795F AC Off-Highway Truck Electric: Electric Power Generation : Generator Control and Operation

Generator Exciter Field Regulator (EFR)

Generator Exciter Field Regulator connections

The Generator Excitation Field Regulator located under the Generator on the air duct. The left-hand 14 contact control circuit connector and the right-hand 4 contact exciter circuit harness connector.

The Drivetrain ECM will use the EFR to control the operation of the Generator. The EFR is mounted on the top side of the cooling air duct under the Generator.

The Drivetrain ECM will send PWM duty cycle current command signals to the EFR. The ECM command signals will determine the amount of electrical current that the EFR will send to the Generator exciter winding. The PWM duty cycle range that the ECM will use for the current command circuit is 5 percent to 95 percent.

Based on these signals, the EFR will send a 0.0 amp to 20.0 amp DC electrical current to the exciter stator windings. A 5 percent signal would result in less than 1.0 amp of current being sent to the exciter stator windings and a low Generator output. A duty cycle of 95 percent will result in 20.0 amp of current being sent to the exciter stator windings and a high Generator output.

The level of electrical current that the EFR sends to the exciter stator windings affects the stator magnetic fields. A stronger exciter stator magnetic field results in a greater Generator output.

When a low electrical current or no electrical current is being sent to the exciter stator windings by the EFR, the Generator will produce a small output level of "residual voltage " of approximately 75 VAC or less.

The EFR DC current output that is sent to the exciter stator windings and the rotation speed of the Generator will determine the level of Generator output voltage and current that will be supplied to the Inverter DC Power Bus.

To provide the power to supply the output electrical current, the EFR receives a 24.0 VDC system control power through a 40.0 amps circuit breaker. The EFR "boosts" the system voltage to 144.0 VDC. This voltage is the EFR output voltage on the exciter (+) and exciter (-) circuits that are connected to the Exciter Stator windings. Capacitors are used for this process.

After machine shutdown, the exciter current circuits can contain hazardous voltage levels for approximately five minutes as the capacitive voltage is discharged. If service is required on the EFR, wait for at least five minutes after Engine shutdown before disconnecting the four contact exciter circuit connectors. In addition, wait for at least five minutes before entering the Generator auxiliary connection enclosure. Always use a multimeter to verify that there is 50.0 VDC or less at any exposed exciter circuit contacts before any other action is taken.

The Drivetrain ECM will control the operation of the Generator based on operator control inputs, the speed status of the traction motors and communication from the two motor control ECMs.

During machine operation, the EFR monitors the internal control circuits and monitors the level of output current that is being sent to the exciter stator windings. The EFR will use two PWM feedback circuits that are connected to the Drivetrain ECM to indicate the EFR operational status.

The Drivetrain ECM will use the 5.0 VDC sensor power supply to provide the power supply for both of the PWM feedback circuits.

The EFR will use a PWM duty cycle signal on a dedicated current feedback circuit in order to provide an indication of the level of output current that is being sent to the exciter stator winding.

The acceptable PWM duty cycle range of the current feedback signal is 3 percent to 97 percent. The duty cycle will correspond to the 0.0 amp to 20.0 amp EFR current output.

If an abnormal condition is detected, the EFR will use a diagnostic feedback circuit to send a PWM duty cycle signal to the Drivetrain ECM. The percentage of the PWM duty cycle is used to indicate different fault conditions that the EFR has detected to the Drivetrain ECM.

The following table lists the PWM duty cycle signals that the EFR will use for diagnostic feedback and the indications to the Drivetrain ECM:

Table 1

EFR Diagnostic Feedback PWM Signals
PWM Duty Cycle Percentage	Indication to the Drivetrain ECM
Less than 5%	Feedback line short to ground.
10%	EFR not enabled, power, and PWM are received - waiting for "EFR Enable" command.
20%	EFR in Standby - Internal boost voltage is high with output command disabled.
30%	Input voltage out of range
40%	Output short circuit - Output shorted high or low
50 %	Normal operation - No faults present.
60%	Output open circuit.
70%	Output current too high
80%	PWM command from Drivetrain ECM out of the normal range (3% to 97%)
90%	Undefined internal EFR fault.
100%	Feedback circuit shorted to another voltage source.

At key start switch ON, the EFR checks for abnormal conditions in the circuits and checks for normal system voltage input. If these conditions are normal, the EFR will set the diagnostic feedback circuit to an approximate 10 percent duty cycle. This duty cycle indicates that the EFR has not detected a problem and is waiting for the enable signal from the Drivetrain ECM. The duty cycle will remain at approximately 10 percent until the ECM sends the enable signal.

Note: Anytime that the Engine is OFF, the key start switch is in the ON position and no abnormal conditions are detected, the EFR feedback circuit PWM duty cycle should be 10 percent - waiting for enable.

