The electrical plant follows conventional German submarine practice with storage batteries, main electric machines usable as either motors or generators, electrically operated auxiliaries and accompanying controls and distribution systems.  In general, most equipments are compact and designed to be accessible for maintenance, although in some cases the location in the vessel interfered with accessibility.  Greater temperature rises appear to be permitted then is current USN practice.  Efforts to conserve copper and other critical materials were evidenced.  
March, 1946
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A. Descriptive
  (a) Introduction
  (b) Description
  (c) Conclusions
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C  O  N  F  I  D  E  N  T  I  A  L
  A.  Descriptive  
          (a)  Introduction  
          This report of the electrical system is written to present in a general way the type of system installed, its employment, and methods of distribution as well as some of the characteristics of the auxiliary power equipment.  For detailed information regarding these components reference should be made to the applicable detail reports.  
          (b)  Description  
          This type of vessel is provided with two main double armature electric machines, one port and one starboard, which can be mechanically and electrically connected for use either as motors for the ship's propulsion or for use as generators for charging the batteries.  
          Split main cubicles are installed, one port and one starboard, for the control of the main power.  These cubicles can be isolated from the batteries by means of double pole air circuit breakers.  
          Two batteries are provided, one forward (No. 2) and one aft (No. 1).  These are German type 44MAL740 each consisting of 62 cells.  The cells are of the pasted plate type designed for a "life" of 15 to 21 months.  Neither individual cell voltmeters nor hydrogen detectors are installed.  Switching arrangements provide for use of the batteries individually, in series, or in parallel.  Voltage variations between 110 to 170 and 220 to 340 are possible.  
          Auxiliary power requirements can be selected from either battery or can be divided between both batteries.  Auxiliary machinery operates from voltages of 110 to 170.  Two auxiliary power switchboards are provided on which the auxiliary machinery circuits are connected.  Individual circuit switches are not generally provided on these boards, the circuits being fused only.  
          Regulated 110 V DC for purposes listed below is obtained through the use of voltage sensitive relay actuated regulators.  
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          (1)  Ship's Illumination.  
          (2)  Dial Light Illumination.  
          (3)  I.C. Transmitter-Indicator Systems.  
          (4)  I.C. Hull Opening & Vent Valve Indicating Systems.  
          (5)  Control Circuits for Motor Generators.  
          (6)  Electronic Equipments as required.  
          (7)  Standby Torpedo Charging Power Supply.  
          (8)  Running & Signal Lights.  
          Controllers for motors and motor generators are generally located adjacent to the unit to be controlled.  Manual starters are used in most applications.  These provide for across the line starting, resistance starting and for starting series field connected windings.  Magnetic controllers are only employed for motor generators, steering and hydraulic pump motors.  
          Interior Communication Circuits, Fire Control Circuits and A.C. motor generator control circuits are not grouped to be controlled from common switchboards as is generally done in USN practice.  
          A common fused board located in the Radio Room provides for the distribution of A.C. power and 110 V. regulated D.C. power for the electronic equipment.  The A.C. power requirements are not as great in this system primarily because most I.C. equipment is designed to operated on 110 Volt D.C. and the electronic installation is not as extensive as in present USN submarines.  
          Cable and lead designations in the form of cable tags and stamped terminals or fibre tags are not as widely used or required as in present USN practice.  See report 2G-9C-S28 for detailed information.  
          Practically all cable is provided with synthetic rubber insulation around which is woven a protective metal covering.  For a given cross section current densities are generally greater than is present in USN practice.  
          Common stuffing boxes are used for cable banks passing through water-tight bulkheads, as many as forty to fifty cables including main power cables are led through one stuffing box.  
          Methods employed for supporting cable banks and cable entrances to equipments are somewhat similar to methods currently being used on USN submarines.  Circular rubber packing of rectangular cross section not  
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  vulcanized to the cable is used in tube terminals and stuffing tubes.  
          Captive screws are used extensively on covers, subassemblies, and other components in all systems.  
          The trend of German design particularly in I.C., F.C. and electronic equipment is to have the components of the various equipments so constructed that they may be readily removed for replacement or maintenance without disconnecting the system wiring.  Considerable emphasis is placed on designs that minimize the possibility of incorrect assembly.  
          In general, electrical clearances and insulation are considered as being inferior to present USN requirements.  
          The design contemplates use of electrical energy for the following purposes:  
                  a.  Submerged propulsion, except when snorkeling  
                  b.  Surface propulsion in emergency  
                  c.  Steering and depth control  
                  d.  Ship's heating and ventilating  
                  e.  All pumps excepting fresh water  
                  f.  Fresh water stills  
                  g.  Torpedo heating and charging  
                  h.  Galley equipment  
                  i.  Galley refrigerator  
                  j.  Motor generators to provide A.C. power for various purposes  
                  k.  Air compressor (Note there is in addition a Diesel air compressor installed)  
                  l.  Ship's lighting  
                  m.  Interior communication equipments  
                  n.  Signalling and indicating systems, telegraphs, and gyro compass  
          (c)  Conclusions  
          The overall design of the electric plant installed in this type vessel reflected the German need to conserve labor and material and additionally to have systems and methods that were readily adaptable for mass production of submarines to an extent that only the barest essentials with regard to present USN operating doctrine are incorporated in his systems, thus placing increased responsibility upon operating personnel for the successful operation of these plants.  
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          The above considerations required the acceptance of practices in design and installations not presently acceptable to USN designers.  
          The simplicity of the installations and the German method of presentation is such that operating personnel can readily become acquainted with all phases of the installation.  
          Interrogation of USN personnel who operated and are operating this type electrical installation indicates that electrical maintenance is negligible and that the equipments operate satisfactorily.  
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