Have spent over 2 hours trying to find out if most or all microwaves do true
variable power output as opposed to the traditional cycling on & off to
attain different power levels, panasonic call this inverter technology, they
make it sound like they are the only ones that do it, have not been able to
determine if this is so yet, I searched webpages as well as the newsgroup
archives but frustratingly I could not find the answer to what I would have
thought would be a common question.

"wave" wave@waving wrote in message ...
Have spent over 2 hours trying to find out if most or all microwaves do
true
variable power output as opposed to the traditional cycling on & off to
attain different power levels, panasonic call this inverter technology,
they
make it sound like they are the only ones that do it, have not been able
to
determine if this is so yet, I searched webpages as well as the newsgroup
archives but frustratingly I could not find the answer to what I would
have
thought would be a common question.



The vast majority of microwaves cycle the magnetron, only the inverter type
can do true variable power. I don't know if only Panasonic does this, but
one way to tell would be the weight, a conventional transformer power supply
will be considerably heavier, and the ovens will be cheaper as well.

"James Sweet" wrote in message
news:MKLtd.650$Qp.314@trnddc01...

"wave" wave@waving wrote in message ...
Have spent over 2 hours trying to find out if most or all microwaves do
true
variable power output as opposed to the traditional cycling on & off to
attain different power levels, panasonic call this inverter technology,
they
make it sound like they are the only ones that do it, have not been able
to
determine if this is so yet, I searched webpages as well as the
newsgroup
archives but frustratingly I could not find the answer to what I would
have
thought would be a common question.



The vast majority of microwaves cycle the magnetron, only the inverter
type
can do true variable power. I don't know if only Panasonic does this, but
one way to tell would be the weight, a conventional transformer power
supply
will be considerably heavier, and the ovens will be cheaper as well.


Thanks, I have very little experience with microwaves but I have used a
panasonic with inverter technology and a much older microwave and the
panasonic was definitely better at cooking evenly etc..., don't know if this
was to do with the inverter technology or some other improvement in modern
microwaves but it makes some sense to me that the inverter technology would
give better cooking, a pity it is not standard among all microwaves then.

Thanks, I have very little experience with microwaves but I have used a
panasonic with inverter technology and a much older microwave and the
panasonic was definitely better at cooking evenly etc..., don't know if
this
was to do with the inverter technology or some other improvement in modern
microwaves but it makes some sense to me that the inverter technology
would
give better cooking, a pity it is not standard among all microwaves then.



It's expensive to build, that's why it's not standard so far, but give it
time. Cooking even-ness is more a matter of cavity and waveguide design than
the power supply, I don't know about you but I don't remember the last time
I used anything less than full power to cook in a microwave, the lower power
I've only used for defrosting. I still think the inverter power supply is
cool, I just don't think it'll have all that noticeable of an effect on
cooking.

In article jiMtd.657$Qp.220@trnddc01,
"James Sweet" wrote:

Cooking even-ness is more a matter of cavity and waveguide design than
the power supply, I don't know about you but I don't remember the last time
I used anything less than full power to cook in a microwave, the lower power
I've only used for defrosting.

Mine is a combo LG unit. I regularly use lower microwave power settings
in combination with the grill so thick cuts like chicken legs, for
example, are nicely browned on the outside while being properly cooked
on the inside.

I was also experimenting with different microwave settings for cooking
rice without having the water spill everywhere inside the oven.
Currently I do 3 minutes at 100% (it's an 850W oven), followed by 15
minutes or more at 60%, depending on the size of the serving. There's
still some spillage, but it manages to cook nicely.

"Lawrence D¹Oliveiro" wrote in message
...

| Mine is a combo LG unit. I regularly use lower microwave power settings
| in combination with the grill so thick cuts like chicken legs, for
| example, are nicely browned on the outside while being properly cooked
| on the inside.
|
| I was also experimenting with different microwave settings for cooking
| rice without having the water spill everywhere inside the oven.
| Currently I do 3 minutes at 100% (it's an 850W oven), followed by 15
| minutes or more at 60%, depending on the size of the serving. There's
| still some spillage, but it manages to cook nicely.

The sensor models do a great job on things like rice. They usually have a
setting for this.

