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Figure 4-1. DIAGRAM OF AUXILIARY POWER CIRCUITS.

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AUXILIARY POWER CIRCUITS
MOTORS, AND CONTROLS
 
A. GENERAL
 
4A1. Description. Approximately 50 auxiliary motors of various capacities are located throughout the ship for operation of compressors, blowers, pumps, and other miscellaneous equipment. Current for operation of these motors is supplied by the auxiliary generator, the main batteries, or a combination of both, through two auxiliary distribution switchboards. The forward distribution switchboard, connected to the forward battery, feeds all auxiliary machines in and forward of the control room, while the after distribution switchboard, powered by the after battery or the auxiliary generator, feeds all auxiliary machines aft of the control room. A   bus-tie circuit connects the two switchboards, making it possible to feed one switchboard from the other in an emergency.

During normal operation, the bus-tie circuit is left open and the power for both switchboards is taken from the batteries, with the auxiliary generator often floating on the line. The batteries are connected in parallel through the battery selector in the main control cubicle. With the circuit so connected, the auxiliary generator contributes current not used by the auxiliary load toward charging the batteries. This circuit arrangement is also used when the auxiliary generator is secured.

Figure 4-2. Forward auxiliary power switchboard.
Figure 4-2. Forward auxiliary power switchboard.
 
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Figure 4-3. After auxiliary power switchboard.
Figure 4-3. After auxiliary power switchboard.
4A2. Shore connection. The bus-tie circuit is equipped with terminals to which an outside source of power, such as a shore connection or tender, can be connected for operation of the auxiliary circuits. The procedure to be followed in connecting the shore cables for operation of the auxiliary circuits is as follows:

1. Make certain that both bus-tie switches are open.

2. Check the polarity of the 250-volt external power supply.

3. Connect the positive lead to the positive terminal of the shore connection block and the negative lead to the negative terminal of the shore connection and energize the circuit.

4. Trip the auxiliary board battery breakers and close the bus-tie switches on both auxiliary power switchboards.

5. Current is now available from the

  external source through both auxiliary power switchboards.

To connect shore cables for charging the batteries, proceed as follows:

1. Place the battery selector lever in the main control cubicle in the OFF position.

2. Check the polarity of the external power supply.

3. Bring the shore cables down through the after engine room hatch.

4. Connect the positive lead to the positive terminal and the negative lead to the negative terminal on the battery bus in the control cubicle.

5. To charge both batteries, move the battery selector lever to the BOTH BAT. position.

6. To charge a battery separately, place the battery selector lever on FORWARD BATTERY or AFTER BATTERY position.

 
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B. AUXILIARY MOTORS
 
4B1. Description. Auxiliary motors are direct current motors designed to operate on a voltage ranging from 175 volts to 345 volts. Their horsepower rating, type of winding, and other data are given on the name plate attached to each motor. Auxiliary motor frames are enclosed to provide protection against dripping water and are vented to permit the escape of Figure 4-4. D.C. motor for antenna and periscope hoist, equipped with magnetic disk brake.
Figure 4-4. D.C. motor for antenna and periscope hoist, equipped with magnetic disk brake.

Figure 4-5. D.C. motor for air-conditioning compressor.
Figure 4-5. D.C. motor for air-conditioning compressor.

  Figure 4-6. D.C. motor for high-pressure air compressor.
Figure 4-6. D.C. motor for high-pressure air compressor.

Figure 4-7. D.C. motor for hull ventilation supply fan.
Figure 4-7. D.C. motor for hull ventilation supply fan.

 
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Figure 4-8. D.C. motor for battery ventilation fan.
Figure 4-8. D.C. motor for battery ventilation fan.

hot air which is forced out by a fan attached to the armature shaft. Magnetic disk brakes are used on motors which must stop after the current is shut off (see Section 4E1). A few of

  the various types of auxiliary motors are shown in Figures 4-4 through 4-10. Their electrical and mechanical details are similar to those of the main generators and motors. Figure 4-9. D.C. motor for drain pump.
Figure 4-9. D.C. motor for drain pump.
Figure 4-10. D.C. motor for trim pump.
Figure 4-10. D.C. motor for trim pump.
 
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C. MOTOR GENERATOR SETS
 
4C1. Description. There are two types of motor generator sets, lighting motor generator sets and I.C. ( interior communication) motor generator sets.

a. Lighting motor generator sets. These machines are used on some ships to deliver current for the operation of the lighting system as well as for the I.C. motor generator sets which require a lower voltage than that delivered directly by the battery or auxiliary generator. The 175- to 345-volt d.c. motor receives its power from the battery or auxiliary generator and through a common shaft drives the 120-volt generator. It is controlled by a speed regulator

  similar to that described in Section 9A1 for the I.C. motor generator sets.

