Inverter powering a fridge?

[The Real Andy]

On Mon, 3 May 2004 22:59:32 +1200, Patrick Dunford
<patrickdunford@nz.invalid> wrote:

A square wave is horizontal for a good percentage (in fact most) of its
cycle. A modified sine wave is actually multiple square waves, looks like
a stairway if you get my meaning - instead of going up all in one go it
goes a little bit up, a little bit across, and so on until it starts
going down the other side.

Actually, you are wrong. All inverters output square waves (a sine
wave with lots of harmonics). It is the frequency and duty cycle that
determines if it is a sine or modified sine inverter. It's easier to
do modified sine as the frequency is fixed, true sine becomes a little
trickier because the freqency varies quite a lot, hence more
complications in the circuit design.

 

[Phil Allison]

"Patrick Dunford" <patrickdunford@nz.invalid>

Phil Allison


** The modified sine wave or stepped square wave contains some odd
numbered harmonics of the 50 Hz fundamental frequency, but
considerably
less
than a simple square wave does.

In no way is there any DC component that would harm a motor or
transformer.

DC won't pass through a transformer,


** There is no DC component - none - zilch.

A square wave is horizontal for a good percentage (in fact most) of its
cycle.

** So ***fucking*** what
?????????????????????????????????????????????????????????????????????

A modified sine wave is actually multiple square waves, looks like
a stairway if you get my meaning - instead of going up all in one go it
goes a little bit up, a little bit across, and so on until it starts
going down the other side.

** You are just not learning .......

Go do a Google on " square wave inverter"





.................. Phil

 

[The Real Andy]

On Sun, 2 May 2004 21:34:06 +0800, "Rheilly Phoull"
<Rheilly@bigpong.com> wrote:

"Brian Goldsmith" <brian.goldsmith@nospamecho1.com.au> wrote in message
news:GK5lc.8350$TT.5359@news-server.bigpond.net.au...

"Dafydd" wrote :-
The newer energy efficient electric motors fitted to Samsung fridges
will
not run at all from sine wave.


****** What is this nonsense?????????

Brian Goldsmith


I think we got us a 'snakeoil' salesman here ??

I assume that the OP meant that newer fridges wont run on modified
sine inverters

 

[KLR]

On Sun, 02 May 2004 12:23:02 GMT, "Brian Goldsmith"
<brian.goldsmith@nospamecho1.com.au> wrote:

"Dafydd" wrote :-
The newer energy efficient electric motors fitted to Samsung fridges
will
not run at all from sine wave.


****** What is this nonsense?????????

Brian Goldsmith

maybe he meant "modified square wave" ?

 

[Johnny]

On Sun, 2 May 2004 21:41:44 +1000, "Phil Allison"
<philallison@optusnet.com.au> wrote:

"Patrick Dunford" <patrickdunford@nz.invalid> wrote in message


** The modified sine wave or stepped square wave contains some odd
numbered harmonics of the 50 Hz fundamental frequency, but considerably
less
than a simple square wave does.

In no way is there any DC component that would harm a motor or
transformer.

DC won't pass through a transformer,


** There is no DC component - none - zilch.



so for that part of the waveform, in
fact a considerable part (depends on the exact waveform of course) there
is no power in the transformer, which adds up to poor quality power out
the other end.


** You are totally mistaken. Transformers just LOVE square waves - it
is the MOST efficient way possible to drive them.

I don't believe that is true for iron core transformers that have high
losses due to eddy currents in the iron.

regards,
Johnny.

 

[Phil Allison]

"Johnny" <john_wr@NOSPAM.hotmail.com.>

On Sun, 2 May 2004 21:41:44 +1000, "Phil Allison"

** You are totally mistaken. Transformers just LOVE square waves -
it
is the MOST efficient way possible to drive them.

I don't believe that is true for iron core transformers that have high
losses due to eddy currents in the iron.

** Don't say that to the millions of iron cored transformers used in
square wave inverters.





............... Phil

 

[Glenn Garrett]

I ran my 310 litre fridge for years on a Trace 2400W modified square wave...
Also 33"TV, video players, PC, Yamaha surround sound stereo etc.

Glenn

 

[Dafydd]

That should have been 'modified sine'

--


"Brian Goldsmith" <brian.goldsmith@nospamecho1.com.au> wrote in message
news:GK5lc.8350$TT.5359@news-server.bigpond.net.au...

"Dafydd" wrote :-
The newer energy efficient electric motors fitted to Samsung fridges
will
not run at all from sine wave.


****** What is this nonsense?????????

Brian Goldsmith

 

[J]

"Ken Taylor" <ken@home.nz> wrote in message
news:l73lc.1052$8J.35929@news.xtra.co.nz...

"atec" <"atec77(notspam)"@hotmail.com> wrote in message
news:40949AD1.4A78BFCC@hotmail.com...
it should but its a very big spike , perhaps the switching device fails
with such a sudden surge , Im sure some one will be more conversant than
I , either way be assured the unit he is trying to use wont cut it.

Darren wrote:

Hi,

What about the inverter having a overload cut out, shouldnt that have
stoped
the inverter from blowing up?

Darren


The switcher is almost guaranteed to protect the breaker.

Ken


Yup, that's the rule. Actually, the breaker will be fine for a slow

overload. Just can't hack being switched to a major fault condition - which
is what the start current of the compressor will look like. Either use an
inverter with MUCH greater rating or arrange another form of current limiter
that can act faster. A series inductor or even resistor will limit the
inrush current...

 

[TonyP]

"Dafydd" <noemail@anywhere.com> wrote in message
news:56Xlc.20744$TT.19443@news-server.bigpond.net.au...

That should have been 'modified sine'

Right the first time. It's just a square wave with reduced duty cycle, so
it's a square wave modified to give voltage levels closer to a sine wave.
Since it was never a sine wave, it can't really be a modified sine wave,
despite advertising copy.

TonyP.