N

I was also experimenting with different microwave settings for cooking
rice without having the water spill everywhere inside the oven.
Currently I do 3 minutes at 100% (it's an 850W oven), followed by 15
minutes or more at 60%, depending on the size of the serving. There's
still some spillage, but it manages to cook nicely.

Seems like cooking it the old fashined way over a stove would be quicker. g

Alan Harriman

"James Sweet" wrote in
news:MKLtd.650$Qp.314@trnddc01:




The vast majority of microwaves cycle the magnetron, only the inverter
type can do true variable power. I don't know if only Panasonic does
this, but one way to tell would be the weight, a conventional
transformer power supply will be considerably heavier, and the ovens
will be cheaper as well.



Price-wise that's strange,as it's cheaper to make a switcher than it is to
make a big,iron-core transformer. That's why most electronics went to
switchers;it's cheaper than 50/60hz iron transformers,especailly at higher
power levels.

--
Jim Yanik
jyanik-at-kua.net

"Jim Yanik" . wrote in message
.. .
| "James Sweet" wrote in
| news:MKLtd.650$Qp.314@trnddc01:

| The vast majority of microwaves cycle the magnetron, only the inverter
| type can do true variable power. I don't know if only Panasonic does
| this, but one way to tell would be the weight, a conventional
| transformer power supply will be considerably heavier, and the ovens
| will be cheaper as well.
|
| Price-wise that's strange,as it's cheaper to make a switcher than it is to
| make a big,iron-core transformer. That's why most electronics went to
| switchers;it's cheaper than 50/60hz iron transformers,especailly at higher
| power levels.

Judging by the weight I think many new ovens use switchers, but don't
modulate them.

N

"wave" wave@waving wrote in message ...
| Have spent over 2 hours trying to find out if most or all microwaves do
true
| variable power output as opposed to the traditional cycling on & off to
| attain different power levels, panasonic call this inverter technology,
they
| make it sound like they are the only ones that do it, have not been able
to
| determine if this is so yet, I searched webpages as well as the newsgroup
| archives but frustratingly I could not find the answer to what I would
have
| thought would be a common question.

I have one of these and AFAIK only Panasonic is using it. 'Genius' is their
trademark, inverter technology is not. It's a very powerful switchmode power
supply that varies the input power to the microwave. BTW, don't buy the
convection version - they are a swine to keep clean.

All other makes I know of cycle power to control cooking which does not work
as well for some items (oatmeal for one).

N

"NSM" writes:

"wave" wave@waving wrote in message ...
| Have spent over 2 hours trying to find out if most or all microwaves do
true
| variable power output as opposed to the traditional cycling on & off to
| attain different power levels, panasonic call this inverter technology,
they
| make it sound like they are the only ones that do it, have not been able
to
| determine if this is so yet, I searched webpages as well as the newsgroup
| archives but frustratingly I could not find the answer to what I would
have
| thought would be a common question.

I have one of these and AFAIK only Panasonic is using it. 'Genius' is their
trademark, inverter technology is not. It's a very powerful switchmode power
supply that varies the input power to the microwave. BTW, don't buy the
convection version - they are a swine to keep clean.

All other makes I know of cycle power to control cooking which does not work
as well for some items (oatmeal for one).

The sample I have drives both the magnetron high voltage and filament
from the same transformer. I would think this is hard on the magnetron
at moderate power where the filament isn't as hot as it should be but
perhaps it's not a big issue.

--- sam | Sci.Electronics.Repair FAQ Mirror: http://repairfaq.ece.drexel.edu/
Repair | Main Table of Contents: http://repairfaq.ece.drexel.edu/REPAIR/
+Lasers | Sam's Laser FAQ: http://repairfaq.ece.drexel.edu/sam/lasersam.htm
| Mirror Sites: http://repairfaq.ece.drexel.edu/REPAIR/F_mirror.html

Note: These links are hopefully temporary until we can sort out the excessive
traffic on Repairfaq.org.

Important: Anything sent to the email address in the message header is ignored.
To contact me, please use the Feedback Form in the FAQs.

Sam Goldwasser wrote in
:




The sample I have drives both the magnetron high voltage and filament
from the same transformer. I would think this is hard on the
magnetron at moderate power where the filament isn't as hot as it
should be but perhaps it's not a big issue.


lower filament voltage means longer tube life.
It would not be hard to include a regulated filament supply,though.

