hz
modulation along with windings slot ripple effects). Nor has it anything
to do with the less than perfect frequency and voltage regulation
performance of such emergency gensets. It's all to do with capacitive
loading sensitivity of the AVR leading to uncontrolled overvolting.
A 'heads up' for those thinking of supplementing their whole house UPS
protected circuit mains sockets with an emergency genset is that the
*only* type that's free of this capacitive loading overvolting effect is
the "inverter" type such as the now classic Honda E3000 (or 3000E ...
whatever!) which uses a highly efficient permanent magnet alternator to
generate a DC voltage feeding a 50/60Hz 230vac inverter.
Luckily, Honda no longer hold a monopoly in the inverter genset market
and it's now possible to buy a brand new 3KVA inverter genset for less
than £1000 these days. The last time I checked pricing a couple or three
years ago, I was contemplating a spend of 600 quid or so for one such
genset before common sense prevailed.
It was one thing to buy a 2.8KVA petrol genset from Aldididle 6 or 7
years back for a bargain price of 150 quid (now down to 130 quid in more
recent offers) as a worthwhile supplement to my emergency backup supply
system but a totally different thing when looking to spend 4 or more
times that amount to get a 'solution that will *actually* work as
For anyone contemplating such a genset upgrade to their existing battery
backed UPS arrangements, it's important to realise that a basic genset
that uses a conventional 50/60Hz alternator driven by a 1500/1800 or
3000/3600rpm prime mover will be a complete waste of money unless you're
considering a 20 to 30 KVA monster to backup the whole house supply where
the 'protected' loading is less than a quarter of the genset's rating.
 Have you seen the price (and size and availability) of inductors and
capacitors rated to handle 30 kilovolts or more? I haven't but I figured
if I had to ask, I didn't need to know. :-)
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