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2
MAIN GENERATORS AND MOTORS
AND AUXILIARY GENERATOR
 
A. PROPULSION
 
2A1. Description. The propellers of a modern submarine are driven by four main motors (see Figure 2-1.) arranged in pairs to drive each propeller shaft through a reduction gear, or by two double armature main motors which are coupled directly to and operate in the speed range of the propellers.

Each gear unit used in a gear drive installation is a single reduction, double helical type designed to reduce the main motor speed of approximately 1300 revolutions per minute (rpm) to the propeller speed of 280 rpm.

Power for driving the main motors is obtained from one of two sources: the four main generators driven by the main diesel engines; or, for submerged operation, the main storage batteries.

A single main generator, or any combination of the four, may be employed for charging the main storage, batteries.

The auxiliary generator, driven by the auxiliary diesel engine, serves several purposes. It supplies current 1) for all auxiliary circuits, relieving the battery of the auxiliary load; 2) for charging the batteries at a low rate; and 3) for driving the main motors at slow speed through the main storage batteries.

  Control of main propulsion machinery is accomplished through the main propulsion control equipment, or control cubicle, located in the maneuvering room.

Detailed descriptions and instructions for the care and maintenance of the various components and their related controls are given in the chapter dealing with each specific component.

2A2. Manufacturers of main propulsion equipment. Main motors, main generators, and auxiliary generators are produced for and furnished to the Navy by the following manufacturers: General Electric, Allis-Chalmers, Elliott, and Westinghouse.

Main control cubicles are manufactured by General Electric, Cutler-Hammer, and Westinghouse. Installations are usually paired as follows: General Electric motors, generators, and controls; Westinghouse motors, generators, and controls; Allis-Chalmers motors and generators and Cutler-Hammer controls; Elliott motors and generators and Westinghouse controls.

Some of the differences that exist in electrical and structural design of equipment produced by these manufacturers are illustrated and described in this and the following chapters.

 
B. MAIN AND AUXILIARY GENERATORS
 
2B1. Description of main generators. The following terms describe the characteristics of main generators: two wire, direct current, separately excited, shunt wound, compensated multipolar, totally enclosed, and self ventilated. The armature shafts for generators used with General Motors engines are supported at each end on a bearing; those used with Fairbanks-Morse engines are so supported only at the commutator end. The bearings are force-lubricated   by the oil supply from the main engine lubricating system.

The maximum speed of a main generator varies with the type of main engine. Maximum speed with a General Motors engine as a prime mover is 750 rpm; with a Fairbanks-Morse engine, 720 rpm. Direct flexible coupling to the engine is accomplished through the flanged end of the generator armature shaft.

With the exception of the cooling units on

 
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Figure 2-1. GENERAL ARRANGEMENT OF MAIN PROPULSION EQUIPMENT, GEAR DRIVE AND DIRECT DRIVE.

Figure 2-2. Cross-section of G.E. main generator.
Figure 2-2. Cross-section of G.E. main generator.
 
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Figure 2-3. Cutaway of Westinghouse main generator.
Figure 2-3. Cutaway of Westinghouse main generator.
Figure 2-4. Cutaway of Elliott main generator cooling unit.
Figure 2-4. Cutaway of Elliott main generator cooling unit.
  Figure 2-5. Cutaway of Allis-Chalmers main generator cooling unit.
Figure 2-5. Cutaway of Allis-Chalmers main generator cooling unit.
 
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Allis-Chalmers machines, the construction of all main and auxiliary generators is similar. The Main generators are rated at approximately 2650 amperes at 415 volts and 1100 kilowatts.

Detailed ratings and characteristics of the various machines are found in the individual manufacturer's instruction books.

Figure 2-6. Commutator end view of G.E. main generator.
Figure 2-6. Commutator end view of G.E. main generator.

Figure 2-7. Coupling end view of G.E. main generator section cover removed.
Figure 2-7. Coupling end view of G.E. main generator section cover removed.

  External views of various types of submarine propulsion generators are shown in Figures 2-2 through 2-10.

Figure 2-8. Commutator end view of Elliott main generator.
Figure 2-8. Commutator end view of Elliott main generator.