--
Jim Yanik
jyanik-at-kua.net

On 08 Dec 2004 19:23:31 -0500, Sam Goldwasser
wrote:


The sample I have drives both the magnetron high voltage and filament
from the same transformer. I would think this is hard on the magnetron
at moderate power where the filament isn't as hot as it should be but
perhaps it's not a big issue.



The best microwave design I've seen is an Amana from the late 70. It
has a separate filament transformer, so it can modulate the HV at
something like 1 Hz while keeping the filament hot. This is fast
enough to stop things from exploding/boiling over while the magnetron
is on. It's the only microwave I've had where the low power levels
were actually useful. It also has to be easier on the magnetron.
Andy Cuffe

"Andy Cuffe" wrote in message
...
On 08 Dec 2004 19:23:31 -0500, Sam Goldwasser
wrote:


The sample I have drives both the magnetron high voltage and filament
from the same transformer. I would think this is hard on the magnetron
at moderate power where the filament isn't as hot as it should be but
perhaps it's not a big issue.



The best microwave design I've seen is an Amana from the late 70. It
has a separate filament transformer, so it can modulate the HV at
something like 1 Hz while keeping the filament hot. This is fast
enough to stop things from exploding/boiling over while the magnetron
is on. It's the only microwave I've had where the low power levels
were actually useful. It also has to be easier on the magnetron.
Andy Cuffe


Those old Amanas were great, wouldn't mind having one now even, nice
stainless cavity, metal control panel, really slick.

"NSM" wrote in news:JkMtd.5013$Ya4.1618@edtnps84:



All other makes I know of cycle power to control cooking which does
not work as well for some items (oatmeal for one).

N



My 30 year old Sharp cooks my daily oatmeal just fine.

--
Jim Yanik
jyanik-at-kua.net

"Jim Yanik" . wrote in message
.. .

| "NSM" wrote in news:JkMtd.5013$Ya4.1618@edtnps84:
| All other makes I know of cycle power to control cooking which does
| not work as well for some items (oatmeal for one).

| My 30 year old Sharp cooks my daily oatmeal just fine.

So does my old 600W Toshiba, but my 1200W Sharp tends to explode it.

N

in article , wave at wave@waving wrote on 12/8/04 2:38
PM:

Have spent over 2 hours trying to find out if most or all microwaves do true
variable power output as opposed to the traditional cycling on & off to
attain different power levels, panasonic call this inverter technology, they
make it sound like they are the only ones that do it, have not been able to
determine if this is so yet, I searched webpages as well as the newsgroup
archives but frustratingly I could not find the answer to what I would have
thought would be a common question.


I was intrigued by this and other posts on the subject. Here is what I
conclude off the top of my head. I may be wrong in part. It sure is
difficult to glean specific information from the Panasonic web pages.

The inverter substitutes high frequency electronic switching and a SMALL
transformer for a much heavier magnetic transformer to provide the high
voltage necessary to operate a magnetron. The switching also allows varying
the voltage applied to the magnetron. In turn, that varies the magnetron's
output level. A conventional transformer's output voltage is not easily
changed. The down side is that efficency is reduced somewhat, especially at
low cooking level. That is, a larger fraction of the electrical power you
pay for ends up heating things other than food you are trying to heat.

Running transformers at high frequencies, what the inverter does, reduces
the size and weight required to handle large powers. The cost of electronic
devices such as transistors has dropped as manufacturing techniques
improved. Magnetic components such as transformers have not dropped much, if
any, in price. To a large extent, cost and size for these components vary
together.

Bill

"Repeating Rifle" wrote in message
...
| in article , wave at wave@waving wrote on 12/8/04
2:38

| I was intrigued by this and other posts on the subject. Here is what I
| conclude off the top of my head. I may be wrong in part. It sure is
| difficult to glean specific information from the Panasonic web pages.
....
| Running transformers at high frequencies, what the inverter does, reduces
| the size and weight required to handle large powers. The cost of
electronic
| devices such as transistors has dropped as manufacturing techniques
| improved. Magnetic components such as transformers have not dropped much,
if
| any, in price. To a large extent, cost and size for these components vary
| together.

Mine has a big ass inverter transformer wound with what looks like 1/4"
thick Litz wire (multiple strands to prevent surface effects).

