6A1. General. A circuit breaker is a device for opening an electrical circuit under load and it can also be used as a switch for closing the circuit. Circuit breakers may be either automatic or nonautomatic in operation. They are of two general types for direct current applications: carbon tipped and quenched arc types. The Navy designations for these types are ACB (automatic carbon break), and AQB (automatic quenched break) or NQB (nonautomatic quenched break).

The type ACB is represented on submarines by the I.T.E. type KN used on Electric Boat Company vessels and the General Electric type AL-2N used on Portsmouth vessels. The AQB types are represented by Westinghouse breakers and are used only on vessels of Portsmouth design previous to SS 381. On later Portsmouth vessels and on all Electric Boat Company vessels they are replaced with fused switches.

6A2. Type ACB breakers. The ACB breakers (Figure 6-1) used on submarines are live front, two pole, manually operated and trip free. They are enclosed for protection of personnel and are fitted with overload and short circuit protection and, in the case of the auxiliary generator breaker, with reverse current protection. They are equipped with a manual tripping handle which may be used as a hold-in device and, on the older less shockproof models, can be turned to lock the breaker in. Since this renders the breaker unable to open under overload, it should never be left in the locked position after the immediate danger of opening due to shock has passed. The overload protective device acts to trip the breaker after a time delay when the current exceeds a certain value, usually 125 percent full load. The time delay is obtained by an oil dashpot which consists of two accurately ground disks in a bath of oil. When the disks are close together, the oil film between them resists the efforts of the tripping solenoid to pull them apart. The time delay is inversely

  proportional to the current and thus, on a large current, the device trips faster. With currents greater than about 800 percent of rated current the solenoid pulls so hard that the whole dashpot is lifted against a strong spring. This trips the breaker in a short time and is known as instantaneous short circuit protection.

Reverse current protection is provided on the auxiliary generator breaker to prevent damage to the engine should the generator attempt to act as a motor when connected across the battery. This device consists of a small torque motor, that is, a motor that attempts to rotate but cannot turn a whole revolution. The field poles of the motor are energized by the line current in one pole of the breaker and the armature is energized by a coil connected across the two poles.

When the current is flowing in the normal direction the motor tends to rotate in one direction but is prevented from so doing by a stop. Should the current in the breaker reverse, the motor tends to rotate in the other direction. When the current reaches a certain value, the torque overcomes the pull of a calibrating spring and rotates until it hits a plunger which trips the breaker. The calibration range of the reverse current trip is usually from 10 percent to 25 percent of the rated current. The action of the ACB breaker in rupturing the arc is simply a drawing out of the arc between the carbon tips as they separate. The linkage is designed so that the last points to separate are on the carbon tips, thus preventing burning of the current-carrying contacts which are silver tipped for low contact resistance.

6A3. Type AQB and NQB breakers. Type AQB and NQB circuit breakers used on submarines are dead front, two pole, manually operated, and on AQB breakers are trip free and fitted with short circuit protection. The arc in this breaker is interrupted in the following manner: As the contacts separate, the arc is drawn into a steel box insulated from the rest of the


Figure 6-1. Type ACB circuit breaker.
Figure 6-1. Type ACB circuit breaker.
  breaker and slotted so that the are is separated into several pieces, thus greatly lengthening it and cooling it. Magnetic forces set up between the arc and the steel box cause the arc to move into the box.

The short circuit feature provided on AQB breakers consists of a short circuit trip element that is usually calibrated at the factory and is not easy to adjust. The best practice is to replace the element with a new one having the desired tripping characteristics. When tripped, the handle of the AQB breaker returns to a position between OFF and ON. In order to reset it, the handle must be pushed toward OFF first and then to ON. NQB circuit breakers are entirely manual in operation and open only when the handle is turned to OFF. They have the same arc-interrupting features as the AQB breakers.

All AQB breakers are provided with a manual means of holding them in against overload and they can be locked closed against overload or shock. The locking devices should never be engaged except when absolutely necessary to prevent opening due to shock.

Figure 6-2. Type AQB circuit breaker, cover removed.
Figure 6-2. Type AQB circuit breaker, cover removed.



6B1. Fuses. Like circuit breakers, fuses are used to provide protection from short circuits. However, once the fuses have opened the circuit because of a short circuit, they cannot be closed and must be replaced. Fuses depend for their action on the melting of a current-carrying strip of metal by the heat generated by the current in the strip itself. Fuses are generally selected so that they will interrupt the circuit when about 200 percent of the rated current passes through them. All fuses have a time delay action which is inversely proportional to the current. This is caused by the heat capacity of the fuse and surrounding parts. Care should be taken when installing fuses to see that good contact is made in the clips as a high-resistance connection will, generate heat and cause the fuse to blow at a low current.

