GP9-5-758                                                ELECTRICAL EQUIPMENT

SECTION 5

ELECTRICAL EQUIPMENT

500 Basic Electrical Systems In full throttle, the rated horsepower of the engine is delivered to the direct coupled main generator. At the main generator the power of the engine is transformed into electrical power. The electrical power is then conducted to the four traction motors, two motors being located in each truck (each motor being geared to an axle).

The locomotive is designed so that within the current and voltage limits of the main generator, the power (KW) delivered to the traction motors at full throttle, is the same, regardless of the locomotive's speed.

The electrical system of the locomotive can be thought of as being divided into three separate systems:

• 1. High voltage system
• 2. Low voltage system
• 3. Alternating current system

The high voltage system is directly concerned with moving the locomotive; or in retarding the locomotive ~ten dynamic braking is used. The main components of the high voltage system are the main generator, traction motors, transition relays, shunt field contactor, motor shunting contactors, reversing contactors, wheel slip relays, ground relay, series and parallel power contactors. On locomotives equipped with dynamic brakes, the braking contactors, brake grids and brake grid blower motors may also be considered as part of the high voltage system.

The low voltage system contains the control circuits which control the flow of power in the high voltage system, and those auxiliary circuits conducting power to the locomotive lights, heater fans, fuel pump and the main generator battery field. A 64 volt battery, in the low voltage system, is the source from which power is taken to start the Diesel engine. Once the engine is started, the auxiliary generator takes over the job of supplying power to the low voltage system. The alternating current system includes an alternating current generator (called an alternator), four engine cooling fan motors, and four traction motor blower motors. The alternating current system provides a means of driving accessories, without the use of belt drives, at speeds which vary according to the speed of the engine.

501 Main Generator The main generator is a specially designed constant kilowatt (power) generator. A given amount of electrical power will be produced from the input of a given amount of mechanical power. Since power in watts is the product of volts times amperes it is seen that with a constant kilowatt generator, if the volts increase the amperage decreases, and vice versa.

Main generator voltage is nominally 600 volts but this varies with operating conditions. The output voltage of the main generator is controlled by the extent to which the main generator is automatically excited and the speed of the engine.

The main generator contains six field windings: starting, battery, shunt, differential, compensating and commutating. The starting field is used only when the main generator Is used as a starting motor to rotate the engine. With regard to locomotive operation, the shunt and battery fields provide the major excitation of the main generator.

The battery field provides the initial excitation of the main generator and is a low voltage, externally excited field. The current flowing through the battery field is varied by the action of the load regulator. By varying the strength of the battery field, the power output of the main generator is largely controlled.

The main generator is sell-excited by the shunt field. The shunt field is a high voltage field whose excitation varies with the voltage of the main generator. A shunt field contactor opens or closes the circuit to the shunt field.

The differential, compensating and commutating fields are permanently connected and are a matter of engineering design providing desired generator characteristics and proper commutation.

502 Traction Motors The traction motors are direct current, series wound motors geared to the driving axles. The motors are reversed by changing the direction of current flow in the field windings, the direction of current flow in the armature always being the same. This is accomplished by four reversing contactors, two of which (RVF1 and RVF2) are energized for forward operation and two others (RVR3 and RVR4) for reverse.

The traction motors are cooled by alternating current driven blowers, one for each motor. The traction motor blowers are mounted on the floor of the engineroom and blow air through flexible ducts to the traction motors. The speed of the blowers varies with the speed of the engine; this is due to the engine speed varying the frequency of the alternator.

The maximum permissible top speed of the locomotive is limited by the safe RPM of the traction motor armature; thus a high speed gear ratio is required for high speed train operation. A low speed gear ratio is needed to start and use full horsepower with low speed tonnage trains without overheating and damaging the electrical equipment.

Electro-Magnetic Reversing Contactor -- Fig. 5-1

503 Reversing Locomotive When the reverse lever in the cab controller is moved to either the forward or reverse positions, it establishes electrical circuits to energize the appropriate reversing contactors, Fig. 5 - 1. Contactors designated RVF1 and RVF2 would be energized for "Forward" operation while RVF3 and RVF4 are energizedfor "Reverse" movement of the locomotive. 504 Transition This term is applied to the changing of traction motor electrical connections on all Diesel-electric locomotives so that full power may be obtained from the main generator within the range of its current and voltage limits. To look at it another way, transition is a method of adjusting the traction motor "back pressure" (counter-e.m.f.) bucking the input of power from the main generator so that this back pressure will not become too high at higher speeds nor too low at lower speeds.

