Use of Modified Sine Wave Inverter During and Emergency - st

[Bill]

After the recent blackout in the NE USA, I bought a 1000 Watt (2000 Watt peak)
modified sine wave power inverter for use during emergencies - from car or car
battery. (PowerBright AED1000) (Incidentally, the waveform from their manual
looks more like a modified square wave - a square wave with a brief pause at
zero when the voltage changes from+ to -. But that may be poor graphics.)

I was thinking of a strategy of how to use this during a major, extended
blackout. Things like a laptop (after the battery runs down), small energy
saver light, 400 watt microwave, fan, etc. if I want to expend the power seem
fine. The thing I'm stuck on is the refrigerator. It is a pretty old model.
4.3 amps. (For complicated reasons, I don't want to replace it.) I've been
reading that modified sine wave inverters can burn out motors. So I'm worried
about that. I was thinking of a strategy of running it maybe 45 mins. "on"
than 1 hr. "off". Do refrigerators have protection against motors overheating?
Is this a reasonable risk? Do you think this strategy is reasonable?

Thanks in advance for any help.

Bill

 

[Watson A.Name - "Watt Sun]

In article <AOb4b.2952$Kx5.9@newssvr33.news.prodigy.com>, xxx@yy.zz
mentioned...

After the recent blackout in the NE USA, I bought a 1000 Watt (2000 Watt peak)
modified sine wave power inverter for use during emergencies - from car or car
battery. (PowerBright AED1000) (Incidentally, the waveform from their manual
looks more like a modified square wave - a square wave with a brief pause at
zero when the voltage changes from+ to -. But that may be poor graphics.)

I was thinking of a strategy of how to use this during a major, extended
blackout. Things like a laptop (after the battery runs down), small energy
saver light, 400 watt microwave, fan, etc. if I want to expend the power seem
fine. The thing I'm stuck on is the refrigerator. It is a pretty old model.
4.3 amps. (For complicated reasons, I don't want to replace it.) I've been
reading that modified sine wave inverters can burn out motors. So I'm worried
about that. I was thinking of a strategy of running it maybe 45 mins. "on"
than 1 hr. "off". Do refrigerators have protection against motors overheating?
Is this a reasonable risk? Do you think this strategy is reasonable?

I think you might get better answers on the ng alt.solar.photovoltaic,
where many people have experience with this kind of problem.

First off, there's nothing saying you can't just use bags of ice in
the fridge in an emergency, to keep it cool for a long time. The 45
min cycling isn't going to help because the fridge will run for
however long it takes to do the job, which may be shorter than 45
mins. Then you ask us to answer potentially liable questions about
your fridge, and you don't even tell us the make and model. I say go
for it, plug it in and run it for a day, and see how it works. If it
burns out, you have a good excuse to buy a new one that will work
okay.

A lady at work replaced her old fridge with a new energy efficient
one, and saved fifty bucks a month on electricity bills. Really!

So, plug the cheap fan in and see if it overheats. A lot cheaper to
replace than the fridge! But you don't really need an inverter for
lamps and fans, which can be the types that run directly off 12VDC.
Same with the laptop. The microwave? Just put it in the gas oven and
heat it up!

Sometimes I think we should all be a little less dependent on
electricity. :-/

BTW, nothing wrong with a Coleman lantern. Except it has some
radioactive thorium in the mantle, so don't sleep on it, or you'll
start glowing too! Does anyone know why this is so? Regular
incandescent lamps have tungsten filaments, how come they're not
radioactive too? What does the mantle have that an incandescent lamp
doesn't have? Maybe I should check out How Things Work or something..

Thanks in advance for any help.

Bill

--
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Just when you thought you had all this figured out, the gov't
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[Zak]

Watson A.Name - Watt Sun wrote:

BTW, nothing wrong with a Coleman lantern. Except it has some
radioactive thorium in the mantle, so don't sleep on it, or you'll
start glowing too! Does anyone know why this is so? Regular
incandescent lamps have tungsten filaments, how come they're not
radioactive too?