N

in article XpNtd.5335$Ya4.1531@edtnps84, NSM at wrote on
12/8/04 4:57 PM:

Mine has a big ass inverter transformer wound with what looks like 1/4"
thick Litz wire (multiple strands to prevent surface effects).


1/4" litz seems crazy to me! A layer of litz 1/4" in diameter or thickness
made from finer litz would make more sense. How many turns are there of this
litz?

Bill

"Repeating Rifle" wrote in message
...
| in article XpNtd.5335$Ya4.1531@edtnps84, NSM at wrote on
| 12/8/04 4:57 PM:
|
| Mine has a big ass inverter transformer wound with what looks like 1/4"
| thick Litz wire (multiple strands to prevent surface effects).
|
|
| 1/4" litz seems crazy to me! A layer of litz 1/4" in diameter or thickness
| made from finer litz would make more sense. How many turns are there of
this
| litz?

It's not Litz wire, it's about 20# wire wound Litz fashion. It's two or
three layers and it looks like the primary? Actually 1/4 is a tad large, 1/8
might be closer, but I've never seen multiple strands used on a SMPS like
this.

N

in article %YRtd.7047$Ya4.4814@edtnps84, NSM at wrote on
12/8/04 10:07 PM:

It's not Litz wire, it's about 20# wire wound Litz fashion. It's two or
three layers and it looks like the primary? Actually 1/4 is a tad large, 1/8
might be closer, but I've never seen multiple strands used on a SMPS like
this.
Although it is not clear from you description, there are ways of winding
coils to minimize stry capaciatance.

Bill

"NSM" wrote in news:XpNtd.5335$Ya4.1531@edtnps84:


"Repeating Rifle" wrote in message
...
| in article , wave at wave@waving wrote on
| 12/8/04
2:38

| I was intrigued by this and other posts on the subject. Here is what
| I conclude off the top of my head. I may be wrong in part. It sure is
| difficult to glean specific information from the Panasonic web pages.
...
| Running transformers at high frequencies, what the inverter does,
| reduces the size and weight required to handle large powers. The cost
| of
electronic
| devices such as transistors has dropped as manufacturing techniques
| improved. Magnetic components such as transformers have not dropped
| much,
if
| any, in price. To a large extent, cost and size for these components
| vary together.

Mine has a big ass inverter transformer wound with what looks like
1/4" thick Litz wire (multiple strands to prevent surface effects).

N



"inverters" take rectified and filtered line AC(DC) and chop it at high
frequencies (multiple KHz,maybe 25-50 KHz) thru a non-iron(ferrite) core
transformer,then rectify and use for the magnetron supply.This requires a
inverter control PCB.

Ordinary iron core,low freq transformers run on 50/60 hz line AC.and weigh
a lot more than an inverter transformer.

--
Jim Yanik
jyanik-at-kua.net

"Jim Yanik" . wrote in message
.. .
| "NSM" wrote in news:XpNtd.5335$Ya4.1531@edtnps84:
....
| Mine has a big ass inverter transformer wound with what looks like
| 1/4" thick Litz wire (multiple strands to prevent surface effects).

| "inverters" take rectified and filtered line AC(DC) and chop it at high
| frequencies (multiple KHz,maybe 25-50 KHz) thru a non-iron(ferrite) core
| transformer,then rectify and use for the magnetron supply.This requires a
| inverter control PCB.
|
| Ordinary iron core,low freq transformers run on 50/60 hz line AC.and weigh
| a lot more than an inverter transformer.

Yes? What's your point? This Panasonic has the biggest ferrite inverter core
I've seen.

N

"NSM" wrote in news:154ud.36928$6f6.29966@edtnps89:


"Jim Yanik" . wrote in message
.. .
| "NSM" wrote in news:XpNtd.5335$Ya4.1531@edtnps84:
...
| Mine has a big ass inverter transformer wound with what looks like
| 1/4" thick Litz wire (multiple strands to prevent surface effects).

| "inverters" take rectified and filtered line AC(DC) and chop it at
| high frequencies (multiple KHz,maybe 25-50 KHz) thru a
| non-iron(ferrite) core transformer,then rectify and use for the
| magnetron supply.This requires a inverter control PCB.
|
| Ordinary iron core,low freq transformers run on 50/60 hz line AC.and
| weigh a lot more than an inverter transformer.