Standing still the traction motors have practically no "back pressure," or resistance to the input of current from the main generator. However, as the locomotive speed increases after starting in series-parallel (transition 1), Fig. 5-2A, the "back pressure" of the traction motors builds up and causes the main generator pressure (voltage) to increase so that it can continue forcing current into the motors. Although the main generator can vary its voltage over a wide range, there is a practical operating limit to its ability to increase its voltage. If this practical voltage limit were exceeded, the power output of the main generator, and correspondingly the engine, would drop off. To prevent this loss of power, a change is made in the electrical circuit just before the drop off begins.

The first change, Fig. 5-2B, from transition 1 to 2 (series-parallel shunt) connects a by-pass (shunt) circuit around each of the traction motor fields. Shunting the traction motor fields effects a reduction in the "back pressure" of the traction motors, which in turn allows the voltage in the main generator to reduce itself (with a constant KW generator, as the voltage goes down the amperage goes up, and vice versa). Thus, by shifting to transition 2 more current can pass through the traction motor armatures to maintain the full power output of the locomotive.

Series- Parallel Shunt Fig. 5-2B	Series- Parallel Fig. 5-2A
Parallel Shunt - Fig. 5-3B	Parallel - Fig. 5-3A

As the locomotive speed increases there is again a tendency for the power to drop off. This time, as the proper main generator voltage to current ratio is reached, a complete change in the electrical circuit is necessary to once again reduce the "back pressure" of the traction motors. When this change from transition 2 to 3 (parallel), Fig. 5-3A, is completed, the main generator continues the full application of power until a still higher locomotive speed is reached where power begins to drop off. At this time, the motor shunting contactors are again closed (Once again reducing the traction motor "back pressure") effecting transition from 3 to 4 (parallel shunt), Fig. 5-3B. With decreasing speeds, as caused by grades, a reverse sequence of transition takes place to prevent exceeding the current limitations of the main generator.

Two relays (FSR and FTP) actuate the changing of traction motor connections in the forward and backward transition.

E-I ty‡e transition is an automatic transition which, as the name implies depends primarily upon generator voltage and current (voltage and current ratio) for operation. Forward and backward transition are initiated by two (2) through cable type relays (FSR and PTR) which operate on generator voltage and are biased by generator current, Fig. 5-4. This transition differs from the earlier transition which was dependent primarily on generator voltage to initiate all forward transition steps and backward transition from shunting positions. Generator amperage was used for initiating backward transition from parallel.

Transition is used to initiate a change in motor connections so that full power may be obtained from the generator within its current and voltage limits. In addition to satisfying the above condition, E-I transition permits transition to take place at intermediate throttle positions assuming that the locomotive is traveling at or above transition speed.

Transition Relays -- Fig. 5-4

Transition can take place on a GP9 locomotive equipped with E-I type transition, assuming locomotive is at transition speed at throttle position 2 and above, resulting in a fairly constant KW output throughout the speed range of the locomotive for any given throttle position. At low generator current, the FSR and PTR relays pick up at a relatively low generator voltage and as the generator Current is increased, the relays pick up at a higher generator voltage, Fig. 5-5. In otherwords, the FSR and PTR relays operate at a fixed current - voltage ratio at the various throttle positions and KW levels.

Transition Relay Settings -- Fig. 5-5

505 Tracing Schematic Wiring Diagrams An understanding of how to trace a schematic wiring diagram would be helpful to anyone desiring a greater knowledge of the electrical operation of the Locomotive. It would also be valuable for purposes of trouble shooting when electrical difficulties arise.

The circuits that will be traced are those that are basic to the operation of the locomotive. They consist ofFuel Pump, Engine Starting, Reversing, Control and Excitation. Before tracing these circuits, certain electrical fundamentals should be understood which are as follows:

• 1. A complete circuit or path must exist before electricity will flow and perform a desired function. Thus starting from a source of electricity such as a battery or generator, current will flow through wires, switches and contacts providing that the path is uninterrupted backto the original source. The flow of electricity will be traced starting at the positive (+) side of a source and ending at the negative (-) side.
• 2. A contactor or relay will function when its associated operating coil is energized. Current flowing through such coils creates the magnetic force necessary to actuate the contacts. The contacts, which are a part of the contactor or relay will then open or close as the case may be, to make or break other electrical circuits.
• 3. Practically all contactors and relays are equipped with one or more secondary or auxiliary contacts which are called interlocks. These interlocks are actuated similar to the main contacts by means of energizing or de-energizing the operating coil and they function to make or break low voltage control circuits to achieve desired results.

