If the power companies increased the frequency of
AC mains current
from 60 Hz to something more like 1 kHz, would this make transformer
sizes smaller for AC equipment?

Besides older-style AC clocks no longer keeping correct time, what
would the downside to increased AC frequency be?

Michael

On Wed, 19 Mar 2008 09:25:13 -0700 (PDT),
m...@gmail.com wrote:

>If the power companies increased the frequency of AC mains current
>from 60 Hz to something more like 1 kHz, would this make transformer
>sizes smaller for AC equipment?
>
>Besides older-style AC clocks no longer keeping correct time, what
>would the downside to increased AC frequency be?
>
>Michael

The line frequency is already optimized, 50 or 60 Hz depending on some
tradeoffs.

Synchronous and induction motors would run at 60,000 RPM.

Transformers would scream.

Skin loss would go way up on transmission lines.

Generation would be difficult.

John

 (m...@gmail.com) writes:
> If the power companies increased the frequency of AC mains current
> from 60 Hz to something more like 1 kHz, would this make transformer
> sizes smaller for AC equipment?
> 
> Besides older-style AC clocks no longer keeping correct time, what
> would the downside to increased AC frequency be?
> 
> Michael

The transmission of the signals would probably be lossier, and of course
there'd be more radiation of the signal (to cause interference) since the
wiring would be more efficient at radiating the signal at higher frequencies.

You don't have to cook up such a scenario to get an answer.

Years ago, and presumably still, aircraft (and I think some ships) used
400Hz AC so the transformers would be smaller.

And any switching supply rectifies the AC line directly, turns it into
a comparatively high frequency, so the transformer that actually does
the voltage conversion can be smaller.

It would never happen, unles someone was completely starting from scratch
in some isolated spot.  The changeover, ie the replacement of everything,
would be too costly.

  Micahel

On 3/19/08 9:25 AM, in article
4...@e6g2000prf.googlegroups.com,
"m...@gmail.com" <m...@gmail.com> wrote:

> If the power companies increased the frequency of AC mains current
> from 60 Hz to something more like 1 kHz, would this make transformer
> sizes smaller for AC equipment?
> 
> Besides older-style AC clocks no longer keeping correct time, what
> would the downside to increased AC frequency be?
> 
> Michael

Primarily higher line losses caused by higher current.

<m...@gmail.com> wrote in message 
news:4...@e6g2000prf.googlegroups.com...
> If the power companies increased the frequency of AC mains current
> from 60 Hz to something more like 1 kHz, would this make transformer
> sizes smaller for AC equipment?
>
> Besides older-style AC clocks no longer keeping correct time, what
> would the downside to increased AC frequency be?
>
> Michael

A better idea might be to use DC for distribution, as is already done for 
high voltage long haul transmission. I think losses are about 1/2 of what 
they are for 60 Hz AC. Each household could have, essentially, a motor 
drive type inverter for any AC only electronics. But many appliances are 
now using small three phase induction motors with their own little V/F 
inverters, and the first thing they do is convert the AC line to DC. 
Computers and other similar electronics will happily run on 150 VDC. Such a 
system would also work well for battery backup.

There are safety issues with DC, but actually 50/60 Hz AC is a dangerous 
frequency because it causes fibrillation. DC basically makes your muscles 
contract so you can't let go.

Paul 

"Paul E. Schoen =  mind numbingly stupid ASS"


> A better idea might be to use DC for distribution, as is already done for 
> high voltage long haul transmission. I think losses are about 1/2 of what 
> they are for 60 Hz AC. Each household could have, essentially, a motor 
> drive type inverter for any AC only electronics.


**  Straight back to the 1920's.

 Everything the Schoen ASS says is dangerous, stupid and WRONG.

Hee, haw, hee haw, hee haw .......


......  Phil

Phil Allison wrote:
> 
> Hee, haw, hee haw, hee haw .......