Tungsten is not thorium. And the gas mantles use the oxide, not the
metal. Interesting stuff, these mantles. You want them to run white hot,
and have some strength as well. A quick google leads me to believe they
are fabric (which burns away of course) impregnated with cerium (1%) and
thorium oxide (99%).

In any case they are now available 'thorium free'. See
http://www.primus.se/EN/products/product_730800.html. It seems Yttrium
is the replacement. See http://www.du.edu/~jcalvert/phys/rare.htm.


Thomas

 

[the Wiz]

"Bill" <xxx@yy.zz> wrote:

After the recent blackout in the NE USA, I bought a 1000 Watt (2000 Watt peak)
modified sine wave power inverter for use during emergencies - from car or car
battery. (PowerBright AED1000) (Incidentally, the waveform from their manual
looks more like a modified square wave - a square wave with a brief pause at
zero when the voltage changes from+ to -. But that may be poor graphics.)

I was thinking of a strategy of how to use this during a major, extended
blackout. Things like a laptop (after the battery runs down), small energy
saver light, 400 watt microwave, fan, etc. if I want to expend the power seem
fine. The thing I'm stuck on is the refrigerator. It is a pretty old model.
4.3 amps. (For complicated reasons, I don't want to replace it.) I've been
reading that modified sine wave inverters can burn out motors. So I'm worried
about that. I was thinking of a strategy of running it maybe 45 mins. "on"
than 1 hr. "off". Do refrigerators have protection against motors overheating?
Is this a reasonable risk? Do you think this strategy is reasonable?

Thanks in advance for any help.

Bill

You may not be able to run the refrigerator at all, because of the high starting
current of some motors (several times the running current).
You might consider one of the thermoelectric (Peltier junction) coolers as your
emergency refrigerator, as they run directly off 12 volts.

Unless you have a very large battery, or plan to run the car's engine a lot, you
won't get much run-time. A typical car battery may be rated at 60 or 80
amp/hours which is the amount of power it can deliver at a low drain (20 [?]
hour rate). The available power is less at higher discharge rates. A battery
that can deliver 3 amps for 20 hours (60 amp/hours) can't deliver 60 amps for 1
hour even though the math appears the same, because of the underlying chemical
processes.

Back-of-an-envelope math
400 watt microwave is perhaps 70% efficient, thus requiring 400/.7=571 watts
input
Inverter is perhaps 80% efficient, thus 571 watts out requires 571/.8=713 watts
in
713 watts/12 volts=60 amps
Using the microwave for 12 minutes (0.2 hour) 60*.2=12amp/hours but the actual
power usage is probably 1.5 or 2 times higher because of the lower battery
efficiency at high current drain. Basically, one frozen dinner will use more
than 20% of the battery capacity.

As the current drain increases, the battery terminal voltage decreases because
of internal resistance. The inverter may be able to compensate for some battery
voltage drop by drawing more current, which will further decrease the battery
voltage and its total deliverable power.

More about me: http://thelabwiz.home.mindspring.com/
VB3 source code: http://thelabwiz.home.mindspring.com/vbsource.html
VB6 source code: http://thelabwiz.home.mindspring.com/vb6source.html
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Drivers for Pablo graphics tablet and JamCam cameras: http://home.earthlink.net/~mwbt/
johnecarter atat mindspring dotdot com. Fix the obvious to reply by email.

 

Watson A.Name - "Watt Sun" <alondra101@hotmail.com> wrote:

BTW, nothing wrong with a Coleman lantern. Except it has some
radioactive thorium in the mantle, so don't sleep on it, or you'll
start glowing too! Does anyone know why this is so?

IIRC it is due to the thorium having a useful optical emission spectrum
at comparatively low tempetures.

Regular
incandescent lamps have tungsten filaments, how come they're not
radioactive too?

About 40% of tungsten is a radioactive isotope!
(This only tells 1/2 the story, the activity is very low).

What does the mantle have that an incandescent lamp
doesn't have?

Gas to survive in an oxidising enviroment when you turn the lamp off and
also has to survive in a nasty mixed enviroment when the lamp is operating.
Also it runs somewhat cooler then a tungsten source!