NOTE. On some ships lighting motor generator sets have been superseded by lighting feeder voltage regulators (see Section 6D1).

b. I.C. motor generator sets. I.C. motor generator sets are d.c.-a.c. machines equipped with speed and voltage regulators to produce a 60-cycle current for interior communication, radio, radar, and sonar systems. The d.c. motor receives its power from the lighting motor generator on some ships, or directly from the battery or auxiliary generator on others.

Figure 4-11. Motor generator set.
Figure 4-11. Motor generator set.
 
D. CONTROL EQUIPMENT
 
4D1. Magnetic contactor starting panels. Most of the auxiliary motors are controlled through a magnetic contactor starting panel with push-button control for starting and stopping the motor.

The push-button station may be located some distance away from the motor in which case an indicating light in the push-button case will signify that the motor is running. This light is connected across the motor armature, or through an auxiliary contactor in the starting panel and will burn at maximum brightness only after the last step of starting resistance has been cut out of the motor circuit.

  When the ON button is pressed, the coil of the main contactor is energized, causing the contactor to close and thus connect the motor to the line through two or three steps of resistance. The number of steps of resistance used depends upon the size, capacity, and duty load of the motor.

Acceleration is controlled by the action of adjustable series relays. When the inrush current decreases to the value for which the relays are adjusted, the contacts of the first series relay close and energize the coil of the first accelerating contactor. This contactor closes and shorts out the first resistor step. When the second

 
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Figure 4-12. Magnetic contactor starting panel.
Figure 4-12. Magnetic contactor starting panel.
 
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in-rush of current decreases to the amperage for which the relays are adjusted, the contacts of the last series relay close. The last accelerating contactor then closes and shorts out the second resistor step and places the motor across the line.

NOTE. On controllers of Westinghouse manufacture, acceleration is controlled by fixed time delay relays instead of current relays.

The operation of the controller is subject at all times to the operation of an overload relay which opens the circuit to the main contactor on excessive overloads.

Some overload relays are provided with a time delay mechanism which allows a momentary overload. The time lag is produced by an oil dashpot. When the current taken by the motor rises to approximately 175 per cent of full load current, a plunger is drawn forcibly upward against the action of the dashpot,

  reaching its upward limit and opening the contacts in approximately 1 1/2 to 2 seconds.

Thermal overload relays used in some controllers consist of a heater coil, solder tube, control contacts, ratchet mechanism, and compression spring. Under normal conditions, the contacts of the relay are closed. The spring is then under compression and tends to open the contacts, but is prevented from opening them, however, by the outer part of the solder tube holding the ratchet mechanism. When the current to the heater coil becomes great enough to melt the solder holding the outer part of the tube, this part of the tube rotates and releases the ratchet mechanism to open the control contacts. The opening of these contacts breaks the circuit to the coil of the contactor handling the power circuit and this circuit is opened. As soon as the power circuit is opened, the solder film cools and hardens, and the relay is ready to be reset by means of the reset button.

Figure 4-13. Simplified schematic diagram of automatic motor starter.
Figure 4-13. Simplified schematic diagram of automatic motor starter.
 
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Figure 4-14. Magnetic disk brake.
Figure 4-14. Magnetic disk brake.
 
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E. MAGNETIC BRAKES
 
4E1. Description and operation. Magnetic disk brakes are used on the following auxiliary motors for stopping the rotation of the armature after the current has been shut off: periscope and vertical antenna hoist, bow plane tilting, stern plane tilting, after capstan, anchor windlass, bow capstan, bow plane rigging, and steering gear.

The hub of the brake is keyed on each side and is attached to the hub so that there is no relative rotation, but so that the disk may move axially on the hub. The exposed friction lined face engages with the stationary friction face on the mounting plate through pressure of a spring. The amount of pressure and the resulting torque can be adjusted by changing the spring compression. The field, armature, and coil constitute an electromagnet which overcomes the spring force and moves the armature

  and the adjustable friction plate toward the field when the coil is energized. This provides clearance between the friction faces and allows the motor shaft to turn freely. When the coil is not energized, the brake can be released by hand by pulling a lever plate axially away from the brake magnet. When the lever is released, the brake resets itself.

4E2. Magnetic gap adjustment. With the magnet deenergized, measure the amount the sounding pin can be pushed in. Make a similar measurement with the magnet energized. The difference between the two measurements is the magnetic gap. As the linings wear, the magnetic gap increases. When the gap approaches the maximum allowable limit as specified by the manufacturer, it must be readjusted. Refer to the manufacturer's instruction book for specific data and adjustment procedures.

 
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