Yes? What's your point? This Panasonic has the biggest ferrite
inverter core I've seen.

N





I didn't know you had a Panasonic.(with inverter tech)

But for 1 KW power levels,of course you will have a large transformer.
Think how big (and heavy) a 1 KW+ iron-core xfmr would be.

--
Jim Yanik
jyanik-at-kua.net

Is 34 replies a record for this forum?

In article in nz.tech on Thu, 09
Dec 2004 00:52:43 GMT, Repeating Rifle says...
in article , wave at wave@waving wrote on 12/8/04 2:38
PM:

Have spent over 2 hours trying to find out if most or all microwaves do true
variable power output as opposed to the traditional cycling on & off to
attain different power levels, panasonic call this inverter technology, they
make it sound like they are the only ones that do it, have not been able to
determine if this is so yet, I searched webpages as well as the newsgroup
archives but frustratingly I could not find the answer to what I would have
thought would be a common question.


I was intrigued by this and other posts on the subject. Here is what I
conclude off the top of my head. I may be wrong in part. It sure is
difficult to glean specific information from the Panasonic web pages.

The inverter substitutes high frequency electronic switching and a SMALL
transformer for a much heavier magnetic transformer to provide the high
voltage necessary to operate a magnetron. The switching also allows varying
the voltage applied to the magnetron. In turn, that varies the magnetron's
output level. A conventional transformer's output voltage is not easily
changed. The down side is that efficency is reduced somewhat, especially at
low cooking level. That is, a larger fraction of the electrical power you
pay for ends up heating things other than food you are trying to heat.

Running transformers at high frequencies, what the inverter does, reduces
the size and weight required to handle large powers. The cost of electronic
devices such as transistors has dropped as manufacturing techniques
improved. Magnetic components such as transformers have not dropped much, if
any, in price. To a large extent, cost and size for these components vary
together.

This is how all switchmode supplies (like in your PC) work. Transformers
can be made much more efficient at the higher frequencies. It's probably
the reason why aircraft power runs at higher than ordinary mains
frequency.

"Adder" wrote in message
. nz...

| This is how all switchmode supplies (like in your PC) work. Transformers
| can be made much more efficient at the higher frequencies. It's probably
| the reason why aircraft power runs at higher than ordinary mains
| frequency.

Actually they ran 400 cycle for weight long before they came up with solid
state, let alone switchers.

N

In article ,
Adder wrote:

Transformers
can be made much more efficient at the higher frequencies. It's probably
the reason why aircraft power runs at higher than ordinary mains
frequency.

I heard that Tesla wanted mains frequencies to be around 300-400Hz for
this reason. I think the engineers who built the early power plants
(Edison?) felt this was impractical because they couldn't build big AC
generators that could spin that fast.

Wonder how things would be different if the situation could be revisited
today...

"Lawrence D¹Oliveiro" wrote in message
...
In article ,
Adder wrote:

Transformers
can be made much more efficient at the higher frequencies. It's probably
the reason why aircraft power runs at higher than ordinary mains
frequency.

I heard that Tesla wanted mains frequencies to be around 300-400Hz for
this reason. I think the engineers who built the early power plants
(Edison?) felt this was impractical because they couldn't build big AC
generators that could spin that fast.

Wonder how things would be different if the situation could be revisited
today...

Edison was a huge proponent of DC, IIRC Westinghouse was the main player in
the development of AC generation and transmission.

"Lawrence D¹Oliveiro" wrote in message
...

| I heard that Tesla wanted mains frequencies to be around 300-400Hz for
| this reason. I think the engineers who built the early power plants
| (Edison?) felt this was impractical because they couldn't build big AC
| generators that could spin that fast.

See the "War of the Currents" for more on Thomas Edison versus Nikola Tesla.
There were some Canadian and US systems (esp. powered from Niagara) that
used 25 cycle but it's pretty much all 50 or 60 Hz now. The higher the
frequency the lighter the magnetics but the greater the losses.

N

http://www.antiquewireless.org/otb/60cycles.htm

in article , Lawrence D¹Oliveiro at
_zealand wrote on 12/10/04 12:24 PM:

I heard that Tesla wanted mains frequencies to be around 300-400Hz for
this reason. I think the engineers who built the early power plants
(Edison?) felt this was impractical because they couldn't build big AC
generators that could spin that fast.