Regards, Dan.
--
** The email address *IS* valid, do NOT remove the spamblock
And on the evening of the first day the lord said...........
..... LX 1, GO!; and there was light.

 

[the Wiz]

You should be able to find the answers here:
http://www.vidcam.com.au/sales/inverter.htm
or here:
http://www.windsun.com/Inverters/Inverter_selection.htm

They sell big inverters and have numerous recommendations about various
equipment. Not all of the world has readily available electricity 99.9% of the
time - some places rely on sun and wind for all their electricity.

If you read all the linked info, you'll find that the refrigerator will draw
about 15% - 20% more power (and thus probably get somewhat hotter) than it would
on commercial power. This shouldn't be a problem in intermittent operation. If
the room temperature is above 90F, the refrigerator might be running almost
continuously, depending on the quality of its insulation.

Before experiencing a long-term outage, put a thermometer on the compressor and
see how hot it gets in normal operation. Then connect it to the inverter for an
hour or so and see if there is an appreciable difference. If it runs hotter
than you would like, consider adding a small fan to provide cooling for the
compressor.


Other links of interest:
http://www.sweetwater.com/insync/techtip/04/16/2002

http://www.ibiblio.org/pub/academic/environment/alternative-energy/energy-resources/homepower-magazine/archives/1/01pg22.txt

http://www.majorpower.com/inverters/inverter_faq.pdf

http://www.advancedenergyonline.com/catalog/appliances/refrigeration.htm (search
for Conserv)



"Bill" <yyy@yyy.yyy> wrote:

"the Wiz" <look@message.body> wrote in message
news:rcd4lvguqfdni4ndsu1acpfao78p9ava5d@4ax.com...
"Bill" <xxx@yy.zz> wrote:

After the recent blackout in the NE USA, I bought a 1000 Watt (2000 Watt
peak)
modified sine wave power inverter for use during emergencies - from car or
car
battery. (PowerBright AED1000) (Incidentally, the waveform from their
manual
looks more like a modified square wave - a square wave with a brief pause
at
zero when the voltage changes from+ to -. But that may be poor graphics.)

I was thinking of a strategy of how to use this during a major, extended
blackout. Things like a laptop (after the battery runs down), small energy
saver light, 400 watt microwave, fan, etc. if I want to expend the power
seem
fine. The thing I'm stuck on is the refrigerator. It is a pretty old model.
4.3 amps. (For complicated reasons, I don't want to replace it.) I've been
reading that modified sine wave inverters can burn out motors. So I'm
worried
about that. I was thinking of a strategy of running it maybe 45 mins. "on"
than 1 hr. "off". Do refrigerators have protection against motors
overheating?
Is this a reasonable risk? Do you think this strategy is reasonable?

Thanks in advance for any help.

Bill


You may not be able to run the refrigerator at all, because of the high
starting
current of some motors (several times the running current).
You might consider one of the thermoelectric (Peltier junction) coolers as
your
emergency refrigerator, as they run directly off 12 volts.

Unless you have a very large battery, or plan to run the car's engine a lot,
you
won't get much run-time. A typical car battery may be rated at 60 or 80
amp/hours which is the amount of power it can deliver at a low drain (20 [?]
hour rate). The available power is less at higher discharge rates. A
battery
that can deliver 3 amps for 20 hours (60 amp/hours) can't deliver 60 amps
for 1
hour even though the math appears the same, because of the underlying
chemical
processes.

Back-of-an-envelope math
400 watt microwave is perhaps 70% efficient, thus requiring 400/.7=571 watts
input
Inverter is perhaps 80% efficient, thus 571 watts out requires 571/.8=713
watts
in
713 watts/12 volts=60 amps
Using the microwave for 12 minutes (0.2 hour) 60*.2=12amp/hours but the
actual
power usage is probably 1.5 or 2 times higher because of the lower battery
efficiency at high current drain. Basically, one frozen dinner will use
more
than 20% of the battery capacity.