These interlocks will be in their normal position either open or closed when the operating coil is not energized as shown in Fig. 5-6. When the coil is energized, they change position thus the normally open interlocks will close and the normally closed interlocks will open. When the coil is de-energized, the interlocks return to their previous normal position.

No Power To Coil Main contact normally open Interlock AB normally open Interlock CD normally closed	Power Applied To Coil Main contact now closed Normally open AB interlock now closed Normally closed CD interlock now open
Shown schematically on a wiring diagram, the normally open (N.O.) interlock is either below a horizontal line or to the right of a vertical line. The normally closed (N.C.) interlock is shown above or to the left side of a line.

Contact And Interlock Operation -- Fig. 5-6

• 4. All schematic wiring diagrams are drawn illustrating a "dead" locomotive with all switches open, control off and electrical contactors and relays de-energized. Thus all contacts and interlocks are shown in their normal position. such normal positionswill changeas the various contactors and relays are energized during the course of circuit tracing.

For simplification, the circuits to be traced have been taken from the complete locomotive schematic wiring diagram which is folded at the back of this manual. Also located at that point is a legend listing the abbreviations used for identifying electrical equipment and a chart of electrical symbols. It is advisable to become acquainted with this information before attempting to trace electrical circuits.

• A. Fuel Pump Circuit

  Referring to Fig. 5-7A, the fuel pump circuit may be traced as follows:

  Starting at the positive (ñ) side of the battery and by closing the main battery knife switch, current can 0 flow in the BP wire. A connection to this wire leads to the control knife switch which when closed allows current to flow to the 30-ampere control circuit breaker and control and fuel pump switches. When the circuit breaker is placed "ON" and the switch closed, current will flow through the PC wire which runs throughout the locomotive consist.

  Leading from the PC wire is a circuit to the fuel pump contactor coil (FPC) which will now be energized and results in closing the FPC contacts AB and CD. This circuit is completed by the N wire which leads through a 30-ampere negative control fuse to the negative (-) side of the battery.

  

  Fuel Pump Storage Battery 64 Volts And Engine Starting Circuits
  Fig. 5-7A

  Coming from the control switch is another circuit which leads to the 15-ampere fuel pump circuit breaker. When placed "ON" current will flow through it and closed FPC contacts AB and CD to the fuel pump motor. The motor should now run and the circuit tracing is complete.

• B. Engine Starting Circuit

  Referring to Fig. 5-7A the engine is started as follows:

  With current flowing through the PC wire (previously energized) a circuit leads to the isolation switch. When in the START position as shown, pressing the Start push button completes the circuit to the starting contactor coil (GS).

  The GS contacts will now close in the main generator circuit. This allows current to flow from the BP wire through the 400-ampere starting fuse, GS contact, main generator armature, gene rator field windings including the starting field and through another GS contact to complete the circuit at the N wire. The main generator now operates as a motor to crank and start the diesel engine.

• C. Reversing Circuit

  GP9 locomotives equipped with electro-magnetic reversing and power contactors have a somewhat different circuit arrangement than previous locomotives of this type. Basically this involves the use of local low voltage power from each unit to energize these devices since trainlining such circuits would result in excessive voltage drop. Trainlined circuits are still necessary to control these devices and cause them to pick up on the local control circuits provided. A description of this operation as it relates to the reversing circuit follows and is illustrated in Fig. 5-713.

  

  Reversing, Control And Excitation Circuits -- Fig. 5-7B

  From the previously energized PC wire, a circuit leads to the selector portion of the controller. With the lever placed in No. 1 position and the reverse lever in FORWARD, the current then flows in the FO trainline wire which runs throughout the locomotive consist. From this wire, a circuit energizes the forward pilot relay (FOR) which results in its contact FOR A-B closing in the reversing contactor circuit.