6B2. Fused switches. Fused switches are used for disconnecting and connecting various loads on the auxiliary power system and to provide short circuit protection to the cables and

  distribution panels. The type used on submarines consists of metal boxes having fuses with knife blade connectors attached to a sliding piece inside the cover. When the cover is closed normally, the fuse and attached blades may make a connection across the split type posts in the box; but pressing to one side before closing the cover causes the blades to make no contact and they are thus locked in the electrically open position. Fuses should never be replaced with fuses of greater capacity than that shown on the circuit diagram or marked on the label plate at the fuse holder or on the switch box.

Fuse retainers are installed on all fuses that can be jarred out of their holders by shock. These may be insulating blocks held over a line of fuses by thumbscrews or attached to the inside of the cover of the box; or they may be small clips of spring steel which increase the tension of the fuse holder prongs. Fuse retainers should always be replaced if they are removed for any purpose.

6C1. Description. The lighting system includes the ship's service lighting system and the port and starboard emergency lighting systems. Each of the systems is a separate distribution system.

Power for the ship's service lighting system on late type submarines is obtained from the batteries through 2 lighting feeder voltage regulators (see Section 6D1) and a lighting distribution switchboard. On earlier ships, power for this system was supplied by lighting motor generator sets (see Section 4C1).

On ships that take the lighting power directly from the batteries, a battery selector switch has been incorporated in the lighting distribution switchboard. This switch permits selection of either the battery or the shore connection as the source of power.

The feeders from the lighting distribution switchboard run the length of the ship on both sides and serve all regular lighting circuits through fused feeder distribution boxes. Final

  distribution to lighting fixtures and low-current outlets is through standard lighting distribution boxes with switches and fuses for each outgoing circuit.

The starboard emergency lighting system is powered directly through 2 cutout switches connected to the positive and negative end cell terminal connectors of the forward battery. These switches are connected to 13 lighting units, a circuit to the auxiliary gyro, and to the forward and after marker buoy circuits. A branch junction box provides a connection to the gyrocompass control panel for the alarm system.

The port emergency lighting system is directly powered through cutout switches connected to the positive and negative end cell terminal connectors of the after battery. The arrangement of this system is similar to that of the starboard emergency system except for the location of the circuits and the fact that there is no gyrocompass alarm connection.


Each lighting unit consists of two 115-volt lights, a protective resistor, and a snap switch, all connected in series as they always operate directly on full battery voltage.

6C2. Searchlight. The 12-inch incandescent signal searchlight requires a 120-volt d.c. supply. It is not considered a part of the lighting system because the supply is taken from a fused, double pole, single throw switch on the I.C. switchboard and led to a pressure-proof receptacle and snap switch on the bridge.

6C3. Maintenance.Pressure-proof type searchlights that are left in place permanently

  must be kept thoroughly clean and lubricated. The pressure-proof feature consists of a free flooding structure that drains rapidly after the submarine surfaces. Power should not be applied to the lamp until it has been out of the water approximately 2 minutes. Special care must be taken to keep all electrical connections clean, the moving parts lubricated and the aluminum surfaces painted to prevent corrosion.

CAUTION. Submerging with the light on or shortly after it has been used will break the searchlight bulb due to thermal shock. Diving with the light on or turning it on while submerged will blow the fuses.

6D1. Description. Lighting feeder voltage regulators are used on some ships instead of motor generator sets, for the purpose of maintaining the lighting system voltage at 120 volts or below. Two units are used, one for the starboard and one for the port lighting circuits.

These regulators are basically rheostats in which a contact arm is moved, either manually or by a motor, across a circular rheostat contact face plate. Resistor tubes dissipate the excess voltage in the form of heat. When the battery voltage is high as, for example, during charging, the supply to each of the lighting voltage regulators which is obtained from one half of the batteries may be as high as 175 volts. The rheostat is then adjusted to absorb the difference between this supply voltage and the desired 120-volt load-voltage. The rheostat resistance is tapped so that it produces a voltage drop of not more than 2 1/2 volts per step at any current between 100 amperes and 12.5 amperes. The rheostat is designed to dissipate 5500 watts at the maximum condition of a 55-volt drop at 100 amperes. This rheostat will carry between 12.5 amperes and 100 amperes through a drop of 0 to 55 volts.

The assembly is actuated through a voltage regulator element, known as an HIR regulator element, and RAISE and LOWER relays. The element is a voltage-measuring device that balances the pull of its coils against the pull of a coil spring. The RAISE and LOWER relays serve to connect the rheostat motor so that it

  rotates in one direction or the other in response to the voltage sensitive element.

Essentially, the regulator element has 2 parts, one moving and the other stationary. The moving armature carries a moving arm and is supported by 2 flat hinge springs. The stationary part consists of 2 stationary contacts with support members and magnetic circuit parts. One coil is mounted on each core. Each of these coils is rated at 27.5 milliamperes and has a resistance of 1950 ohms.