At Engine start up, the Drivetrain ECM will determine if the correct drivetrain system conditions are present that will allow EFR operation. When the conditions are correct, the ECM will check the feedback duty cycle. If the EFR feedback signal is 10 percent, the Drivetrain ECM will send an enable signal to the EFR by creating a PWM signal using an ON/OFF driver enable circuit. The duty cycle of this enable signal will be in the range of 5 percent to 95 percent.

The EFR will detect the enable duty cycle and set the diagnostic feedback circuit duty cycle to 50 percent. This signals to the Drivetrain ECM that the EFR is ready for operation.

Once enabled and during normal EFR operation, the PWM duty cycle of the diagnostic feedback circuit will remain at 50 percent. The duty cycle indicates to the Drivetrain ECM that no detected fault conditions are present. If the EFR detects that the enable signal from the ECM is no longer valid or if the EFR detects an abnormal condition in a circuit, the duty cycle of the diagnostic feedback circuit will be changed to one of the listed values in the table.

When the ECM detects the change in the duty cycle, the ECM will disable EFR operation. The ECM will disable the operation of the electric drive train. The ECM will activate a diagnostic code for the involved circuit that will indicate the detected condition.

The diagnostic codes that the Drivetrain ECM can activate for the EFR circuits are:

MID 081, CID 3008 - FMI's 02, 03, 04, 08 - Generator Excitation Field Regulator Diagnostic Feedback Line. - A problem has been detected in the diagnostic feedback circuit or the return circuit.

MID 081, CID 3009 - FMI's 03, 05, 06 - Generator Excitation Field Regulator Current Drive Circuit. - A problem has been detected in the exciter (+) circuit or the exciter (-) circuit that is used to send current to the exciter stator windings.

MID 081, CID 3425 - FMI's 03, 05, 06 - Generator Excitation Field Regulator Enable Line, - The PWM enable signal from the Drivetrain ECM has been interrupted.

MID 081, CID 3460 - FMI 08 - Generator Excitation Field Regulator Command Line. - The PWM current command signal from the Drivetrain ECM that is used to control the EFR current output has been interrupted.

MID 081, CID 3500 - FMI's 03, 04, 08 - Generator Excitation Field Regulator Current Line. - The PWM current feedback signal that is used to inform the Drivetrain ECM of the status of the output current has been interrupted.

MID 081, CID 3501 - FMI's 04, 07 - Generator Excitation Field Regulator. - This code is activated for different conditions depending on the FMI code that is activated. Refer to the troubleshooting procedure in this manual for the code that is active.

Note: A loss of the Drivetrain ECM 5.0 VDC sensor power supply to the EFR will cause the current feedback circuit and the diagnostic feedback circuit to go to a high voltage condition (FMI 03). The ECM will activate a CID 3500, FMI 03 diagnostic code for the current feedback circuit AND a CID 2008, FMI 03 diagnostic code for the diagnostic feedback circuit. If both of these codes are active, always verify that the Drivetrain ECM 5 VDC power supply is present at the harness connector for the EFR.

Note: When a high current condition is detected in the EFR current drive circuits, the Drivetrain ECM will activate an MID 081, CID 3009 - FMI 06 diagnostic code. A possible cause of this condition can be one or more faulty rotating diodes in the Generator rotating diode assembly. Refer to the troubleshooting procedure for this diagnostic code in this manual for more information.

The troubleshooting procedures for these EFR diagnostic codes will provide more details for possible causes of the code that is active.

Generator Operation

Generator internal components

After the Engine is started and the EFR is enabled, the DC current output that is sent from the EFR to the exciter field winding will result in a magnetic field being set up on the stationary exciter stator windings.

When the rotating three phase exciter armature (rotor) windings pass through the magnetic field, three phases of AC voltage are created in the armature windings which are connected to the Rotating Rectifier Assembly.

The full wave bridge rectifier converts the three phases of AC voltage to a DC voltage. The three phases of AC voltage enable the rectifier to convert to a DC voltage that has little ripple.

This DC voltage is converted through the diodes to the positive (+) plate and the negative (-) plate in the rectifier assembly. These plates are connected to the Generator main rotor windings. The converted voltage creates the rotating main rotor magnetic field.

As the rotating main rotor magnetic field pass the three phase connected Generator Stator Windings, AC voltages and currents are induced that result in the Generator three phases of output.

When the Drivetrain ECM determines that more or less Generator output power is required, the ECM will command the EFR to adjust the output current to the exciter stator windings. When the EFR supplies more current to the exciter windings, the exciter stator magnetic fields will strengthen. The result is a higher level of current output from the Generator. Less current to the exciter windings results in less output current being generated.

Generator output connection diagram

The top Generator high voltage enclosure that houses the three phase output cable connections

The three phase output of the Generator is directed to the AC bus bars in the Inverter Cabinet through three high voltage cables. The AC bus bars in the cabinet are connected to two identical traction rectifier assemblies. One traction rectifier is connected in reverse as compared to the other rectifier. The rectifiers convert the three phase AC voltage to the positive (+) and negative (-) sides of the DC Power Bus.