  The local control circuit is now established coming from the control knife switch through the 30-ampere local control fuse to energize the POA wire. Coming from the local control wire POA is a circuit which leads through normally closed interlocks RER G-H RVR4 C-D, RVR3 C-D and the now closed FOR A-B, through RVF1 and RVF2 A-B interlocks to energize the coils of the forward reversing contactors, RVF1 and RVF2. The main contacts of these contactors (not shown) close in the high voltage circuit to connect the traction motor for forward rotation.

  Operation in reverse is similarly accomplished but in this case the RE trainline wire is energized bringing in reverse pilot relay PER which in turn energized the reverse reversing contactor coils RVR3 I and JIVR4.

• D. Control Circuit

  Continuing with Fig. 5-7B, the control circuit to bring in the power contactors is as follows:

  With the isolation switch in Run position, the S13 power contactor picks up from local control wire POA through the now closed contacts and interlocks, FOR C-D, RVF1 E-F, RVF2 E-F, IS G-H and the normally closed interlocks GS A-B, P1 A-B and TR J-K.

  The S24 power contactor comes in from connection to the above circuit through P2 A-B. The main contacts of 513 and S24 (not shown) now close in the high voltage system connecting the traction motors to the main generator in a series-parallel circuit.

• E. Excitation Circuit

  With all the previous circuits established all that remains is to excite the main generator for power output. Referring to Fig. 5-7B this circuit is as follows:

  When the throttle is opened and the generator field switch closed, current will flow from the PC wire to energize the GF wire. The shunt field contactor (SF) now picks up from the GF wire through IS E-F, GP G-H, TR L-M, S13 G-H, S24 G-H, WS13 A-B and WS24 A-B.

  The battery field contactor (BF) picks up from connection to the preceding circuit through the now closed SF A-B and WSS A-B. With the main contacts of SF and BF now closed (not shown) the main generator puts out power and the locomotive is in motion.

506 Load Regulator Essentially the load regulator is an automatically operated rheostat connected in series with the battery field of the main generator.

The load regulator is a self contained unit which consists of a hydraulic vane type motor connected to a commutator type rheostat, Fig. 5-8. Engine oil pressure used to force the vane motor (and rheostat brusharm) to vary its position. Oil pressure is impressed on either side of the vane, as directed by the load regulator pilot valve, which is located in the engine governor.

For the purpose of load regulation, engine horsepower is determined by the rate of fuel consumption; this merely means that , more horsepower is developed when more fuel is used, and vice versa. There is a definite rate of fuel consumption for each throttle position when the engine is loaded. The rate of fuel consumption is related to the position of the governor power piston, which controls the opening of the injector racks. If the load on the engine should be such that more fuel is dem anded (to rotate the engine the RPM "ordered~' by the throttle) than the predetermined balance point (between load and fuel consumption), the load regulator pilot valve will cause the load regulator to reduce the engine load the required amount by reducing the battery field strength.

If the engine requires less fuel than the predetermined setting, the load regulator increases the load on the engine by increasing the battery field excitation of the main generator. In this manner, battery voltage, temperature changes in the generator windings, or locomotive speeds do not cause overloading or underloading of the engine and a constant power output is maintained for each throttle setting.

Located in the governor is an overriding solenoid, ORS, which can override the normal action of the load W regulator pilot valve. When the ORS is energized it forces the load regulator pilot valve to cause engine oil pressure to move the load regulator toward the minimum field position unloading the engine. The ORS is energized during transition and wheel slip action. The governor is also equipped with two microswitches, LRS and OLS, which protect against possible engine overload. The switches are set to close when a predetermined high rate of fuel consumption is reached. When the LRS switch closes, the "quick starting" feature of the GP9 is cut out, and the control of engine loading is returned to the load regulator. (The "quick starting" feature is effective only in transition 1.) When the OLS switch closes, the ORS is energized moving the load regulator toward the minimum field position, reducing the load on the engine.

507 Engine Speed Control The throttle lever, in the controller, has ten positions: STOP, IDLE and RUNNING SPEEDS 1 THROUGH 8. Each throttle step, 0 from 2 through 8, increases the engine speed 80 RPM.

The throttle lever operates a phenolic cam which controls enclosed roller switches to distribute current from a "hot wire" to one or more other wires, depending on the position of the throttle.

The governor is designed so that the energizing of various combinations of four governor solenoids (AV, By, CV, and DV) causes the engine to respond to the "orders" of the throttle. The "ENGINE SPEED CHART" shows the various combinations of solenoids that are energized to obtain the desired engine speeds for the various throttle positions. The Engine Speed Control schematic diagram, Fig. 5-9, shows the method of energizing the governor solenoids for the various positions of the throttle.