Wonder how things would be different if the situation could be revisited
today...

Very briefly, the commercial power frequency selected is a tradeoff between
costs of equipment and size of equipent. Core losses, from the iron in
transformers, increase with frequency. For 60 Hz ac, only about the outer
quarter inch of copper in cables is used. As frequency is increased, less of
the copper conductor is used. In the end 60 Hz is used for most European
power while 60 Hz was selected for the USA. In aircraft, weight can be much
more of an economic factor then efficiency. Thus 400 Hz is popular in
aircraft. But realize that only about 0.1 inch thickness of copper is
useful.

Bill

Sure you have your facts right Bill?

I understand the iron losses increasing, but why does copper cable 'only use
the outer quarter inch'?

My understanding is that this phenomena kicks in at much higher
frequencies - like above 50KHz.

Another factor in choosing the frequencies may have been to do with
audibility. I can imagine a (say) 800Hz transformer or motor making an
intolerable racket compared to a 50Hz model.

Regards

Ron
..
"Repeating Rifle" wrote in message
...
in article , Lawrence D¹Oliveiro
at
_zealand wrote on 12/10/04 12:24 PM:

I heard that Tesla wanted mains frequencies to be around 300-400Hz for
this reason. I think the engineers who built the early power plants
(Edison?) felt this was impractical because they couldn't build big AC
generators that could spin that fast.

Wonder how things would be different if the situation could be revisited
today...

Very briefly, the commercial power frequency selected is a tradeoff
between
costs of equipment and size of equipent. Core losses, from the iron in
transformers, increase with frequency. For 60 Hz ac, only about the outer
quarter inch of copper in cables is used. As frequency is increased, less
of
the copper conductor is used. In the end 60 Hz is used for most European
power while 60 Hz was selected for the USA. In aircraft, weight can be
much
more of an economic factor then efficiency. Thus 400 Hz is popular in
aircraft. But realize that only about 0.1 inch thickness of copper is
useful.

Bill

Thanks everyone for the advice, considering the advice I decided to not
worry about the inverter technology and bought a Sanyo microwave,
unfortunately there is no way I am going to fit this or any other microwave
in my microwave space without breaking the clearance rules laid out in the
manual, obviously a lot of people must ignore these, same goes to people who
build home kitchens as my kitchen as a space designed for microwaves but in
practice it will not do the job, bummer. I guess my question is if there is
a person who fixes microwaves or has some other reason to know what minimum
standard clearances are acceptable, i.e are the manufacturers clearances
over engineered? The manual for the sanyo says 20cm above, 10cm at the back
and 5cm on the sides.

"wave" wave@waving wrote in message ...
| Thanks everyone for the advice, considering the advice I decided to not
| worry about the inverter technology and bought a Sanyo microwave,
| unfortunately there is no way I am going to fit this or any other
microwave
| in my microwave space without breaking the clearance rules laid out in the
| manual, obviously a lot of people must ignore these, same goes to people
who
| build home kitchens as my kitchen as a space designed for microwaves but
in
| practice it will not do the job, bummer. I guess my question is if there
is
| a person who fixes microwaves or has some other reason to know what
minimum
| standard clearances are acceptable, i.e are the manufacturers clearances
| over engineered? The manual for the sanyo says 20cm above, 10cm at the
back
| and 5cm on the sides.

Unless it's a convection combo, 25mm all round is plenty. More is nice, but
what can you do?

N

"wave" wave@waving wrote in message ...
Thanks everyone for the advice, considering the advice I decided to not
worry about the inverter technology and bought a Sanyo microwave,
unfortunately there is no way I am going to fit this or any other
microwave
in my microwave space without breaking the clearance rules laid out in the
manual, obviously a lot of people must ignore these, same goes to people
who
build home kitchens as my kitchen as a space designed for microwaves but
in
practice it will not do the job, bummer. I guess my question is if there
is
a person who fixes microwaves or has some other reason to know what
minimum
standard clearances are acceptable, i.e are the manufacturers clearances
over engineered? The manual for the sanyo says 20cm above, 10cm at the
back
and 5cm on the sides.



Depends on the unit, note where the ventilation grills are and try to allow
some airflow, particularly to the fan. I've seen some installations that
used a small duct to a vent located above or below the oven.