Usage:
4.1 Basic Excitation System
FIGURE 4
FIG 4 shows the original excitation system in the locomotive and the modules that are to be removed.
FIG 4 also shows how the CATERPILLAR LOCOMOTIVE GOVERNOR hardware integrates into the locomotive's excitation system after the modules and load regulator are removed.
4.2 Dynamic Brake System
FIGURE 5
FIG 5 shows how the dynamic brake system ties into the original excitation system in the locomotive.
FIG 5 also shows how the dynamic brake system ties into the CATERPILLAR LOCOMOTIVE GOVERNOR system. The feedback signal for the DR module (that originates from the RC module in the original system) is now sourced from the CATERPILLAR LOCOMOTIVE governor connection TB392 L12. The control software contains a filter that duplicates the action of the RC module.
4.3 Wheel Slip System
A standard WS 10 wheel slip control system provides 5 combinations of 5 response actions in SD 40-2 and SD 45-2 locomotives. Each combination of responses is initiated when a particular condition is detected by the wheelslip system. Table 2 identifies these responses, and the conditions.
Responses 1, 2 and 3 require no analog interface with the governor system.
Responses 4 and 5 do require an analog interface with the governor system and FIG 6 shows how this is achieved in the original excitation system of the locomotive.
Since the RC module is eliminated with the CATERPILLAR LOCOMOTIVE GOVERNOR system, response 1 no longer applies. The locomotive wiring is therefore modified to activate response 2 (which is essentially a generator unload signal) with combinations 2, 3 and 4. The CATERPILLAR LOCOMOTIVE GOVERNOR system is programmed with ramp rates to emulate the performance of an RC discharge (and recovery) and load regulator reset (and recovery) in response to a generator unload signal.
FIGURE 6
FIG 6 also shows how responses 4 and 5 are achieved with the CATERPILLAR LOCOMOTIVE GOVERNOR system.
4.4 Excitation Limit
In the original locomotive system a limit was imposed on the maximum voltage available out of the load regulator to the SB module, this limit was different for each notch position, and can also depend on the status of the motor cutout relay if fitted. In the CATERPILLAR LOCOMOTIVE GOVERNOR system, these limits are defined in software, TABLE 1 contains standard values for both sets of limits.
The digital input from the motor cutout relay determines which set of values in the table are active.
FIGURE 7
Figures 7 shows simplified block diagrams of the Pacesetter interface to both of the excitation systems. With the CATERPILLAR LOCOMOTIVE GOVERNOR system the Pacesetter output voltage is connected to the dynamic brake analog input channel on the derate module.
- 1. In normal mode, ie. no dynamic brakes and no Pacesetter, this input is tied high, ie. greater than 50 volts (see FIG 2B).
- 2. If the dynamic brakes are not active and the Pacesetter is switched on, the Pacesetter output is connected to this input channel and determines the excitation limit when it is lower than the normal limit from the active table. This condition should be satisfied since the normal procedure when using Pacesetter is to initially set the notch lever to a much higher power setting than is required for the pacesetter speed setting.
- 3. When dynamic brakes are active, this analog input is connected to the dynamic brake signal and determines the excitation signal as it did in the original locomotive system.
- 4. In dynamic brake mode, this input signal is filtered in the software of the CATERPILLAR LOCOMOTIVE GOVERNOR (this filtering is one of the functions of the removed RC module).
- 2. If the dynamic brakes are not active and the Pacesetter is switched on, the Pacesetter output is connected to this input channel and determines the excitation limit when it is lower than the normal limit from the active table. This condition should be satisfied since the normal procedure when using Pacesetter is to initially set the notch lever to a much higher power setting than is required for the pacesetter speed setting.
On some locomotive installations the Pacesetter signal is injected into the excitation system via the RC module in which case it will be filtered by the RC module and therefore will require software filtering by the CATERPILLAR LOCOMOTIVE GOVERNOR.
On other locomotive installations the Pacesetter signal is injected into the excitation system directly into the load regulator via a separate filter in which case it will not be filtered by the software of the CATERPILLAR LOCOMOTIVE GOVERNOR.
The locomotive operator must specify this filter requirement.
4.5 Notch Settings
Table 1 shows standard settings for the different notch lever positions. These include:
- 1 Engine speeds.
- 2 Rack settings.
- 3 Traction KW settings.
- 4 Voltage limit settings.
- 5 Current limit settings.
- 6 Excitation limit settings.
- 7 Nominal traction horsepower.
- 2 Rack settings.
3612 Repower Notch Settings
TABLE 1
Wheelslip Responses
TABLE 2