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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 DčOliveiro" 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 |
"Lawrence DčOliveiro" 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 |
I thought large aircraft almost universally used 400hz? What a Lancaster Bomber, this is the Planes I am on about I don't know anything about Lancaster bombers, that's why I asked the question. |
Is 34 replies a record for this forum?
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in article , Lawrence DčOliveiro 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 |
in article , Adder at wrote
on 12/10/04 2:14 PM: Multipole generators can do this, maybe they had not heard of more than 2? poles back then I must admit that I do not know for sure, but multipole alternators probably came before the electrification of Niagra. Hydraulic turbines could not spin at synchronous speed. The trouble with multipole alternators is that they will be larger. Because they turn slowly, they require more torque for the ame amount of power and, therefore, must be built more ruggedly. Bill |
"Repeating Rifle" wrote in message ... | I must admit that I do not know for sure, but multipole alternators probably | came before the electrification of Niagra. Hydraulic turbines could not spin | at synchronous speed. | | The trouble with multipole alternators is that they will be larger. Because | they turn slowly, they require more torque for the ame amount of power and, | therefore, must be built more ruggedly. http://www.antiquewireless.org/otb/60cycles.htm N |
"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. |
In article IUuud.17248$U47.1533@clgrps12, "NSM"
wrote: http://www.antiquewireless.org/otb/60cycles.htm Typical US-centric--no mention of 50Hz. |
"Lawrence DčOliveiro" wrote in message ... In article IUuud.17248$U47.1533@clgrps12, "NSM" wrote: http://www.antiquewireless.org/otb/60cycles.htm Typical US-centric--no mention of 50Hz. Not just US, but all of North America, that's probably where it was written, hard to blame them. The story on 50Hz is pretty similar I'm sure. |
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 DčOliveiro 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 |
On Sun, 12 Dec 2004 02:37:17 GMT Repeating Rifle
wrote: Most applications have wire smaller than 1/4" For example, #10 wire, by eyeball, is about 1/10". And that is diameter. This skin effect is what limits the effective size of the conductor. You're correct, at the consumer's end, but I believe the concern over losses was more for the power transmission lines. At 60 Hz, the skin depth is about 1 cm (~3/8") so this is already a factor with 4/0 cable. Inside your home it's irrelevant. I suspect that for long distance transmission lines the stranding is often a mix of plated steel on the inside for strength and copper on the outside for conductivity. The skin depth makes that a reasonable choice. - ----------------------------------------------- Jim Adney Madison, WI 53711 USA ----------------------------------------------- |
"Jim Adney" wrote in message ... .... | I suspect that for long distance transmission lines the stranding is | often a mix of plated steel on the inside for strength and copper on | the outside for conductivity. The skin depth makes that a reasonable | choice. .... Aluminium is often the choice. Also I heard once that some cables use a low Curie point coating which increases in resistance and heat loss below a certain point melting off any ice build up. N |
NSM wrote:
"Jim Adney" wrote in message .. . ... | I suspect that for long distance transmission lines the stranding is | often a mix of plated steel on the inside for strength and copper on | the outside for conductivity. The skin depth makes that a reasonable | choice. ... Aluminium is often the choice. Also I heard once that some cables use a low Curie point coating which increases in resistance and heat loss below a certain point melting off any ice build up. N I have seen pieces of power cable for transmission lines that was hollow. Bill K7NOM |
On Sun, 12 Dec 2004 04:54:58 GMT "NSM" wrote:
Also I heard once that some cables use a low Curie point coating which increases in resistance and heat loss below a certain point melting off any ice build up. Interesting idea, but the Curie point affects ferromagnetism, not resistance, and the material would have to be iron based. I wonder if there are any ferromagnetic materials which have Curie points below 0C? I'm not familiar with the range of possiblities, but the examples I know of are all in the few hundreds of degrees C. If the temp dropped below the Curie point and an iron cable suddenly became ferromagnetic again, would that decrease the skin depth? If so, this would work as you say. Interesting question. I'm going to have to ask someone else about this.... ;-) - ----------------------------------------------- Jim Adney Madison, WI 53711 USA ----------------------------------------------- |