The coil spring is fastened between the moving arm and the stationary member by a lever which can be adjusted to obtain proper spring tension. The lower end of the moving arm carries 2 counterweights which statically balance the moving arm in a vertical position. The upper end of the moving arm carries a double face, moving contact between a pair of stationary contacts of the relays. These stationary contacts are the R (raise) and L (lower) contacts and can be adjusted to fix the operating position and travel of the moving armature in relation to the pole pieces.

The RAISE and LOWER relays consist of two parts, one stationary, the other moving. The stationary part consists of a base, core, coil, the stationary main contact, blowout coil, and the arc chute. The moving part carries the main moving contact at its upper end and a counterweight at its lower end for static balance.


The complete assembly is drip-proof in construction and louvers are provided for the escape of hot air. The maximum permissible temperature rise on the rheostat resistor tubes is 375 degree C.

CAUTION. Although the temperature may not reach the maximum of 375 degree C, care must be taken in handling or working around the equipment.

6D2. Manual operation. The correct procedure for manual operation of the regulators is as follows: Turn the control switch to the MANUAL position. Pull the rheostat handwheel to disengage the rheostat from the motor speed reduction gears. The voltage of the load is dependent upon the position of the rheostat arm. Turning the rheostat handwheel in a clockwise direction cuts out, or decreases, rheostat resistance and raises the load voltage. Turning the rheostat handwheel in a counterclockwise

  direction cuts in, or increases, rheostat resistance and lowers the load voltage.

6D3. Automatic operation. The following precaution must be observed before turning the control switch to the automatic (AUTO) position. Always adjust the rheostat position manually to give 120 volts on the lamp load. This is the value of voltage that the regulator element has been adjusted to maintain.

After manual adjustment to 120 volts, turn the control switch to the AUTO position. The moving contact of the regulator element will be centered or floating between the front and back stationary contacts. Both the RAISE and LOWER contacts will be open.

When the load voltage rises, either by load change or by increase of the charging generator voltage, the element closes its lower contact. This energizes the DECREASE relay, which

Figure 6.5. Schematic diagram of lighting feeder voltage regulator.
Figure 6.5. Schematic diagram of lighting feeder voltage regulator.

Figure 6-6. Lighting feeder voltage regulators and lighting distribution switchboard.
Figure 6-6. Lighting feeder voltage regulators and lighting distribution switchboard.

closes its contact in the motor field circuit. The motor drives the rheostat arm in a counterclockwise direction to cut in resistance and lower the load voltage. The action is continuous until the voltage is restored to 120 volts.

When the load voltage is lowered, the element closes its contact. Provided the load voltage has not been lowered to a value less than 50 volts, the increase relay closes its contact in the motor field circuit. The motor drives the rheostat arm in a clockwise direction to cut out resistance and raise the load voltage. The action is continuous until the voltage is restored to 120 volts.

NOTE. Large increases in load (over 50 amperes) should not be thrown on when the control switch is set on AUTO as this may cause the load and control voltage to fall below 50 volts, in which case the INCREASE and DECREASE relays and rheostat driving motor will

  Figure 6-7. Lighting feeder voltage regulator, top removed.
Figure 6-7. Lighting feeder voltage regulator, top removed.

Figure 6-8. Top view of lighting feeder voltage regulator.
Figure 6-8. Top view of lighting feeder voltage regulator.


fail to operate. In general, when set for automatic control, load steps should not exceed 50 amperes. Under manual control, precautions as to amount of load increase are not necessary, because the operator can take care of any load change within the rating of the rheostat. In view of the fact that overvoltage greatly reduces incandescent lamp life, when using manual control, an operating procedure should be established that will prevent large amounts of overvoltage.

6D4. General maintenance.The equipment requires only reasonable care to keep the contacts and the control element free of dust or dirt. The element contacts may be cleaned and polished without removing the contacts. A clean

  dry cloth should be used; emery cloth or other abrasives should never be used.

Moving parts should be checked periodically for free operation and to see that all moving contacts are in proper alignment with their stationary contacts. Main and auxiliary contacts should close at approximately the same time. The air gap between the moving and stationary main contact should be approximately 1/8-inch. A screw on the bottom of the moving arm is provided for adjustment of the air gap.

Lubrication of the rheostat motor should be checked periodically. The motor is equipped with 2 oil filler pipes, each of which has a screw head plug to permit refilling.

6E1. Lubricating oil heaters. Four heater immersion units, each rated at 220 volts and 500 watts, are installed in each of the 2 lube oil heater assemblies. Each heater immersion unit consists of 3 blades separately enclosed in a steel sheath. The ends of the sheaths are brazed to the terminal housing of the immersion unit which is threaded for insertion into the heater housing pipe assembly.