As the current drain increases, the battery terminal voltage decreases
because
of internal resistance. The inverter may be able to compensate for some
battery
voltage drop by drawing more current, which will further decrease the
battery
voltage and its total deliverable power.



Perphaps I should have clarified, I have a spare battery for the car (actually
2 if you count the second car) and I plan to use that to run small things.
After a while I would start up the car's engine, connect the inverter to it
and plug the refrigerator into it. I would then start up the refrigerator. I
think there will be enough power since the the refrigerrator is 4.3 amps and
the inverter has a peak rating of 2000 watts (1000 continuous). In any case,
it is a reasonable assumption that it might start.

I would then also connect the second (spare) battery that I have been using to
recharge that too.

My question again concerns the possibility of the inverter causing the
refrigerator moter to overheat and burn out. Is this a reasonable possibility?
Do such moters have burnout protection? Would a strategy of 45 mins. on and 1
hr. off, protect against this?

Thanks.

Bill

More about me: http://thelabwiz.home.mindspring.com/
VB3 source code: http://thelabwiz.home.mindspring.com/vbsource.html
VB6 source code: http://thelabwiz.home.mindspring.com/vb6source.html
VB6 - MySQL how to: http://thelabwiz.home.mindspring.com/mysql.html
My newest language - NSBasic for the Palm PDA: http://thelabwiz.home.mindspring.com/nsbsource.html
Drivers for Pablo graphics tablet and JamCam cameras: http://home.earthlink.net/~mwbt/
johnecarter atat mindspring dotdot com. Fix the obvious to reply by email.

 

[Bill]

Thanks. I think I have a much better sense of this. I'm surprised inverters
are not more popular.

Bill

"the Wiz" <look@message.body> wrote in message
news:qkv4lvgvct0jncccs8r7dlngfe8mnopi6l@4ax.com...

You should be able to find the answers here:
http://www.vidcam.com.au/sales/inverter.htm
or here:
http://www.windsun.com/Inverters/Inverter_selection.htm

They sell big inverters and have numerous recommendations about various
equipment. Not all of the world has readily available electricity 99.9% of
the
time - some places rely on sun and wind for all their electricity.

If you read all the linked info, you'll find that the refrigerator will draw
about 15% - 20% more power (and thus probably get somewhat hotter) than it
would
on commercial power. This shouldn't be a problem in intermittent operation.
If
the room temperature is above 90F, the refrigerator might be running almost
continuously, depending on the quality of its insulation.

Before experiencing a long-term outage, put a thermometer on the compressor
and
see how hot it gets in normal operation. Then connect it to the inverter
for an
hour or so and see if there is an appreciable difference. If it runs hotter
than you would like, consider adding a small fan to provide cooling for the
compressor.


Other links of interest:
http://www.sweetwater.com/insync/techtip/04/16/2002


http://www.ibiblio.org/pub/academic/environment/alternative-energy/energy-resources/homepower-magazine/archives/1/01pg22.txt

http://www.majorpower.com/inverters/inverter_faq.pdf

http://www.advancedenergyonline.com/catalog/appliances/refrigeration.htm
(search
for Conserv)



"Bill" <yyy@yyy.yyy> wrote:


"the Wiz" <look@message.body> wrote in message
news:rcd4lvguqfdni4ndsu1acpfao78p9ava5d@4ax.com...
"Bill" <xxx@yy.zz> wrote:

After the recent blackout in the NE USA, I bought a 1000 Watt (2000 Watt
peak)
modified sine wave power inverter for use during emergencies - from car
or
car
battery. (PowerBright AED1000) (Incidentally, the waveform from their
manual
looks more like a modified square wave - a square wave with a brief
pause
at
zero when the voltage changes from+ to -. But that may be poor
graphics.)