On Sun, 12 Dec 2004 17:08:58 GMT Bill Janssen
wrote: I have seen pieces of power cable for transmission lines that was hollow. What did they do to keep the stranding from collapsing inward? - ----------------------------------------------- Jim Adney Madison, WI 53711 USA ----------------------------------------------- |
Jim Adney wrote:
On Sun, 12 Dec 2004 17:08:58 GMT Bill Janssen wrote: I have seen pieces of power cable for transmission lines that was hollow. What did they do to keep the stranding from collapsing inward? - ----------------------------------------------- Jim Adney Madison, WI 53711 USA ----------------------------------------------- The strands were ribbon shaped and the edges were a locking "tongue and grove" arrangement. I do not know how it was assembled but the individual strands could slide, making it fairly flexible. The piece I saw could be disassembled and re-assembled. I read of one power company that pulled fiber optic cable inside their power line. That optic cable was for communications, not power :-) Bill K7NOM |
In article ,
Jim Adney wrote: On Sun, 12 Dec 2004 17:08:58 GMT Bill Janssen wrote: I have seen pieces of power cable for transmission lines that was hollow. What did they do to keep the stranding from collapsing inward? Why should it collapse inward? |
On Tue, 14 Dec 2004 15:54:57 +1300 Lawrence D'Oliveiro
wrote: In article , Jim Adney wrote: On Sun, 12 Dec 2004 17:08:58 GMT Bill Janssen wrote: I have seen pieces of power cable for transmission lines that was hollow. What did they do to keep the stranding from collapsing inward? Why should it collapse inward? Murphy's Law, perhaps? A hollow circular arrangement, even helical, would only be an unstable equilibrium. Any perturbation would cause it to collapse. - ----------------------------------------------- Jim Adney Madison, WI 53711 USA ----------------------------------------------- |
On Tue, 14 Dec 2004 00:20:17 GMT Bill Janssen
wrote: The strands were ribbon shaped and the edges were a locking "tongue and grove" arrangement. I do not know how it was assembled but the individual strands could slide, making it fairly flexible. The piece I saw could be disassembled and re-assembled. What kind of size are we talking about here? Approx how many strands in a layer, how many layers? I'm just curious about the scale. I read of one power company that pulled fiber optic cable inside their power line. That optic cable was for communications, not power :-) ;-) - ----------------------------------------------- Jim Adney Madison, WI 53711 USA ----------------------------------------------- |
A hollow circular arrangement, even helical, would only be an unstable
equilibrium. Any perturbation would cause it to collapse. What if each strand was keystone shaped? |
I have just bought a new sanyo EMS665W microwave and have just noticed that
the microwave door has no rubberlike seal on it, the hard plastic on the inside of the door mates with the metal of the oven enclosure, there is no sealing material at all. Anyhow obviously I am a bit concerned as I have never seen this before and they have always said how important it is for the door seal to be in good condition to prevent leaks so what gives with an oven that has no seal at all? Has anybody seen this on other makes and models? http://www.sanyo.co.nz/ |
"wave" wave@waving wrote in message ... | I have just bought a new sanyo EMS665W microwave and have just noticed that | the microwave door has no rubberlike seal on it, the hard plastic on the | inside of the door mates with the metal of the oven enclosure, there is no | sealing material at all. Anyhow obviously I am a bit concerned as I have | never seen this before and they have always said how important it is for the | door seal to be in good condition to prevent leaks so what gives with an | oven that has no seal at all? Has anybody seen this on other makes and | models? I've never seen such a seal and it wouldn't stop microwaves in any case. My microwave - Sharp - is the same setup as yours. N |
NSM wrote:
I've never seen such a seal and it wouldn't stop microwaves in any case. My microwave - Sharp - is the same setup as yours. No seal on my Mitsubishi microwave either. -- EMB |
"NSM" wrote in message news:l%owd.82367$6f6.51787@edtnps89... "wave" wave@waving wrote in message ... | I have just bought a new sanyo EMS665W microwave and have just noticed that | the microwave door has no rubberlike seal on it, the hard plastic on the | inside of the door mates with the metal of the oven enclosure, there is no | sealing material at all. Anyhow obviously I am a bit concerned as I have | never seen this before and they have always said how important it is for the | door seal to be in good condition to prevent leaks so what gives with an | oven that has no seal at all? Has anybody seen this on other makes and | models? I've never seen such a seal and it wouldn't stop microwaves in any case. My microwave - Sharp - is the same setup as yours. N I was talking about the brown hard rubber like material on the inside of the door which I think use to be in all microwaves, certainly all the ones I ever seen. |