In operation, the oil circulates through the heater housing pipes and, in its course, passes over each of the heater immersion units. The temperature necessary to bring the oil to its proper viscosity is controlled by cutting in or cutting out the required number of heaters, each of which is provided with an ON-OFF switch.

CAUTION. The immersion units must not be turned on unless oil is flowing. The units will burn out quickly if current is applied while they are not submerged in oil.

6E2. Air heaters. Portable 2-kw and 4-kw blower type heaters are installed on each vessel. The heaters are equipped with a switch providing 2 heating points. The switch positions are marked OFF, LOW, and HIGH. A self-contained fan is provided and is connected when the switch is turned to one of the heat positions. The 4-kw heater is rated 250 volts, at 16 amperes, and has 4 insulated heater sections cast in a circular fin type grid. Each pair of sections is protected by a thermal cutout, actuated by

  excessive sustained temperature and provided with an indicator showing that the cutout has tripped. The reset can be operated only after the machine has cooled to a safe operating temperature.

The 2-kw heater is rated 250 volts, at 8 amperes, and is similar in construction to the 4-kw heater except that each heater section is rated 500 watts, instead of 1000 watts.

Air heaters are fitted with protective devices to allow operation at 345 volts. However, during a long battery change at high voltage they may be turned to OFF or LOW as a further safety precaution.

6E3. Hot water heaters. The hot water tanks are of 20-gallon and 25-gallon capacity, heated by rod type heating units that are thermostatically controlled by magnetic contactors. The 20-gallon tank is equipped with 2 heating units, and the 25-gallon tank, with 3 heating units. Each heating unit is rated at 4 kw at 275 volts, and will operate satisfactorily over a range of 200 to 345 volts. Two watertight terminal boxes are provided. The lower box affords access to and contains the connections of the heating units. The upper box affords access to and contains the thermostat. The thermostat is adjustable for any temperature range from 120 degrees F to 180 degrees F and operates on a change of +- 5 degree F.

When properly vented, the tank is


completely filled with water at all times. The water temperature is maintained in accordance with the setting of the thermostat that controls the coil circuits of magnetic line contactors in the controller. When the water temperature falls below the thermostat setting, the thermostat closes the coil circuit, causing the contactors to close and connect the heating units to the line. When the water in the tank reaches the desired temperature, the thermostat opens, opening the contactors and disconnecting the heating units from the line. Operation of each tank is controlled by an ON and OFF tumbler switch located on the magnetic line contactor panel.

6E4. Coffee urns. The urn consists of 2 cylinder-type containers, one mounted within the other. An air chamber between the containers prevents cooling of the coffee in the inner container when fresh water is run into the water tank.

The water tank is heated by 2 immersion units, both controlled by a single 3-heat-indicating, reversible control switch mounted in a switch box located in front of the unit. The immersion heating units are installed through the back of the urn body in the lower part of the water compartment. The unit heads, terminals, and leads are housed under a removable cover plate.

Each of the heating units has a rating of 1000 watts at 250 volts. The input of the urn, at rated voltage, is 2000 watts on HIGH, 1000 watts on MEDIUM and 500 watts on LOW. The urn capacity is 2 gallons of coffee and 4 gallons of water.

CAUTION. The heating units must not be turned on unless the urn is filled with water and must always be shut off or turned to LOW during a long battery charge at high voltage, in order to protect the units from the damaging high voltage.

  6E5. Galley range. The galley range consists essentially of a cooking surface and an oven. These units and their heating elements are supported in the reinforced range body. The cooking surface and the oven are each independently controlled by two 3-heat reversible indicating switches and each switch is protected by a double pole cutout.

The cooking surface heating elements consist of a nickel chromium resistor imbedded in an insulating material within a seamless steel sheath which is cast as a unit into the cooking surface casting. The cooking surface has an area of 19 inches by 18 inches and is rated at approximately 4000 watts on HIGH, 2000 watts on MEDIUM, and 1000 watts on LOW. The terminals are sealed to prevent air, moisture, or grease from entering the heating coils.

The insulated oven compartment is approximately 17 inches wide, 18 inches deep, and 14 inches high. The oven is provided with an adjustable automatic temperature control and indicator with a range between 200 degrees and 550 degrees F. Two heating elements are used; one is located at the bottom, the other at the top of the oven.

The oven heating elements are of the same construction as the cooking surface elements except that they are enclosed in nickel chromium tubing and are supported in a steel frame. Each heating unit is rated at approximately 1500 watts on HIGH, 750 watts on MEDIUM, and 375 watts on LOW at 250 volts.

All heating elements are capable of operating continuously at any voltage up to 345 volts without detrimental oxidation.

The range is constructed for heavy duty service and should require little electrical maintenance. Spare heating elements, switches and temperature control units are carried on board for replacements


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