[GreenKeys] Secret DC Basement in NYC - Great History

[Bruce Gentry]

I have read about ships using 100-120 volts DC for radio equipment, 
motor generators or dynamotors provided high voltage for the 
transmitters. Supposedly this was to allow  for easy battery backup.  I 
think the power on Liberty ships was all DC, I don't know about 
destroyers or escort carriers. The Titanic was DC, the Queen Mary was as 
well, probably still using some or all of the DC system until the ship 
was taken out of service.  The utility here in Syracuse provided DC from 
a central power station until 1953. They had to install hundreds of 
motor generator sets for elevators and theatrical arc lamps throughout 
the city, I believe I shut off and tore out  the last one  powering an 
elevator  in the city in the late 1990s.  There are still hundreds of 
elevators in Syracuse  that use MG sets powered by the AC line for 
variable voltage control. Because of the strong third harmonics typical 
single phase computer switching power supplies generate in a 3 phase 
four wire power system, there are a growing number of  buildings or even 
neighborhoods where modern DC substations are once again becoming 
common. It is fairly easy to convert three phase AC to DC efficiently in 
one local substation to operate massive numbers of computers while 
generating very little third harmonic energy.  A surprising number of 
computers can be connected to 320-380 volts DC with only minor  
modifications because their switching power supplies already produce 
that voltage by rectifying and/or doubling the peak power line voltage.


      Bruce Gentry, KA2IVY

On 5/12/15 4:53 PM, David Christ wrote:
> Someone else on the list should be able to confirm this, but ships during and prior to WW II and even more recently ran on DC (220 V?).  The high voltage for the tubes was provided by motor generator sets.  And of course many of us recall the dynamotors used in many mobile two-way radios used by police and taxis.
>
> David K0LUM
>
>
> On May 12, 2015, at 2:31 PM, Jim Haynes <jhhaynes at earthlink.net> wrote:
>
>> If you lived in a DC powered area of a city it was hard to build a ham
>> transmitter of any power because you needed a motor-generator set to
>> develop the high voltage DC for the amplifier tubes.
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