ENGINE SPEED CHART

Engine Speed Control -- Fig. 5-9

508 ER Relay The ER relay controls the current supply to the A, B, and C governor control solenoids. De-energizing this relay will cause the engine to immediately stop if the throttle is in Run 5 or 6. De-energizing the ER relay in any other throttle position will bring the engine to idle.

To control the engine speed in any unit the ER relay in that unit must be energized. The ER relay has three normally open interlocks which will close, when the relay is energized, to connect the control circuits to the A, B, and C governor control solenoids, Fig. 5-9. The ER relay has no control of the D governor control solenoid.

The ER relay in each unit is energized by current received from the FP wire that runs throughout the locomotive. For current to flow through the FP wire to the ER relay: the main battery and control knife switches must be closed, the "Engine Run" switch at the engineman's control panel must be on, the "PC" switch must be closed, the isolation switch must be in RUN, the NVR relay must be energized (engine must be running), and the ground relay must be set.

Battery Field Contactor -- Fig. 5-10

509 Battery Field Contactor and Fuse When the throttle is moved from Idle toRun 1,this contactor closes and connects low voltage excitation to the main generator battery field. The battery field contactor, Fig. 5-10, remains closed as long as power is being applied, but will open during transition and wheel slip action. A rectifier and discharge resistor are used to dissipate the high voltage induced in the batery field when the battery field contactor is opened. An 80 ampere battery field fuse located in the elecrical cabinet protects the battery field circuit. If the use is blown the locomotive will not develop normal power.

510 Wheel Slip Control The wheel slip control system goes into opŠr tion the moment that he slipping of a pair of wheels is detected while under ower. Located in the electrical cabinet are four wheel slip control relays, WS13, WS24, WSS and WCR. Each relay is of the through-cable type, Fig. 5-11.

The WS 13-24 relays are operated by two sources; (1) By a flow of current through the relay coil with the traction motors connected in series-parallel or series-parallel shunt. Current will flow through the relay coil when an unbalance in the bridge circuit between two 2000 ohm resistors and two traction motors, which the relay coil bridges, occurs as a result of a "slipping" motor. (2) By a current differential between the cables that pass through the relay frame with the traction motors connected in parallel or parallel-shunt. These cables are so arranged that the normal current flow through them is of equal magnitude and in opposite directions. Thus, the magnetic field established by the current flow in one cable is nullified by the magnetic field established by the current flow in the second cable. When an unbalance in the current flows occurs as a result of a "slipping" motor, the resultant magnetic field established actuates the WS relay.

Wheel Slip Relay -- Fig. 5-11

The WCR (wheel creep relay) and WSS (wheel slip series) are operated only by a current differential between the cables that pass through the relay frame, with the traction motors connected in series-parallel or series-parallel shunt.

Automatic sanding in power occurs through the action of the WCR relay. The WCR is used to detect very slow creeping type slips. The function of the WCR, having a slightly lower pickup value than the WSS and WS relays, is to automatically apply sand to the rails which tends to prevent a wheel slippage necessitating the reduction of generator field excitation.

When WCR picks up, it energizes the time delay sanding relay (TDS). "Picking up" of the TDS automatically actuates the forward or reverse sanding valves, depending on the position of the reverse lever, applying sand to the rail.

At very slow speeds, if the wheel slip cannot be corrected through the action of the WCR applying sand to the rails, the WSS picks up to reduce main generator excitation. When the WSS picks up, the wheel slip light will flash ON and the battery field contactor (BF) will open. Opening the battery field contactor "cuts out" the main generator battery field excitation and causes the0 overriding solenoid (ORS) to move the load regulator toward the minimum field position. This action will generally correct the wheel slip, and it should not be necessary for the engineman to reduce the throttle. The function of the WSS relay is to recognize slow speed wheel slips and effect a slip correction with a minimum loss of tractive effort.

If further reduction of main generator excitation is necessary to correct wheel slip, the WS relay, actuated by a current flow through the relay coil, picks up and opens both the battery and shunt field contactors, reducing the excitation of the main generator to a point where slipping stops. The time delay sanding valve (TDS) is energized, automatically applying sand to the rails. When the shunt field contactor opens, an additional resistance is added into the shunt field circuit resulting in a further but controlled unloading of the main generator. Opening the battery field contactor, energizes the ORS, and the load regulator moves toward the minimum field position. Thus as soon as the slipping stops, the WS relay will drop out, and power will automatically be reapplled at a lower level than that at which the slipping was initiated. The application of power will then gradiually return to that designated by the position of the throttle.

