Usage:
2.1: Personality Module Settings
The functions performed by the electronic governor system are defined in the personality module of the governor. The functions that are unique to a particular application have unique settings defined in the personality module (engine type and power, number of axles, with or without dynamic brakes, etc). Each combination of settings requires a unique part number for its associated personality module.
Each application has a unique personality module part number associated with it. Refer to 3500 Locomotive Engines Personality Module Settings, SENR5187 for a complete listing of the different personality modules with their respective settings. For certain types of tests (engine load versus notch) reference must be made to SENR5187.
There are other software packages available for this electronic governor system for a variety of locomotive and non-locomotive applications. This manual is only compatible with those personality modules listed in SENR5187.
The electronic governor system employs an isochronous engine speed governing algorithm using a PID control loop. The desired engine speed is defined by a four digit notch code. There is a desired engine speed setting for each code.
This system can use all 16 available notch codes if needed. It is normally programmed with 10 codes (eight power settings, low idle and shutdown). The speed feedback for this function is obtained from an engine mounted speed sensor.
2.2.1: Dual Ramp Rate/Transition
The electronic governor system can be set up with a dual engine speed ramp rate (and no series parallel/parallel traction motor transition) or for series parallel/parallel traction motor transition (and only one engine speed ramp rate).
The dual ramp rate set up is intended for use on locomotives that will be used for switch-yard service and will normally be four axle locomotives that do not require transition with the standard Caterpillar engine/alternator packages.
The transition set up is intended for use on six axle locomotives that are typically main-line or branch-line locomotives not used in switch-yard service.
2.2.2: Fuel Rack Limiting During Engine Start
The engine speed governing algorithm is modified while the engine is being started to limit the maximum rack position. This feature limits smoke during an engine start.
2.2.3: Dual Engine Speed In Dynamic Brake Mode
In dynamic brake mode the power requirements on the engine are minimal and for best fuel consumption, the engine speed in this mode would normally be at idle. On most DC-drive locomotives the cooling air flow to the traction motors is a function of the engine speed. At high levels of dynamic braking, the traction motors require more cooling air than idle engine speed provides.
The electronic governor system provides for two engine speeds in dynamic brake mode. Which speed is selected is a function of the signal level on the 24T trainline (a function of the position of the dynamic brake lever position).
The two engine speeds and the 24T signal trip points are defined in the personality module.
2.3: Generator Excitation Control Functions
There are three primary modes of excitation control:
- * Motoring Mode
- * Load Test Mode
- * Dynamic Brake (DB) Mode
- * Load Test Mode
This is the most complex mode. Within this primary mode there are two subsidiary modes:
- * Closed Loop Traction Power Mode
- * Closed Loop Gross Engine Power Mode
Traction Power Mode
The generator exciter drive current is modulated to give a fixed traction power to the wheels for a given notch. The feedback (measured traction power) for this control loop is obtained from generator voltage and generator current feedback signals to the electronic governor.
The notches this mode are active in plus the power settings for each of these notches are defined in the personality module.
Gross Engine Power Mode
The generator exciter drive current is modulated to give a fixed gross engine power for a given notch. The feedback (measured engine power) for this control loop is obtained from a rack position feedback sensor mounted on the engine. This mode relies on the fact that the engine speed governor algorithm is isochronous and for a given rack position the engine power will be constant.
The control loop in this mode modulates the exciter drive current so that the engine's rack position stays at a fixed value for a given notch.
The notches this mode are active in plus the rack position settings for each of these notches is defined in the personality module.
The following power derate functions can override and reduce engine power in the GROSS ENGINE POWER MODE only:
- * High Coolant Temperature Derate
- * Low Barometric Pressure Derate
High Coolant Temperature Derate
This function reduces the rack setting for each of the notches as a function of coolant temperature. The coolant temperature is measured in the coolant line after the water pump and before the aftercooler. The coolant at this point is at a temperature that results from a mixing of the thermostat bypass flow and the radiator outlet flow.
When the temperature exceeds a certain set point, this function generates a bias signal (in software) that is a linear function of the amount that the temperature exceeds the set point (it is limited to a specific value). This bias signal is then subtracted from the normal rack setting for the particular notch reducing the engine power.
When this function is active the main electronic governor system annunciates this with an LED display on the front face of the main electronic governor box.
The values for the temperature set point, the linear gain and the bias limit are defined in the personality module.
Low Barometric Pressure Derate
This function reduces the rack setting for each of the notches as a function of barometric pressure. The pressure is measured at the engine air inlet downstream of the air filters. This function will be active with blocked air filters.
When the pressure drops below a certain set point, this function generates a bias signal (in software) that is a linear function of the amount that the pressure is below the set point (it is limited to a specific value). This bias signal is then subtracted from the normal rack setting for the particular notch reducing the engine power.
When this function is active the main electronic governor system annunciates this with an LED display on the front face of the main electronic governor box.
The values for the pressure set point, the linear gain and the bias limit are defined in the personality module.
NOTE: The following power derate functions can override and reduce engine power in both GROSS ENGINE and TRACTION POWER MODES. These functions work on a "low wins" basis (whichever function requires the lowest exciter current will be the function that defines the exciter drive current).
