Cooking Equipment (rec.food.equipment) Discussion of food-related equipment. Includes items used in food preparation and storage, including major and minor appliances, gadgets and utensils, infrastructure, and food- and recipe-related software.

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  #43 (permalink)   Report Post  
NSM
 
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"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


  #44 (permalink)   Report Post  
NSM
 
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"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


  #45 (permalink)   Report Post  
James Sweet
 
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"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.




  #46 (permalink)   Report Post  
James Sweet
 
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"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.


  #47 (permalink)   Report Post  
Lawrence DčOliveiro
 
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In article <IUuud.17248$U47.1533@clgrps12>, "NSM" >
wrote:

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


Typical US-centric--no mention of 50Hz.
  #48 (permalink)   Report Post  
Lawrence DčOliveiro
 
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In article <IUuud.17248$U47.1533@clgrps12>, "NSM" >
wrote:

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


Typical US-centric--no mention of 50Hz.
  #49 (permalink)   Report Post  
James Sweet
 
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"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.


  #50 (permalink)   Report Post  
James Sweet
 
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"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.




  #51 (permalink)   Report Post  
Ron McNulty
 
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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
>



  #52 (permalink)   Report Post  
Ron McNulty
 
Posts: n/a
Default

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
>



  #53 (permalink)   Report Post  
Jim Adney
 
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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
-----------------------------------------------
  #54 (permalink)   Report Post  
Jim Adney
 
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Default

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
-----------------------------------------------
  #55 (permalink)   Report Post  
Jim Adney
 
Posts: n/a
Default

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
-----------------------------------------------
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