Figure 2-9. Commutator end view of Elliott main generator With front end bell removed.
Figure 2-9. Commutator end view of Elliott main generator With front end bell removed.

 
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Figure 2-10. Coupling end view of Allis-Chalmers main generator.
Figure 2-10. Coupling end view of Allis-Chalmers main generator.

2B2. Armature. The armature shaft is a single piece of forged steel. Coupling flanges, thrust collars, and oil deflectors are part of the shaft.

A spider for supporting the armature laminations is shrunk and keyed to the shaft. The core of the armature consists of magnetic steel punchings assembled in a group and secured to the spider by means of a shrink fit and keys. After the punchings are in position, a flange is pressed into place and held by circular keys.

2B3. Armature windings. Armature windings consist of a number of single turn coils. These coils are placed in slots on the armature and held in place by slot wedges. The ends of the coils outside the slots are held by nonmagnetic steel banding wire. The windings are insulated from their supporting flanges by pieces of mica. An equalizer winding is provided in all submarine generators. It consists of connections between points of equal voltage in the armature circuit for balancing the current in the various armature circuits. It is usually located at the commutator end of the machine in a recess provided in the flanged portion of the spider. It is insulated from other parts by layers of mica.

2B4. Commutator. The commutator consists of copper segments insulated from each other by

  mica, and held in position by V-shaped clamping rings. Mica is also used to insulate the segments from the clamping rings. The clamping rings are supported by through bolts or clamping studs, which, when tightened, hold the segments securely in position. The adjustment of these through bolts should never be changed.

Figure 2-11, Coupling end view of G.E. main generator armature.
Figure 2-11, Coupling end view of G.E. main generator armature.

2B5. Brush rigging and brush holders. The brush rigging consists of a circular steel yoke to which the brush holder assemblies are attached. Some types of yokes have gear teeth cut around the outer periphery and meshed with a removable pinion for rotating the rigging. Other types have holes drilled around the outer periphery into which a lever can be inserted to accomplish the same purpose.

Each brush holder is attached to a bracket which is secured to, but insulated from, the steel brush yoke. The brush holders contain brushes arranged two in a holder on each bracket. On General Electric and Elliott generators, one of the brushes in each holder runs with a leading angle and the other with a trailing angle. On Westinghouse and Allis-Chalmers generators, both brushes have a leading angle.

The complete brush rigging assembly is attached to the generator field frame and locked in position by clamps or studs. Access to the brush rigging lock is obtained by removing

 
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inspection cover plates located on the side of the machine.

Figure 2-12. Commutator end of G.E. main generator, with cooler, end bell, and upper half of bearing housing removed.
Figure 2-12. Commutator end of G.E. main generator, with cooler, end bell, and upper half of bearing housing removed.

Figure 2-13. Main generator brush rigging.
Figure 2-13. Main generator brush rigging.

2B6. Main field poles and coils. Each main field pole consists of a number of steel laminations riveted together and bolted to the frame. Each lamination has slots punched near the pole face to provide for insertion of the

  compensating windings (see Section 1E12). Shims between the poles and the frame permit adjustment of the air gap.

The main field coils are wound around, but insulated from, the pole piece body. All coil leads for each half of the field are carried to terminal blocks located inside the machine. Any disabled coil may be cut out of the circuit at these terminal blocks.

Figure 2-14. Brush holder and bracket.
Figure 2-14. Brush holder and bracket.

Figure 2-15. Main generator field frame and windings.
Figure 2-15. Main generator field frame and windings.

 
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2B7. Commutating field poles and coils. The commutating field poles (see Section lEll) are made either of laminated or solid steel plate and are bolted to the frame. There are magnetic and nonmagnetic shims between the pole piece and the frame for adjusting the air gap and strength of the commutating fields. The coil consists of several turns of solid copper bus bar fastened to the pole piece by means of insulated steel studs.

2B8. Compensating winding. The compensating winding (see Section lE12) consists of copper bars inserted in slots in the main pole pieces. The winding elements are insulated from the pole by mica and joined by copper bars bolted in place.

  the commutator end are lined with soft metal to take the thrust load.

Escape of oil from the housing is prevented by deflector rings on the armature shaft and by oil seals in each inner half of the bearing housing.