wave wrote:
How new is your microwave, I know sanyo still had them about 4 years ago but maybe no microwave ovens have them anymore for some reason. 5 years old or so, maybe a little more. I also just checked the one in my motorhome (2 year old Sanyo) and it's seal-less too. -- EMB |
"EMB" wrote in message ... wave wrote: How new is your microwave, I know sanyo still had them about 4 years ago but maybe no microwave ovens have them anymore for some reason. 5 years old or so, maybe a little more. I also just checked the one in my motorhome (2 year old Sanyo) and it's seal-less too. -- EMB Oh well, obviously I have nothing to worry about, thanks. |
In article , "wave" wave@waving wrote:
I was talking about the brown hard rubber like material on the inside of the door which I think use to be in all microwaves, certainly all the ones I ever seen. Rubber isn't going to stop microwaves, is it? |
In article ,
Jim Adney wrote: On Tue, 14 Dec 2004 15:54:57 +1300 Lawrence D'Oliveiro wrote: In article , Jim Adney wrote: On Sun, 12 Dec 2004 17:08:58 GMT Bill Janssen wrote: I have seen pieces of power cable for transmission lines that was hollow. What did they do to keep the stranding from collapsing inward? Why should it collapse inward? Murphy's Law, perhaps? A hollow circular arrangement, even helical, would only be an unstable equilibrium. Any perturbation would cause it to collapse. Tell that to your water pipes, your chimney, tubular car chassis members, and all kinds of other hollow building components where strength and lightness are both required. |
wave wrote:
"EMB" wrote in message ... wave wrote: How new is your microwave, I know sanyo still had them about 4 years ago but maybe no microwave ovens have them anymore for some reason. 5 years old or so, maybe a little more. I also just checked the one in my motorhome (2 year old Sanyo) and it's seal-less too. -- EMB Oh well, obviously I have nothing to worry about, thanks. If you are a little aprehensive you can buy a checker. |
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 |
On Fri, 17 Dec 2004 22:10:35 +1300, Adder wrote in
.nz: In article in nz.tech on Fri, 17 Dec 2004 10:51:37 +1300, wave wave@waving says... I have just bought a new sanyo EMS665W microwave and have just noticed that the microwave door has no rubberlike seal on it, the hard plastic on the inside of the door mates with the metal of the oven enclosure, there is no sealing material at all. Anyhow obviously I am a bit concerned as I have never seen this before and they have always said how important it is for the door seal to be in good condition to prevent leaks so what gives with an oven that has no seal at all? Has anybody seen this on other makes and models? perhaps you have noticed that you microwave oven door contains shock horror glass through which microwaves can pass provided the gap between the door and chassis is small it will be safe Please explain to us the difference between ordinary glass and shock horror glass? -- Regards, Nicolaas. |
"Bill Janssen" wrote in message ... Adder wrote: .... The microwave seal on a "Microwave" is there, you just can't see it. A gap with a length of 1 /4 wave is a short for microwave. The length can be different if loaded with a dielectric. Bill k7NOM The OP was asking about a rubber seal and if it stopped microwaves. N |
"Alan Harriman" wrote in message ... | | 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 Actually a microwave does an excellent job. The sensor ones do it automatically. N |
On Fri, 17 Dec 2004 17:48:34 +1300, Lawrence DčOliveiro
put finger to keyboard and composed: In article , "wave" wave@waving wrote: I was talking about the brown hard rubber like material on the inside of the door which I think use to be in all microwaves, certainly all the ones I ever seen. Rubber isn't going to stop microwaves, is it? Wouldn't a rubber seal exacerbate leakage issues? I mean, wouldn't it effectively *create* a gap through which microwaves could leak? - Franc Zabkar -- Please remove one 's' from my address when replying by email. |
"Nicolaas Hawkins" wrote in message ... | perhaps you have noticed that you microwave oven door contains shock | horror glass through which microwaves can pass | Please explain to us the difference between ordinary glass and shock | horror glass? Like the difference between John McCain and George Bush? N |
"Frank" wrote in message ... | On Fri, 17 Dec 2004 16:36:00 GMT, Bill Janssen wrote: | PLEASE DO NOT POST IN USENET GROUPS WITH HTML ITS A BIG NO NO.. It's mildly annoying unless it is done for a purpose but nowhere near as annoying as SHOUTING. N |
"Allodoxaphobia" wrote in message ... | No steenkin' "rubber" seal on my 20 year old Monkey Ward microwave. | | Jonesy Have we beaten this subject to death yet or would the other 100 million microwave owners like to chip in? N |
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