[Milsurplus] AC Power on Ships

[Francesco Ledda]

They probably don't want current returns to the ship steel to avoid
corrosion.

-----Original Message-----
From: milsurplus-bounces at mailman.qth.net
[mailto:milsurplus-bounces at mailman.qth.net] On Behalf Of J. Forster
Sent: Sunday, October 24, 2010 7:38 PM
To: Richard Brunner
Cc: milsurplus at mailman.qth.net
Subject: Re: [Milsurplus] AC Power on Ships

The radio spaces (at least) on the BB-59 (Massachusetts) have floating AC.
I think there may be a nearby MG set.

The question came up in connection with a blown EMI filter a C-L-C Pi
network.

Thank you,

-John

==============



> First, all the WWII ships I have seen were DC, nominally 110-120
> volts.
>
> 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, AA1P
>
> On Sun, 2010-10-24 at 15:18 -0700, J. Forster wrote:
>> Hi,
>>
>> 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?
>>
>> And, more importantly why would they do it this way?
>>
>> Best,
>>
>> -John
>
>
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