An air chamber around the shaft at the inside end of the bearing housing is vented by pipes to the outside of the machine. This prevents the formation of a vacuum around the shaft and provides a drain for any possible oil leakage before it reaches the interior of the machine.

The bearing is drained through a pipe equipped with an oil flow sight. To prevent an excessive flow of oil from reaching the bearing,

Figure 2-16. Miscellaneous field parts, Allis-Chalmers.
Figure 2-16. Miscellaneous field parts, Allis-Chalmers.
2B9. Terminals. The armature terminals are brought out through a terminal board. These terminals are silver plated to obtain low contact resistance.

2B10. Bearing and bearing lubrication. The bearing consists of a split shell, lined with soft metal, usually babbitt. It is carried in a split housing which is in turn bolted to the frame of the machine. The two halves of the bearing shell are accurately aligned by two dowel pins, one on each side. The ends of the bearing shells at

  and also to allow the use of openings in the feed line of not less than 3/16-in. diameter, some of the oil is bypassed around the bearing. Pressure at the inlet to the bypass chamber should be 10 to 15 pounds per square inch.

In order to remove the upper half of the bearing housing, it is necessary on some machines to remove an adapter plate first, thus providing sufficient clearance for lifting the bearing housing over the bearing. Lifting jackscrews are provided, which, when turned, lift

 
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Figure 2-17. Lower half of main generator bearing installed.
Figure 2-17. Lower half of main generator bearing installed.
the shaft slightly and permit rotation of the lower half of the bearing to the top of the shaft for removal (see Section 7A12). Serious casualties have been caused by failure of repair personnel to lower the jack after replacing a bearing.

Figure 2-18. Main generator bearing, coupling end.
Figure 2-18. Main generator bearing, coupling end.

  Figure 2-19. Main generator bearing, commutator end.
Figure 2-19. Main generator bearing, commutator end.

2B11. Cooling systems. The cooling systems of all the various machines operate on the same principle. The hot air is cooled by forcing it through water-cooled cores, The Allis-Chalmers machines, however, do not employ the ductwork

 
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used on the other makes of machines (see Figure 2-5). The cooling unit on these generators fits the contour of the machine and is made in two sections, each half-section covering one fourth of the outer surface of the generator. Water tubes are set in grooves on the outer surface of the shell to absorb the heat from the circulating air.

The other makes of machines have the water tubes mounted in cores, similar to an automobile radiator. This assembly is located in the air ducts of the cooling system through which the air passes.

Circulation of air is effected by the ventilating fan attached to the armature shafts. Air is delivered from the cooler into the commutator end housing. It is then drawn through the field coils and through the commutator ends, under the commutator into the armature, and then through ventilating ducts in the armature core. On Westinghouse generators the fan is located on the commutator end and the air flow is thus reversed.

  Figure 2-20. Bottom view of G.E. main generator cooling unit.
Figure 2-20. Bottom view of G.E. main generator cooling unit.
Figure 2-21. Cutaway of Westinghouse auxiliary generator.
Figure 2-21. Cutaway of Westinghouse auxiliary generator.
 
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The coolers are designed to deliver air at 104 degrees F to the windings. The air entering the coolers may vary in temperature, depending on the type of machine. The manufacturer's instruction books give the maximum allowable temperatures of the air from the windings.

2B12. Description of the auxiliary generator. The 300-kw direct current auxiliary generator Is a two-wire, compensated, differential compound machine. The generator is self-excited, but the switching is arranged so that separate excitation may be obtained from the battery. The machines can produce 300 kw at 1200 rpm at any voltage from 260 volts to 345 volts, and 150 kw at 600 rpm at 260 volts.

The generator is connected to the auxiliary Diesel engine through a semirigid coupling. The commutator end of the armature shaft is supported on a sleeve bearing which is force-lubricated from the engine lubricating system. The opposite end of the shaft is carried by the engine bearing. The generator armature thrust is taken by thrust collars on the shaft and thrust faces on the ends of the sleeve bearing.