I was thinking of a strategy of how to use this during a major, extended
blackout. Things like a laptop (after the battery runs down), small
energy
saver light, 400 watt microwave, fan, etc. if I want to expend the power
seem
fine. The thing I'm stuck on is the refrigerator. It is a pretty old
model.
4.3 amps. (For complicated reasons, I don't want to replace it.) I've
been
reading that modified sine wave inverters can burn out motors. So I'm
worried
about that. I was thinking of a strategy of running it maybe 45 mins.
"on"
than 1 hr. "off". Do refrigerators have protection against motors
overheating?
Is this a reasonable risk? Do you think this strategy is reasonable?

Thanks in advance for any help.

Bill


You may not be able to run the refrigerator at all, because of the high
starting
current of some motors (several times the running current).
You might consider one of the thermoelectric (Peltier junction) coolers
as
your
emergency refrigerator, as they run directly off 12 volts.

Unless you have a very large battery, or plan to run the car's engine a
lot,
you
won't get much run-time. A typical car battery may be rated at 60 or 80
amp/hours which is the amount of power it can deliver at a low drain (20
[?]
hour rate). The available power is less at higher discharge rates. A
battery
that can deliver 3 amps for 20 hours (60 amp/hours) can't deliver 60 amps
for 1
hour even though the math appears the same, because of the underlying
chemical
processes.

Back-of-an-envelope math
400 watt microwave is perhaps 70% efficient, thus requiring 400/.7=571
watts
input
Inverter is perhaps 80% efficient, thus 571 watts out requires 571/.8=713
watts
in
713 watts/12 volts=60 amps
Using the microwave for 12 minutes (0.2 hour) 60*.2=12amp/hours but the
actual
power usage is probably 1.5 or 2 times higher because of the lower
battery
efficiency at high current drain. Basically, one frozen dinner will use
more
than 20% of the battery capacity.

As the current drain increases, the battery terminal voltage decreases
because
of internal resistance. The inverter may be able to compensate for some
battery
voltage drop by drawing more current, which will further decrease the
battery
voltage and its total deliverable power.



Perphaps I should have clarified, I have a spare battery for the car
(actually
2 if you count the second car) and I plan to use that to run small things.
After a while I would start up the car's engine, connect the inverter to it
and plug the refrigerator into it. I would then start up the refrigerator.
I
think there will be enough power since the the refrigerrator is 4.3 amps
and
the inverter has a peak rating of 2000 watts (1000 continuous). In any
case,
it is a reasonable assumption that it might start.

I would then also connect the second (spare) battery that I have been using
to
recharge that too.

My question again concerns the possibility of the inverter causing the
refrigerator moter to overheat and burn out. Is this a reasonable
possibility?
Do such moters have burnout protection? Would a strategy of 45 mins. on and
1
hr. off, protect against this?

Thanks.

Bill


More about me: http://thelabwiz.home.mindspring.com/
VB3 source code: http://thelabwiz.home.mindspring.com/vbsource.html
VB6 source code: http://thelabwiz.home.mindspring.com/vb6source.html
VB6 - MySQL how to: http://thelabwiz.home.mindspring.com/mysql.html
My newest language - NSBasic for the Palm PDA:
http://thelabwiz.home.mindspring.com/nsbsource.html
Drivers for Pablo graphics tablet and JamCam cameras:
http://home.earthlink.net/~mwbt/
johnecarter atat mindspring dotdot com. Fix the obvious to reply by email.

 

[Watson A.Name - "Watt Sun]

In article <rcd4lvguqfdni4ndsu1acpfao78p9ava5d@4ax.com>,
look@message.body mentioned...

"Bill" <xxx@yy.zz> wrote:

After the recent blackout in the NE USA, I bought a 1000 Watt (2000 Watt peak)
modified sine wave power inverter for use during emergencies - from car or car
battery. (PowerBright AED1000) (Incidentally, the waveform from their manual
looks more like a modified square wave - a square wave with a brief pause at
zero when the voltage changes from+ to -. But that may be poor graphics.)

