[Milsurplus] AC Power on Ships

[Mike Morrow]

John wrote:

> I was just asked about the AC line on WW II era ships. It appears there is
> no neutral and the 115V 60 Hz just floats with each line 60-80 V AC above
> structure.
> 
> Is this correct and common or is there a fault?

Richard wrote:

>There is nothing wrong with an ungrounded ac system.  It has the
>advantage that you can continue to operate with the first ground fault,
>and the second will trip it off.  Also ground fault current (for the
>first fault) is limited by system capacitance to ground, and is small.
>For comparison, fault current on a grounded system is high, and any
>fault will trip it off.  Drop your screwdriver on the grounded system
>and you get a big flash and burn, with the ungrounded system it's merely
>a little spark.

Richard's explaination agrees with all the training information that
I ever saw as an engineering officer on a US Navy nuclear submarine.
It was a universally applied design concept on US Navy ships of all
classes and eras.

All power distribution floated above ground for reliability in the
presence of faults, including those that can develope from a salt-water
environment or from incident- or combat-inflicted damage.

Even three-phase 450 VAC (the highest voltage used in nuclear submarines
of my era) generation and distribution utilized ungrounded neutrals.

Mike / KK5F