In construction, auxiliary generators differ only in minor detail from the main generators. They are produced by the same manufacturers and, with the exception of differences in size, weight, and number of some of the components,

Figure 2-22. Right front view of G.E. auxiliary generator.
Figure 2-22. Right front view of G.E. auxiliary generator.

  the auxiliary and main generators are identical.

The rating and classification of the auxiliary generators can be found in the manufacturer's instruction book furnished with the equipment. The various makes and some of the principal components are illustrated in Figures 2-21 through 2-30.

Figure 2-23. Front view of G.E. auxiliary generator, end shield and cooler cover removed.
Figure 2-23. Front view of G.E. auxiliary generator, end shield and cooler cover removed.

Figure 2-24. Commutator end view of Elliot auxiliary generator.
Figure 2-24. Commutator end view of Elliot auxiliary generator.

 
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Figure 2-25. Elliott auxiliary generator, end bell and cooler removed.
Figure 2-25. Elliott auxiliary generator, end bell and cooler removed.

Figure 2-26. Commutator end view of Allis-Chalmers auxiliary generator, end cover removed.
Figure 2-26. Commutator end view of Allis-Chalmers auxiliary generator, end cover removed.

  Figure 2-27. Later type Allis-Chalmers auxiliary generator.
Figure 2-27. Later type Allis-Chalmers auxiliary generator.

Figure 2-28. Armature for G.E. auxiliary generator.
Figure 2-28. Armature for G.E. auxiliary generator.

 
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Figure 2-29. Allis-Chalmers auxiliary generator brush rigging.
Figure 2-29. Allis-Chalmers auxiliary generator brush rigging.
 
Figure 2-30. Miscellaneous field parts, Allis-Chalmers auxiliary generator.
Figure 2-30. Miscellaneous field parts, Allis-Chalmers auxiliary generator.
 
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Figure 2-31. Cross section of G.E. main motor.
Figure 2-31. Cross section of G.E. main motor.
 
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C. MAIN MOTORS
 
2C1. Description of geared main motors. The geared type main motors are of the two-wire, d.c., compound type with shunt, series, commutating, and compensating field windings. Separate excitation for the shunt field is provided by the excitation bus which receives power from either battery.

The motors are totally enclosed, watertight below the field frame split and waterproof above. Cooling is accomplished by a fan which is attached to the armature shaft and circulates the air through cores cooled by circulating water.

Each end of the armature shaft is supported on a split sleeve bearing. The bearings are lubricated from the oil supply in the reduction gear units.

Various combinations of armatures in series or in parallel, including the coupling of all four motors in series for dead slow operation, may be obtained, for either surface or submerged operation, through the main control cubicle.

For surface operation, motor speed control is accomplished by controlling the generator speed and shunt field, thus varying the voltage supplied. When submerged, speed is controlled

Figure 2-32. Cutaway of Elliott main motor cooler section.
Figure 2-32. Cutaway of Elliott main motor cooler section.

  by varying the motor shunt field or by connecting the motors in different combinations of series and parallel. Reverse operation is accomplished by reversing the direction of the flow of current in the motor armature circuit.

Figure 2-33. Cutaway of Allis-Chalmers main motor cooler section.
Figure 2-33. Cutaway of Allis-Chalmers main motor cooler section.

Figure 2-34. Commutator end view of G.E. main motor.
Figure 2-34. Commutator end view of G.E. main motor.

 
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Figure 2-35. Coupling end view of G.E. main motor, flat cover plate and air duct cover removed.
Figure 2-35. Coupling end view of G.E. main motor, flat cover plate and air duct cover removed.
  Main motors used in a gear drive installation are classed as high-speed motors and each is rated for continuous duty at approximately 1370 hp, 415 volts, 2600 amperes, and 1300 rpm.

Figure 2-36. Commutator end view of Elliott main motor.
Figure 2-36. Commutator end view of Elliott main motor.

Figure 2-37. Elliott main motor with end bells removed.
Figure 2-37. Elliott main motor with end bells removed.
 
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2C2. Commutator, armature, armature windings, brush rigging, brush holders, field frame, and windings. Figures 2-38 through 2-42 illustrate these parts. They are practically identical in construction with the corresponding parts of a main generator. For their description, see Section 2B.

Figure 2-38. Coupling end view of G.E. main motor armature.
Figure 2-38. Coupling end view of G.E. main motor armature.