   There's a new donkey in town. :(


-- 
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On Mar 20, 3:44 am, et...@FreeNet.Carleton.CA
(Michael Black) wrote:
>  (mrdarr...@gmail.com) writes:
> > If the power companies increased the frequency of AC mains current
> > from 60 Hz to something more like 1 kHz, would this make transformer
> > sizes smaller for AC equipment?
>
> > Besides older-style AC clocks no longer keeping correct time, what
> > would the downside to increased AC frequency be?
>
> > Michael
>
> The transmission of the signals would probably be lossier, and of course
> there'd be more radiation of the signal (to cause interference) since the
> wiring would be more efficient at radiating the signal at higher frequencies.
>
> You don't have to cook up such a scenario to get an answer.
>
> Years ago, and presumably still, aircraft (and I think some ships) used
> 400Hz AC so the transformers would be smaller.
>
> And any switching supply rectifies the AC line directly, turns it into
> a comparatively high frequency, so the transformer that actually does
> the voltage conversion can be smaller.
>
> It would never happen, unles someone was completely starting from scratch
> in some isolated spot.  The changeover, ie the replacement of everything,
> would be too costly.
>
>   Micahel

Speaking of isolated systems...

I've worked on marine seismic survey gear that uses 2KHz for power
distribution along the up to 10km line lengths used. The driver being
the smaller transformer sizes required when you have to fit stuff into
70mm diameter cables.

But similar competing systems also use DC for distribution, and I've
worked on the specification and design of a 10km+ system that used
600V DC for distribution. Due to voltage drop you could get less than
100V at the tail end of the system, so the DC-DC converter had to be
designed for a 70V-600V input span.

Dave.

"David L. Jones" <a...@gmail.com> wrote in message
news:d...@s19g2000prg.googlegroups.com...
> On Mar 20, 3:44 am, et...@FreeNet.Carleton.CA (Michael Black) wrote:
> >  (mrdarr...@gmail.com) writes:
> > > If the power companies increased the frequency of AC mains current
> > > from 60 Hz to something more like 1 kHz, would this make transformer
> > > sizes smaller for AC equipment?
> >
> > > Besides older-style AC clocks no longer keeping correct time, what
> > > would the downside to increased AC frequency be?
> >
> > > Michael
> >
> > The transmission of the signals would probably be lossier, and of course
> > there'd be more radiation of the signal (to cause interference) since
the
> > wiring would be more efficient at radiating the signal at higher
frequencies.
> >
> > You don't have to cook up such a scenario to get an answer.
> >
> > Years ago, and presumably still, aircraft (and I think some ships) used
> > 400Hz AC so the transformers would be smaller.
> >
> > And any switching supply rectifies the AC line directly, turns it into
> > a comparatively high frequency, so the transformer that actually does
> > the voltage conversion can be smaller.
> >
> > It would never happen, unles someone was completely starting from
scratch
> > in some isolated spot.  The changeover, ie the replacement of
everything,
> > would be too costly.
> >
> >   Micahel
>
> Speaking of isolated systems...
>
> I've worked on marine seismic survey gear that uses 2KHz for power
> distribution along the up to 10km line lengths used. The driver being
> the smaller transformer sizes required when you have to fit stuff into
> 70mm diameter cables.
>
> But similar competing systems also use DC for distribution, and I've
> worked on the specification and design of a 10km+ system that used
> 600V DC for distribution. Due to voltage drop you could get less than
> 100V at the tail end of the system, so the DC-DC converter had to be
> designed for a 70V-600V input span.
>
> Dave.

What? What the hell kind of a system would drop 83% of it's voltage in the
line? That makes zero sense. If the DC line losses are so great then the
voltage must be higher to keep the current at a reasonable level.

The best way is a plus and minus DC system then the insulation requirements
are about 2.8 times less than that required for an AC system of similar
voltage.  Voltage handling in the switches and electronics is 1/2 of the
actual voltage on the line. Furthermore there are no skin effect
considerations or inductive or capacitive loses in the line. Conversion at
either end can be at high frequencies, 20kHz or higher keeping the magnetics
very small and compact.

m...@gmail.com wrote:
>If the power companies increased the frequency of AC mains current
>from 60 Hz to something more like 1 kHz, would this make transformer
>sizes smaller for AC equipment?

>Besides older-style AC clocks no longer keeping correct time, what
>would the downside to increased AC frequency be?

Some airplane/submarine systems are supposedly 400 Hz AC, which let's you
have smaller transformers at the price of less efficiency (asfaik) and more
electromagnetic interference.
Also skineffect comes into play and increase losses with higher frequency.

However there might be a more optimal frequency between 60 - 400 Hz.
(any suggestion?)

For the last distribution step (less than 1200V) it might be useful with 
DC distribution due efficient SMPS. And that many appliancies anyway will
make DC of the mains as a first step.

Still even if you would start from scratch on an isolated island. The cost
to order/special manufacture equipment for an odd mains type can be 
prohibitive. The only exception being equipment that rectify anyway.