[Milsurplus] 60 Hz.

[Dick]

Aircraft and military ships use 115 VAC 400 Hz, 3-phase power cuz it saves
weight for things like transformers, etc.  The cable reactance is nearly 
negligible
on aircraft because of the relatively short wire runs.  Basically, ditto for
shipboard 400 Hz power.

Check out MIL-STD-704.

Dick W1NMZ

----- Original Message ----- 
From: "Richard Brunner" <rbrunner at gis.net>
To: <Milsurplus at mailman.qth.net>
Sent: 20 June, 2005 03:22
Subject: Re: [Milsurplus] 60 Hz.


>
> Can anyone say why 60Hz was chosen?
>
> Several reasons:
> Machinery construction (motors, transformers) is most economical and 
> efficient at 50-60 cycles.  As the frequency goes up equipment gets 
> smaller requiring less iron and copper, but much over 60 cycles the iron 
> losses start increasing unreasonably.
>
> For power transmission the cable reactance becomes significant at higher 
> frequencies.
>
> 50-60 cycles was considered a reasonable compromise for incandescent light 
> flicker.  I have seen lights on a 25 cycle system, and light flicker is 
> very noticable.
>
> Low frequency (16 2/3, 25 cycles) is advantageous for traction motors, but 
> when it is rectified to use dc, or a cycloconverter (changing higher 
> frequency to lower frequency) is used, there is no advantage in low 
> frequency power.  Indeed, new systems use 50-60 cycle power distribution 
> for traction.
>
> Richard Brunner, AA1P