Figure 2-39. Main motor brush rigging.
Figure 2-39. Main motor brush rigging.

  Figure 2-40. Main motor field frame and windings.
Figure 2-40. Main motor field frame and windings.

Figure 2-41. Main coil on pole piece with compensating field bars.
Figure 2-41. Main coil on pole piece with compensating field bars.

Figure 2-42. Commutating field toil on pole piece with compensating field bars.
Figure 2-42. Commutating field toil on pole piece with compensating field bars.

2C3. Bearings. As in the main generators, the armature shaft of a main motor is supported on a split sleeve with a spherical or cylindrical seated bearing at each end. The two halves of the bearing are held together between two halves of the bearing housings which are clamped together and bolted to the bearing brackets. End clearance at the commutator end is large enough to make certain that the thrust

 
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load will be taken by the coupling end bearing only. Each bearing is sealed against oil leakage by deflector rings and oil seals. The bearing temperatures are measured by Brown resistance temperature units, the detectors of the units being located in the lower halves of the bearings. The maximum safe operating temperature of the bearings is 180 degrees F.

2C4. Lubrication. Oil under pressure is supplied to the motor bearings by a gear-driven lubricating oil pump which is attached to the reduction gear units of each pair of motors. However, when the propeller shaft speed is below 38 rpm, a standby pump which supplies sufficient oil pressure both for reduction gears and main motor bearings is placed in operation. Oil catching grooves and return drains in the housing prevent leakage of oil along the shaft into the windings. An air chamber between the bearing and the interior of the motor serves to prevent the formation of a vacuum around the shaft and permits drainage of any possible oil leakage before it reaches the interior of the motor. A safety overflow is provided in the housing oil reservoir to prevent possible flooding of the winding if the drain should become clogged. After passing through the bearing, the oil passes out of the housing through a sight flow and returns to the lubricating oil sump. When the flow of oil at the sight flow glass appears to be appreciably reduced or, if the oil pressure falls below 5 psi, the standby pump must be placed in operation. The standby system is also used to force lubricant to the bearings before starting the motors after a shutdown period.

2C5. Cooling systems. The main motor cooling units are similar to the main generator units with one exception. The Allis-Chalmers cooling units on the main motor are constructed in three sections and cover approximately 90 percent of the outer surface of the motor frame. The remaining surface is covered with a dummy section to secure the necessary clearance for the motor arrangement in the motor room. The arrangement is such that each motor has its cooler sections placed on different portions of its outer surface.

2C6. Description of double armature propulsion motor. a. General. On the latest classes of submarines, main motors and

  reduction gears have been replaced by two 2700-hp double armature motors, directly connected to the propeller shafts, one to the starboard, the other to the port shaft.

The motors are of the two-wire, d.c., compound, compensated type with shunt and series field windings and commutating poles. Separate excitation for shunt fields is provided by the excitation bus which receives power directly from the battery buses in the control cubicle. The motors are totally enclosed and a water tube air cooler is mounted crosswise over the motor frame. Mechanical air filters are located in the air ducts between the coolers and vent blower. A separate motor-driven fan circulates the cooling air. When the motors are operating in the SLOW position, neither cooling air nor circulating water is required. The motor for the ventilation fans normally is connected across the terminals of one of the propulsion motor armatures. When the bus selector lever is in the SLOW position, this connection is opened.

If at any time it becomes necessary to disconnect the propulsion motor armature to which the vent blower is normally connected, and still operate the other propulsion motor armature, the vent motor connections can be shifted to the armature intended for operation by means of connector links provided in the vent motor leads in the control cubicle.

The motor frame is split at an angle of approximately 11 degrees from the horizontal centerline to permit easy removal of the armature. The motor is watertight below this joint and waterproof above.

The armature is mounted on a hollow forged steel shaft which is flanged at the after end for coupling to the propeller shaft. Each end of the shaft has a bearing journal for a force-lubricated, split sleeve bearing mounted in a pedestal separate from the frame. In addition to the radial bearing, the forward end of the shaft is fitted with a collar for a Kingsbury thrust bearing which takes the propeller and motor thrust load.

