[Milsurplus] AC Power on Ships

[howard holden]

There is AC aboard the USS Ling, and it too is not grounded. A fair number of smaller electronics and electric stuff is AC operated, but there is also 115VDC for smaller MG sets, and interestingly, the interspace phone paging bells  run on 115VDC.

Howie WB2AWQ/7
  ----- Original Message ----- 
  From: Francesco Ledda<mailto:frledda at verizon.net> 
  To: jfor at quik.com<mailto:jfor at quik.com> ; 'Richard Brunner'<mailto:brunneraa1p at comcast.net> 
  Cc: milsurplus at mailman.qth.net<mailto:milsurplus at mailman.qth.net> 
  Sent: Sunday, October 24, 2010 6:14 PM
  Subject: Re: [Milsurplus] AC Power on Ships


  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>
  [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<mailto: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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