"John G" wrote in message
...
It happens that Ned Simmons formulated :
On Fri, 10 Jul 2015 09:14:47 +1000, John G
wrote:
wrote :
On Thu, 9 Jul 2015 02:47:20 -0700 (PDT), robobass
wrote:
I know this is a metalworking site, but there is quite a bit of
expertise on subjects like this here. I just bought a
200/300Watt 230v inverter. I attached it to a car battery on
the bench (nothing else attached) and plugged in a few lamps.
The output measured 330v with loads of 50 and 150 watts. The
lights did seem brighter, but not excessively so. The voltmeter
is a cheapie, but seems generally accurate. I know that these
devices produce a modified sinewave, and I should expect a
different reading, but I thought the reading should be lower if
anything. Is this inverter a dud, or do I just not know how to
measure? Thanks
You should read about 0.7 x the rated voltage on a modified
square
wave inverter.
I am amazed no one has suggested using a good old Simpson 260 or
similar ANALOGUE meter and get the real answer.
All this waffle about transformers and peaks and average is
typical of the impractical answers so common in some of the
electronics groups.
KISS Keep It Simple Stupid. :-?
Won't work any better than the DVM, it'll just give yet another
misleading value.
are you sure?
My impractical waffle is to use two identical lamps with clear
envelopes, a variac, and a voltmeter. Connect one lamp to the
inverter
and the other to the variac. Arrange them so the filaments are
nearly
superimposed as you look thru both envelopes. Adjust the variac so
there's no difference in the color of the of the two filaments.
Measure the output voltage of the variac - that's the RMS output of
the inverter, within, I'll wager, a couple percent.
Switch the lamps and repeat the experiment to check for any
detectable
difference between them.
How many people who ask Electric Questions in a Metalwaork Group
have a Variac sitting around for such experiments?
--
John G Sydney.
I have Variacs and Powerstats from 3A to 20A, 140V and 280V, and
metalwaorked a new set of brass brushes for the 20A one. They are
basic necessities for alternate energy experimenting, along with
variable DC lab supplies. Yesterday I used a lab supply to see how
much USB current my "new" smart phone draws, before risking a laptop.
An SCR dimmer distorts the waveform and may not give the right answer.
The other test is to plug in everything you plan to use before you go,
to see if they survive.
-jsw