To secure proper compensating field strength over the entire operating range, the compensating winding of each motor is shunted by a permanent resistor which is adjusted to give good commutation over the entire range.

 
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Figure 2-43. Cross section of Elliott double armature propulsion motor.
Figure 2-43. Cross section of Elliott double armature propulsion motor.
 
Figure 2-44. Cutaway of Westinghouse double armature propulsion motor.
Figure 2-44. Cutaway of Westinghouse double armature propulsion motor.
 
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Figure 2-45. Double armature propulsion motor.
Figure 2-45. Double armature propulsion motor.
b. Operation. For surface operation, using the various combinations of armatures and taking power from the main generators, the motors develop from 20 hp to 2700 hp per propeller shaft at speeds ranging from approximately 67 rpm to 282 rpm.

For submerged operation, using various combinations of armatures and taking power from the batteries, the motors develop power ranging from 30 hp to 1719 hp per propeller shaft and give a speed range from 38 rpm to 219 rpm.

c. Motor frame. The motor frame is constructed in two halves which are doweled together. Jackscrews in the supporting feet assist in shimming and properly aligning the frame. The frame and enclosures are watertight below the frame split and waterproof above. Any condensate or liquid from other sources that may find its way into the interior of the motor will

  drain into the bottom of the end enclosures or center section and may be drained off from there with a hand pump. Steel brackets are bolted and doweled to the frame sections for support of the brush rigging. Removable plates provide access to the connections.

d. Bearings. The radial bearing sleeves are carried in split cast steel pedestals. These are bolted to the motor bedplate which is welded to the hull. The caps of the bearing pedestals are held in position by fitted studs.

Bearing sleeves are made of cast steel lined with babbitt. They are machined to fit the spherical seat in the bearing pedestal and are secured against rotation by a dowel pin in the pedestal cap. The babbitt on the sides of the sleeves is cut away slightly to allow proper distribution of oil. Grooves through the sides of the sleeves at the horizontal split permit a circulation of oil in addition to that which passes under

 
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Figure 2-46. Double armature propulsion motor with enclosures removed.
Figure 2-46. Double armature propulsion motor with enclosures removed.

the shaft. This extra flow of oil passing over the shaft journal carries away heat and also tends to prevent collection of sludge in the bearings.

  A jacking beam is provided in the lower housing to support the shaft while removing bearing sleeves. The bearing pedestals and sleeves are drilled to permit the use of a depth gage for measuring bearing wear. A bridge gage may also be used for measuring bearing wear or to locate properly a new bearing shell.

The Kingsbury thrust bearing on the forward end of the shaft takes the thrust load of the propeller and motor in both ahead and astern directions. The bearing consists of a rotating collar keyed to the shaft, and stationary shoes with load-equalizing supports or leveling plates which allow for slight misalignment.

e. Lubrication. Oil is supplied to the bearings by a separate motor-driven lubricating oil pump for each shaft. Oil-catching grooves and felt wipers in the housing prevent leakage of oil along the shaft. After passing through the bearing, the oil passes out of the housing through a sight flow and returns to the sump tank.

A resistance type temperature detector for indicating bearing temperature is located in the lower half of each radial bearing and in the discharge oil from the Kingsbury thrust bearing.

f. Armature shaft. Except in Westinghouse motors, the armature shaft is a one-piece

Figure 2-47. Propulsion motor double armature, coupling end.
Figure 2-47. Propulsion motor double armature, coupling end.
 
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Figure 2-48. Propulsion motor double armature, thrust bearing end.
Figure 2-48. Propulsion motor double armature, thrust bearing end.
steel forging machined to proper fit for support of two armatures and their commutators. Westinghouse motors have two-piece shafts coupled together in the center. Three oil throwing collars are machined on the shaft one on each side of the bearing journal at the coupling end, and one on the forward end of the shaft.

g. Armature core, armature winding,

  commutators, brush rigging, brush holders, and field windings. With the exception of minor details, the construction of these components is similar to that of the corresponding parts of a high-speed main motor or generator. The field frame and windings are illustrated in Figure 2-49. For specific details refer to the manufacturer's instruction book furnished with the equipment.
Figure 2-49. Double armature propulsion motor field frame and windings.
Figure 2-49. Double armature propulsion motor field frame and windings.
 
