Date: Thu, 17 Mar 2016 14:59:11 +0000
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From: phl@netikka.fi
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Subject: Re: LF: 33 Hz QRM
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Hello John, Johan, LF

16 2/3 Hz should probably be 16 1/3 Hz, one third of 50 Hz as John  
pointed out.


Here in OH-land we use 50 Hz for the railways but during my EE  
studies, the SM-land railway QRG was also mentioned for two reasons  
(hope I remember this right now, it was about 25 years ago...):

- A lower frequency was selected to minimize the voltage drop caused  
by the series inductance formed by the long overhead lines supplying  
the locomotive.

- Initially 16 1/3 Hz was generated in rotary converters, for example  
a 6-pole 50 Hz motor would drive a two pole generator which gives the  
required step-down. Rotary converters need maintenance and so this  
system was later replaced by non-mechanical devices such as  
cyclo-converters or other early ways of electronic frequency  
converters that supposedly require less maintenance. In fact,  I think  
this was the main reason for bringing up this subject in school.


BR

Paul-Henrik, OH1LSQ


Quoting Andy Talbot <andy.g4jnt@gmail.com>:

> Is that to minimise skin loss in steel track ?
>
> UK Third rail is, of course, DC, and I once spent an idle moment
> calculating the loss if 50Hz AC were to be used with magnetic iron
> conductors.  I think I came to the conclusion a 1MW train could probably
> travel a few hundred metres before it lost its power supply.
>
> andy  G4JNT
>
> On 17 March 2016 at 13:21, Johan Bodin <jhbodin@tele2.se> wrote:
>
>> Railway QRG is 16 2/3 Hz in Sweden too.
>>
>> 73 de Johan SM6LKM
>>
>> John Rabson wrote:
>>
>>> I seem to recall that some railway systems use at about 16 2/3 Hz (one
>>> third of 50 Hz) for traction.
>>>
>> ...
>>
>>> Can someone say whether my recollections are correct, please?
>>>
>>> 73 John F5VLF
>>>
>>
>>