During machine operation, the Generator is cooled by the system cooling airflow. The cooling air is directed into the Generator by duct work that is connected to the drive end cover plate. These ducts are connected to the main cooling air duct that is routed out of the Inverter cabinet and under the Generator.

Generator Temperature Sensors

Generator auxiliary connection enclosure terminal block connections - located on the left-hand side of the Generator

Generator auxiliary connection enclosure terminal strips

Generator Bearing Temperature Sensors

During machine operation, the Drivetrain ECM monitors the operating temperature of two of the generator stator windings. the ECM also monitors the operating temperature of the two generator shaft bearings.

Location Generator Bearing Temperature Sensor on the drive end

Each of the two Generator shaft bearings has a probe type temperature sensor inserted in the Generator housing. The temperature sensors monitor the operating temperature of the bearings.

The drive-end (engine end) bearing sensor is the Generator Bearing 1 Temperature Sensor and the non-drive end bearing sensor is the Generator Bearing 2 Temperature Sensor.

The temperature sensors are base rated 100 ohm (at 0.0° C (32.0° F)) Resistance Temperature Detectors (RTD). The sensor is a three wire sensor. The red wire is the positive circuit. The two white wires are redundant parallel return circuits.

The ECM will use an internal capacitance circuit in order to determine the resistance of the circuit.

The bearing temperature sensors are serviceable. When a bearing temperature sensor has failed, the sensor can be removed from the Generator and replaced.

The expected resistance of a 100 ohm base rated RTD temperature sensor can be calculated for a known winding temperature by using the following calculations:

• The coefficient is .392 ohms per each Celsius degree of temperature
• The formula is: .392 ohms x temperature + 100 ohms = sensor resistance (ohms)
• For a temperature of 60°C, the calculation would be .392 ohms x 60 = 23.52 ohms + 100 ohms = 123.52 ohms.
• For a temperature of -10°C, the calculation would be .392 ohms x -10 = -3.92 ohms + 100 ohms = 96.08 ohms.

The resistance calculation for the temperature sensor resistance will only be useful if the approximate bearing temperature is known. If the resistance of RTD circuits between the signal wire and the return wire is known, the temperature of the bearing can be figured using the following calculation:

• The formula is: sensor circuit resistance (ohms) - 100/.392 = degrees Celsius
• For a circuit resistance 131.5 ohms, the calculation to find temperature would be 131.5ohms -100 = 31.5 ohms divided by .392 = 80.5° C (177° F).

The Drivetrain ECM will activate a level 2 Event if a bearing reaches a temperature of 85° C (185° F) for 10 seconds or a level 3 Event if a bearing reaches a temperature of 95° C (203° F) for 10 seconds. The specific EIDs for the temperature sensor circuits are E0724 for Bearing 1 and E0725 for Bearing 2.

If the Drivetrain ECM detects that there is a problem in a bearing sensor circuit, the ECM will activate a diagnostic code for the involved circuit (CID 3015 for Bearing 1, CID 3016 for Bearing 2).

Generator Stator Winding Temperature Sensors

Each of the three Generator stator windings has two temperature sensors imbedded in the winding.

The sensors are the same type of sensor that is used for the Generator bearings. The temperature sensors are base rated 100 ohm (at 0.0° C (32.0° F)) Resistance Temperature Detectors (RTD). The sensor is a three wire sensor. The red wire is the positive circuit. The two white wires are parallel return circuits. Two return circuits help to eliminate wire resistance effects from the measurements.

Refer to the calculations listed for the bearing sensors in order to calculate the resistance of the winding sensors.

The Drivetrain ECM will use two temperature sensors at any one time to determine the operating temperature of the stator windings. The two temperature sensors are referred to as the Generator Winding 1 Temperature Sensor and the Generator Winding 2 Temperature Sensor. These names are used to differentiate the two separate sensor circuits. The names do not refer to specific temperature sensors.

The stator winding temperature sensors are not serviceable. If a temperature sensor has failed, one of the remaining four spare temperature sensors should be connected as a backup. The backup sensor can be connected at the terminal block in the auxiliary connection enclosure on the left-hand side of the Generator.

If the Drivetrain ECM detects that the temperature of a winding is above the acceptable limits, the ECM will activate a level 2 Event if a winding reaches a temperature of 155° C (311.0° F) for 10 seconds or a level 3 Event if a winding reaches a temperature of 165° C (329.0° F) for 10 seconds. The specific EIDs for the temperature sensor circuits are E0738 for the sensor that is connected to the winding 1 circuit and E0739 for the sensor that is connected to the winding 2 circuit.

If the Drivetrain ECM detects that there is a problem in a winding sensor circuit, the ECM will activate a diagnostic code for the involved circuit (CID 2780 for the winding 1 circuit, CID 2781 for the winding 2 circuit).

See You Soon!!!

MARYGAR

795F AC Off-Highway Truck Electric: Electric Power Generation : Generator Control and Operation 2012-12-01T07:51:00-08:00 Rating: 4.5 Diposkan Oleh: Unknown