I was thinking of a strategy of how to use this during a major, extended
blackout. Things like a laptop (after the battery runs down), small energy
saver light, 400 watt microwave, fan, etc. if I want to expend the power seem
fine. The thing I'm stuck on is the refrigerator. It is a pretty old model.
4.3 amps. (For complicated reasons, I don't want to replace it.) I've been
reading that modified sine wave inverters can burn out motors. So I'm worried
about that. I was thinking of a strategy of running it maybe 45 mins. "on"
than 1 hr. "off". Do refrigerators have protection against motors overheating?
Is this a reasonable risk? Do you think this strategy is reasonable?

Thanks in advance for any help.

Bill


You may not be able to run the refrigerator at all, because of the high starting
current of some motors (several times the running current).
You might consider one of the thermoelectric (Peltier junction) coolers as your
emergency refrigerator, as they run directly off 12 volts.

Better yet, the fridges they put into RVs, trailers, etc. run off
propane. No need for messy batteries, generators, or gasoline.

From what I remember about peltier coolers, they are terribly
inefficient, too. They make a lot of heat, which has to go somewhere.
So that has to be dealt with. If you use one indoors, then it may
heat the place up a lot.

I remember moving those Servel gas fridges in the '70s and they were
terribly heavy, probably twice as heavy as an electric. My mom used
to make bread and put it on top of the fridge to keep it warm while it
did its "rise" thing. I vaguely remember the aroma of that rising
bread.

[snip]

--
@@F@r@o@m@@O@r@a@n@g@e@@C@o@u@n@t@y@,@@C@a@l@,@@w@h@e@r@e@@
###Got a Question about ELECTRONICS? Check HERE First:###
http://users.pandora.be/educypedia/electronics/databank.htm
My email address is whitelisted. *All* email sent to it
goes directly to the trash unless you add NOSPAM in the
Subject: line with other stuff. alondra101 <at> hotmail.com
Don't be ripped off by the big book dealers. Go to the URL
that will give you a choice and save you money(up to half).
http://www.everybookstore.com You'll be glad you did!
Just when you thought you had all this figured out, the gov't
changed it: http://physics.nist.gov/cuu/Units/binary.html
@@t@h@e@@a@f@f@l@u@e@n@t@@m@e@e@t@@t@h@e@@E@f@f@l@u@e@n@t@@

 

[Watson A.Name - "Watt Sun]

In article <JPs4b.3657$xj3.1290@newssvr32.news.prodigy.com>,
yyy@yyy.yyy mentioned...
[snip]

My question again concerns the possibility of the inverter causing the
refrigerator moter to overheat and burn out. Is this a reasonable possibility?
Do such moters have burnout protection? Would a strategy of 45 mins. on and 1
hr. off, protect against this?

I dunno if you got my previous followup. The fridge itself controls
the on-off duty cycle, so trying to control it yourself is probably
not going to help. Suppose you let the fridge run by itself. It
might run for 15 minutes and then shut off for 30. By unplugging it,
you may be forcing it to run longer thus making it get hotter.

Thanks.

Bill

--
@@F@r@o@m@@O@r@a@n@g@e@@C@o@u@n@t@y@,@@C@a@l@,@@w@h@e@r@e@@
###Got a Question about ELECTRONICS? Check HERE First:###
http://users.pandora.be/educypedia/electronics/databank.htm
My email address is whitelisted. *All* email sent to it
goes directly to the trash unless you add NOSPAM in the
Subject: line with other stuff. alondra101 <at> hotmail.com
Don't be ripped off by the big book dealers. Go to the URL
that will give you a choice and save you money(up to half).
http://www.everybookstore.com You'll be glad you did!
Just when you thought you had all this figured out, the gov't
changed it: http://physics.nist.gov/cuu/Units/binary.html
@@t@h@e@@a@f@f@l@u@e@n@t@@m@e@e@t@@t@h@e@@E@f@f@l@u@e@n@t@@

 

[CWatters]

"Bill" <yyy@yyy.yyy> wrote in message
news:JPs4b.3657$xj3.1290@newssvr32.news.prodigy.com...

Would a strategy of 45 mins. on and 1 hr. off, protect against this?

No. It will probably make the problem worse (if there is one).

After 1 hour off the fridge might need to be on for longer to recover the
temp loss. .Let the thermostat in the fridge control the duty cycle.