These functions are:
- * Generator Voltage Limiting
- * Generator Current Limiting
- * Traction Motor Current Limiting
- * Traction Motor Current Matching (Performance Control)
- * Pacesetter Compatibility
- * Differential Wheelslip Regulation
- * Synchronous Wheelslip Regulation
- * Generator Current Limiting
Generator Voltage Limiting
This function reduces the exciter drive current level (from that determined by one of the POWER CONTROL MODES) to regulate the generator voltage to a specific value for each notch. These values are defined in the personality module.
This function uses a "generator voltage feedback" signal.
Generator Current Limiting
This function reduces the exciter drive current level (from that determined by one of the POWER CONTROL MODES) to regulate the generator current to a specific value for each notch. These values are defined in the personality module.
This function uses a "generator current feedback" signal.
Traction Motor Current Limiting
This function reduces the exciter drive current level (from that determined by one of the POWER CONTROL MODES) to regulate the traction motor current to a specific value for each notch. These values are defined in the personality module.
This function uses one of two traction motor current feedback signals. One represents the value of the highest motor current and is used by this function. The other represents the value of the lowest motor current.
Traction Motor Current Matching (Performance Control)
This function reduces the traction motor current limit as a function of the traction motor voltage.
This function is defined in the personality module.
Pacesetter Compatibility
The electronic governor system is compatible with a pacesetter system. This works through the traction motor current matching function. Refer to 3500 Locomotive Engines Personality Module Settings, SENR5187, for an explanation of this function.
Differential And Synchronous Wheelslip
The electronic governing system contains two strategies for detecting and regulating wheelslip. Refer to "2.4: Wheelslip Strategies" in this manual for a more detailed explanation of the wheelslip control strategies.
This mode is basically the same as the "MOTORING MODE" except:
- * Traction motor current limiting disabled
- * Traction motor current matching disabled
- * Differential wheelslip regulation disabled
- * Synchronous wheelslip regulation disabled
- * Reduced generator current limit
- * Traction motor current matching disabled
Excitation is disabled for a defect on either the generator voltage or the generator current feedback signals.
This mode has two primary functions in the excitation control loops. These two functions also work on a "low wins" basis (whichever function requires the lowest exciter current will be the function that defines the exciter drive current). The two functions are:
- * Grid Current Regulation
- * Field Current Regulation
Grid Current Regulation
This function modulates the exciter drive current to regulate the dynamic brake grid current to a value that is a function of the signal level on the 24T trainline. This signal represents the position of the dynamic brake lever which is set by the locomotive operator. This control loop uses two grid current feedback signals that represent the value of the highest grid current and the value of the lowest grid current.
The overall loop gain of the grid regulation loop changes over a wide range with locomotive ground speed. This regulation loop uses an adaptive algorithm that adapts to the changing ground speed. This results in stable and responsive regulation performance at all ground speeds.
The function that relates the grid current level to the 24T signal is defined in the personality module.
Field Current Regulation
This function modulates the exciter drive current to regulate the motor field current to a value that is a function of the signal level on the 24T trainline. This control loop uses the generator current feedback signal.
The function that relates the field current level to the 24T signal is defined in the personality module.
When too much power is fed to the traction motors the wheels will spin. In the following discussions the term "wheelslip" is used to describe when the wheels just start to spin, but have not yet reached a high enough speed to cause damage to the rails and wheels.
Wheelslip can occur in two ways; single axle slip (differential wheelslip) and multiple axle slip (synchronous wheelslip). The electronic locomotive control system can detect both types of wheelslip and automatically reduce the power fed to the traction motors and thus eliminate the wheelslip.
This requires no corrective action on the part of the locomotive operator. The throttle can be left in notch 8, even with wet or oily track conditions.
The electronic locomotive control system automatically triggers the locomotive's sanders when either type of wheelslip is detected. The electronic locomotive control system drives the sanders via an interface relay.
The relay is energized 200 milliseconds after a wheelslip condition is first detected (if it prevails for 200 milliseconds).
The relay is then cycled (one second on and one second off) until all wheelslip conditions have been corrected.
If an excessive (beyond normal regulation range) wheelslip occurs, the relay is energized continuously until this condition is corrected. This is an abnormal condition which could be caused by a slipping pinion. The excitation current is set to zero and it is annunciated by a diagnostic code on the LED's on the front panel of the main electronic governor box.
NOTE: The trainline wheelslip signal can be triggered by a time delay relay driven from the electronic governor system's relay. It is recommended that a 1.5 second delay is used so that the trainline signal is not triggered during normal wheelslip regulation, but only when an excessive wheelslip condition has prevailed for more than approximately one second.
2.4.3: Synchronous Wheelslip (Motoring Only)
The axle speed and acceleration are derived from the current and voltage feedback signals. The inferred speed is used as a feedback to regulate the speed of the slipping axles so the axles never spin fast enough to cause any damage.
2.4.4: Differential Wheelslip (Motoring And Braking)
Differential wheelslip is detected by comparing the highest and lowest traction motor (or grid) currents. When the difference is excessive the locomotive electronic control system automatically reduces the current fed to the traction motors (or field current in the case of DB) and stops the slip.