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D. CABLES
 
2D1. General. Each of the various types of electrical cables used on submarines has a certain number of conductors and a type of insulation designed for a specific application. Each type and size has a definite rating with respect the maximum operating voltage for which it is designed, the maximum load in amperes to   Cables are identified as to type by letters followed by a number that indicates for power cables the size in circular mils. For interior communication and fire control cables, the number indicates the number of conductors or pairs of conductors. For example, the designation SHFL-800 identifies a single conductor,
Figure 2-50. Type SHFL single conductor heat and flame resistant leaded cable.
Figure 2-50. Type SHFL single conductor heat and flame resistant leaded cable.
 
Figure 2-51. Type DCP double conductor portable cable.
Figure 2-51. Type DCP double conductor portable cable.
be carried under specified conditions, the maximum extremes of temperature to which the cable would normally be exposed, and its relative resistance to moisture or flame. The construction of three types of cables is illustrated in Figures 2-50, 2-51, and 2-52. The labeled parts will be helpful in understanding the inner composition of the various cables illustrated.   heat and flame resistant, leaded cable with an area of approximately 800,000 circular mils. An MHFA-10 cable is a multiple conductor, heat and flame resistant, armored cable of 10 conductors.

To facilitate tracing of cable for purposes of maintenance and replacement, metal tags stamped with a circuit marking are attached

 
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Figure 2-52. Type MHFA multiple conductor beat and flame resistant armored cable.
Figure 2-52. Type MHFA multiple conductor beat and flame resistant armored cable.
to the cables (see "How to Read a Cable Tag," Section 20D). For specific information on the routing of a cable run, consult the wiring deck plan applying to the specific installation.

2D2. Main power cables. The following is a list of the types and numbers of cables and their approximate length as used on a few of the main power circuits. This description is of a typical installation. Considerable variation will be found in the various classes of submarines.

1. Forward battery to maneuvering room. This circuit employs 12 type SHFL-800 cables, each of which is approximately 150 ft long. In addition, there is 1 type DHFA-9 ammeter lead, 170 ft long.

2. Auxiliary power distribution switchboard; circuit run from forward battery to control room. This circuit employs 4 type SHFL-650 cables, each of which is 35 ft long, and 1 type SHFA-75 neutral lead of the same length.

3. After battery to maneuvering room. This circuit employs 8 type SHFL-800 cables, each of which is approximately 85 ft long, and 1 type DHFA-9 ammeter lead, approximately 110 ft long.

4. Main generators to maneuvering room. These circuits employ 8 type SHFL-1000 cables, 4 cables for the positive and 4 for the negative legs. The No. 1 and No. 2 generator cables run from the forward engine room to the maneuvering room; the No. 3 and No. 4 generator cables run from the after engine room to the maneuvering room. Each of the 8 No. 1 and No. 2

  generator cables are approximately 50 ft long. Each of the 8 No. 3 and No. 4 generator cables are approximately 15 ft long. Shunt field, ammeter, and voltmeter cables are type DHFA-4, DHFA-9, and DHFA-3 respectively.

5. Main motor armature and series field, positive and negative. The No. 3 and No. 4 main motor circuits employ 16 type SHFL-800 cables for each motor, 4 cables for each armature leg and 4 cables for each series field leg. Each cable is approximately 15 ft long. All main motor shunt field leads are of type DHFA-4 cable, approximately 20 ft long. No. 1 and No. 2 main motors are similarly connected but on some installations bus bars are used instead of cables. Each bar or cable is approximately 4 ft long.

6. Auxiliary generator cable run from aft engine room to maneuvering room. The positive and negative leads of this circuit employ 4 type SHFL-650 cables (2 cables per leg), each of which is approximately 55 ft long.

7. Bus tie to auxiliary power distribution switchboard. This circuit runs from the maneuvering room to the control room and employs 4 type SHFL-650 cables (2 cables per leg), each of which is approximately 150 ft long.

8. Shore connection. This circuit runs from the after torpedo room to the maneuvering room and employs 4 type SHFL-650 cables (2 cables per leg), each of which is approximately 45 ft long.

 
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