To correct high speed wheel slips with the traction motors connected in parallel or parallel shunt, either of the WS relays actuated by a current differential between traction motors 1 and 3 (WS 13) or 2 and 4 (WS 24) will pick up to reduce main generator excitation to a point where slipping stops.

Since sand is automatically applied to the rails during a wheel slip detection, it should be unnecessary for the engineman to operate the manual sanders. If continuous wheel slipping on sand occurs, the throttle should be reduced.

511 Battery Switch This switch, Fig. 5-12, is located in the electrical cabinet and connects the battery to Lhe low voltage circuits. Battery Switch Panel ro start the Diesel engine, and during normal locomotive operation, the main battery switch should be closed.	Battery Switch Panel -- Fig. 5-12

512 Battery Ammeter The battery ammeter, located on the rear cab wall, shows whether the battery is charging or discharging. Normally the meter will indicate zero or a slight charge. If ammeter shows a continual discharge, the auxiliary generator output should be checked or the battery may run down.

RCR -- Micropositioner -- Fig. 5-13	513 Reverse Current Relay The reverse current relay, RCR, is shown in Fig. 5-13. The purpose of the RCR is to prevent a flow of battery current from motorizing the auxiliary generator. To prevent this, the reverse current relay opens the battery charging contactor whenever the auxiliary generator voltage drops below the battery voltage.

514 Battery Charging Contactor (BC) The battery charging contactor is an electrically operated switch which connects the auxiliary generator output to the low voltage system. The reverse current relay controls the operation of the battery charging contactor.

515 Ground Relay The ground relay, Fig. 5-14, is located on the cab side of the locomotive high voltage cabinet. The function of the ground relay is to automatically unload the main generator in case of a ground in the high voltage system. A ground can be defined as current passing through the frame or carbody of the locomotive.

If a ground in the high voltage system should occur, the ground relay will trip, opening the shunt and battery field contactors, unloading the main generator. The ground relay must be reset before the unit can again deliver power. The relay is reset by pressing in on the reset button on the rear cab wall. Should the relay repeatedly trip when power is applied, the power plant MUST be isolated.	Ground Relay -- Fig. 5-14

CAUTION: Isolate unit before resetting ground relay.

If a ground relay trips, the "White" alarm light the engineman's control station will come on and the alarm bell will ring. The relay must be reset to silence the bell and extinguish the light.

With the ground relay tripped, the speed of the engine will be automatically reduced to Idle. If the ground relay tripped while the throttle was in the 5th or 6th notch, the engine would stop.

Although a high voltage ground will normally be the only reason for the ground relay tripping, a low voltage ground can trip the relay when the engine is started; since at that time the high and low voltage systems are temporarily connected. Ground relay action is not necessarily an indication of serious trouble but should reported to the maintenance authorities.

The ground relay knife switch, when open, eliminates the protection of the ground relay. This switch MUST NOT BE OPENED in normal operation unless definite instructions are issued by a railroad official.

516 Voltage Regulator The voltage regulator, Fig. 5-15, is located in the electrical cabinet on the engine room side. The voltage regulator performs the function of seeing that the output voltage of the auxiliary generator remains at approximately 74 volts whenever engine is running.	Voltage Regulator -- Fig. 5-15

517 Auxiliary Generator Fuse (Battery Voltage Regulator Charging) This 150 ampere fuse (250 amperes if locomotive is equipped with steam generator), located In the electrical cabinet, Fig. 5-12, protects the auxiliary generator against any possible overload. If the auxiliary generator output fuse should become blown it will cut off the auxiliary generator from the low voltage system and alternating current system. The ammeter will indicate a discharge when the auxiliary generator output fuse is blown, the alarm bell will ring, and the "Alternator Failure" light (blue) will be ON in the unit affected.

518 Auxiliary Generator Field Circuit Breaker This 30-ampere circuit breaker located on the rear cab wall, Fig. 5-16, protects the auxiliary generator field windings against excessive current. The "tripping" of this circuit breaker will prevent the auxiliary generator from supplying current to the low voltage system and the alternating current system. With the auxiliary generator circuit breaker "tripped" the battery ammeter will indicate a discharge, the alarm bell will ring, and the "Alternator Failure" light (blue) will be ON in the unit affected.