The method of detection has the following advantages:
- * It is not affected by the normal tolerances in the current measuring circuits.
- * It is not affected by the differences in wheel diameters.
- * In motoring mode it functions properly with any number of motors cutout and allows full current to the remaining motors.
- * It is not affected by the differences in wheel diameters.
Both the synchronous and the differential wheelslip control loops provide smooth changes in tractive effort which protects the draft gear from heavy shock loads.
The electronic governor system includes two alarms associated with the dynamic brake grids. These two alarms are:
- * Grid Over Current Alarm
- * Grid Cooling Fan Alarm
These functions are performed by circuits within the wheelslip module and drive relays. The functions are not accessed by the main system software. The electronic governor system has no programmed response to either of these alarm conditions. These alarms have been provided because the electronic governor system has access to the necessary feedback signals to detect them. The rebuilder can use them in whatever manner is consistent with the requirements of the final customer of the locomotive.
These functions can be enabled or disabled. Refer to "4.9.3: Electronic Governing System" for details of the wiring for these functions.
In motoring mode the electronic governing system can accommodate any number of motors cutout. With a motor cutout, the motor current limits will remain unchanged. The net effect is that at low ground speeds the engine will produce less power for a given ground speed. Full rated engine horse power will still be attainable, but at a higher ground speed.
The wheelslip module is equipped with a specific motor cutout input for each of its six motor current analog inputs. These motor cutout inputs can be considered as an enable/disable signal for each of the motor current analog inputs.
Dynamic brake mode is normally disabled by the locomotive's electrical system if a motor is cutout.
Refer to "4.9.3: Electronic Governing System" for details of the motor cutout wiring.
2.7.1: Diagnostic Code In Electronic Governor
The electronic governing system has a comprehensive set of diagnostic strategies to detect failure conditions and respond accordingly to protect the engine. Each fault condition is displayed by an LED code on the front face of the main electronic governor box.
The following fault conditions will shut the engine down:
- * Failed Speed Sensor
- * Failed Personality Module
- * Failed Main Governor Box
- * Failed Personality Module
The following two fault conditions are also detected and displayed:
- * High Rack Slew Rate
- * Stuck Rack Linkage Or Actuator
No response is programmed into the system. Each fault condition will result in abnormal behavior, and the displayed diagnostic code should assist the maintenance personnel in correcting the problem.
The "Failed Rack Position Sensor or Sensor Harness" fault condition is detected, displayed and also accompanied by a programmed response.
The response to this defect will allow the gross engine power mode to continue to provide reasonably correct engine horse powers in each notch. The discrepancy will depend on how long the locomotive has been "on duty" providing power since the last time the electronic governor system was de-energized. The governor system generates an inferred rack position (from the rack actuator drive current) by measuring the correlation between rack actuator drive current and rack position. Until the system has had an opportunity to generate a sufficiently large data base, this correlation will be inaccurate and is deliberately set to give low rather than high powers.
The temperature signal of the linear coolant temperature derate function of the electronic governor system is shorted to battery negative. This will set the linear coolant temperature derate function to maximum derate. The temperature trip point is set high enough to ensure it will only be active in the event of a failure in the linear derate temperature sensor.
2.7.3: Start And Emergency Shutdown Logic
The bulk of this system is defined by the relay logic. Since the equipment is housed in a ship loose junction box, some of the logic is also defined by customer wiring in the locomotive. Wiring details are covered in the Installation section of this manual.
The main features are as follows:
- * Starter motor engagement is inhibited while the engine is rotating.
- * Starter motors are automatically disengaged at a predetermined speed.
- * Start is aborted and the engine shuts down if the start pushbutton is released before the engine reaches starter cutout speed.
- * Auxiliary alternator and generator are both at zero excitation until the engine reaches starter cutout speed.
- * Following start up there is a nine second grace period for the oil pressure to build up.
- * Following start up there is a nine second grace period for the auxiliary generator to start charging the battery.
- * The excitation to the auxiliary generator is set to zero following any engine shutdown.
- * Engine is shut down in the event of a failure of the overspeed switch speed sensor.
- * Any shutdown condition (emergency or otherwise) is latched and cannot be cleared until the engine stops rotating.
- * Starter motors are automatically disengaged at a predetermined speed.
2.8: Traction System Protection
The large number of electronic governing system functions are performed with very few traction feedback signals. The feedback signals are:
- * Generator Voltage
- * Generator Current
- * Highest Traction Motor/Grid Current
- * Lowest Traction Motor/Grid Current
- * Generator Current
Failure of one signal can adversely affect several key functions. It is important that a failure of a feedback signal be detected and responded to quickly.
The electronic governing system has detection strategies for each of the traction feedback signals to detect an open circuit connection or a short circuit to battery positive (+) or battery negative (-).
The response strategies are covered in detail in the Troubleshooting section of this manual.
Single failures are tolerated by reducing either the generator current limit or the traction motor current limit to a safe level. Each combination of multiple failures are also treated in a fail-safe manner. Multiple failures set the exciter drive current to zero.