Circuit Breakers Rear Cab Wall Fig. 5-16

519 Alternator Field Circuit Breaker This 30-ampere circuit breaker, located on rear cab wall, Fig. 5-16, protects the alternator field windings against possible overload. The "tripping" of this circuit breaker will shut off the supply of AC current to the traction motor blowers and radiator cooling fans. When this circuit breaker trips open, the alarm bell will ring and the blue "Alternator Failure" light will be ON in the unit affected.

520 No AC Voltage Relay As the traction motors are cooled by AC driven blowers, failure of the alternator could result in damage to the traction motors unless the application of power was stopped. Thus, in case of an alternator failure, the NVR, Fig. 5-17, located in the cab side of the electrical cabinet, drops out and causes the alarm bell to ring in all units. The "Alternator Failure" light (blue) will be on, and the engine speed reduced to idle in the unit affected (if the throttle was in the 5th or 6th notch the engine would stop). The NVR "dropping out" can be caused by (1) "Auxiliary Generator Field" or "Alternator Field" circuit breaker tripped open (2) Auxiliary generator fuse blown or (3) Diesel Engine stopped while "on the line."

NVR Relay - Fig. 5-17

High Voltage Cabinet - Cab Side
Fig. 5-18

High Voltage Cabinet - Engine Room Side
Fig. 5-19

LEGEND OF ELECTRICAL EQUIPMENT

The following list shows abbreviations identifying electrical equipment on the locomotive and/or the wiring diagrams. The diagram wire designations conform with the identification bands on the wires in the locomotive.

The diagram shows the contactors, switches and relays as if the engine was stopped and all manual switches open. It must be remembered that when the operating coil of a contactor becomes energized the contacts and interlocks associated with that contactor will then be in a position opposite to that shown in the wiring diagram.

AC1, AC2	Radiator Cooling Fan Contactors
AV	Governor Speed Solenoid + 80 RPM
AWS	Auxiliary Wheel Slip Relay
BC	Battery Charging Contactor
BF	Battery Field Contactor
BKB	Dynamic Braking Contactor
BKP1, BKP2	Dynamic Braking Contactors
BK	Dynamic Braking Contactor
BR	Dynamic Braking Relay
BV	Governor Speed Solenoid + 320 RPM
BWR	Brake Warning Relay
CC	Compressor Control Magnet Valve
CCS	Compressor Control Switch
CR	Compressor Control Relay
DV	Governor Speed Solenoid - 80 RPM
DBR	Dynamic Brake Regulator
ER	Engine (Speed Control) Relay
ETS	Engine Temperature Alarm
FPC	Switch Fuel Pump Contactor
FS	Motor Field Shunting Contactor
FSV	Forward Sanding Valve
FSR	Transition Relay - Field Shunting
FSD	Field Shunt Delay Relay
GFR	Generator Field Relay
GR	Ground Relay
CV	Governor Speed Solenoid + 160 RPM
GS	Generator (Engine) Starting Contactor
IS	Isolation Switch
LOS	Low Oil Pressure Switch
LRC	Load Regulator Contactor
LRP	Load Regulator Positioner
OLS	Governor Overload Switch
ORS	Governor Over-riding Solenoid
P1, P2, P3, P4	Parallel Power Contactors
PCR	Pneumatic Control Relay
PCS	Pneumatic Control Switch
PTR	Parallel Transition Relay
RCR	Reverse Current Relay
FOR	Forward Pilot Relay
RER	Reverse Pilot Relay
RVF1, RVF2	Forward Reversing Contactors
RVR3, RVR4	Reverse Reversing Contactors
S13, S24	Series Power Contactors
SF	Shunt Field Contactor
SFT	Shunt Field Transfer Relay
SMV1, SMV2	Shutter Magnet Valves
RSV	Reverse Sanding
TDS	Valve Time Delay Sanding
TA, TB	Relay Temperature Control Switches
WCR	Wheel Creep Relay
WSS	Wheel Slip Series Relay
WS13, WS24	Wheel Slip Relays
FL	Field Loop Contactor
TR	Transition Relay

ELECTRICAL SYMBOLS

Electrical Diagram - Dynamic Brake Equipped

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