Electric Drive, Function - GF08.00-P-0001KJE
ENGINE 780 in MODEL 453.091/391/491
Overview of the high-voltage components
Function requirements, general
- Terminal 15
Function description for electric drive, general
The electric drive consists of the electric vehicle drive motor (M5), the transmission and the high-voltage control unit box (N83). The DC/DC converter control units (N83/1), charging process monitoring (N83/2) with 7 kW charger or charger for high-voltage battery (22 kW charger) (N83/10), power electronics (N129/1) and high voltage distribution are integrated in the high-voltage control unit box. The traction management takes place through the EDCU (N127) (master control unit). This directly reads in the signal of the accelerator pedal sensor (B37). The energy management takes place through the EDCU. Other relevant data for the vehicle control (for example engaged gear range) are read in via the electric drive CAN (CAN EL).
The EDCU uses these data to determine the power requirements upon the electric drive and requests this via the electric drive CAN (CAN EL) from the power electronics control unit. The power electronics control unit actuates the electric vehicle drive motor with 3-phase AC voltage over the integral rectifier and monitors the electric vehicle concerning temperature and the generated drive torque. The electric vehicle drive motor transfers the drive torque over a fixed stepped-down transmission (i = 9.34:1) to the drive shafts and the rear wheels.
In order to protect the electric drive from overheating, the electric vehicle drive motor is air cooled by the electric vehicle drive motor fan (M46).
The high-voltage control unit box, the high voltage charger control unit (N83/5) and the high-voltage battery (G5) are cooled over a coolant circuit.
Information about the energy flow and the charge level of the high-voltage battery is received by the driver over the IC (A1) and the additional instruments (A15).
The function description for the electric drive is subdivided as follows:
- Direction of travel
- Transmission
- Driving mode
- Deceleration mode
- Vehicle network support
- High voltage rapid discharging in the case of a crash
- Heat management
- Power limit
Direction of travel
The direction of travel is prescribed by the driver over selection of the gear range over the electronic selector lever module control unit (N15/5).
The electronic selector lever module control unit detects the shift lever positions over integral Hall sensors, evaluates these and transmits the respective signals via the electric drive CAN (CAN EL) to the EDCU.
The EDCU requests the respective direction of travel according to the selector lever position from the power electronics control unit. The power electronics control unit actuates the electrical machine by means of a 3-phase AC voltage via the integral rectifier.
Reverse travel for the selector lever position "R" is realized in this case through reversing the direction of rotation of the electric vehicle drive motor.
Transmission
The transmission is designed as a fixed ratio single stage transmission with integral bevel gear differential.
Matching of the torque of the drive wheels takes place in the bevel gear differential.
Engaging the park pawl takes place manually over a cable.
Driving mode
In the drive mode the electrical power from the high-voltage battery system is converted to mechanical drive energy. To do this the high voltage direct voltage from the high-voltage battery is led over the electrical line and the high-voltage control unit box to the power electronics control unit. In the power electronics control unit, the high voltage direct voltage is converted in the integral rectifier into a 3-phase AC voltage and fed to the electric vehicle drive motor. The power electronics control unit reads and permanently evaluates the position, rotational speed and temperature of the electric vehicle drive motor over the electrical machine rotor position sensor (L20). The power electronics control unit also monitors the status of the rectifier. The status of the electric vehicle drive motor and the rectifier is reported by the power electronics control unit via the electric drive-CAN to the EDCU. The EDCU creates forecasts over the performance capability of the electric drive from this data.
The EDCU then requests the power requirements on the basis of these forecasts to the power electronics control unit via the electric drive CAN. The power electronics control unit regulates the frequency and amplitude of the alternating stress and therefore directly the generated drive torque dependent on the performance specifications over the rectifier.
Sound output during vehicle operation: In the vehicle speed range from v = 1 to 30 km/h, an engine noise is output by the electric vehicle sound generator via an integrated speaker. At speeds greater than 30 km/h, the sound generator is deactivated, as the vehicle's rolling and wind noises are loud enough. The powertrain control unit transmits the following signals via the electric vehicle CAN to the electric vehicle sound generator to implement the function:
- current selector lever position
- Vehicle speed
- Pedal value
Dependent on the speed (read in by the left front axle rpm sensor (L6/1), right front axle rpm sensor (L6/2), left rear axle rpm sensor (L6/3) and right rear axle rpm sensor (L6/4)) and accelerator pedal position (read in by the accelerator pedal sensor (B37)), a noise similar to the engine noise of an internal combustion engine vehicle is issued over the electric vehicle SOGE (H4/16) between 0 to 30 km/h. For a speed greater than 30 km/h the SOGE is deactivated since the rolling and wind noises of the vehicle are loud enough.
Deceleration mode
If the brake pedal and accelerator pedal is not actuated for a rolling vehicle, the kinetic energy can be taken up over the electric vehicle drive motor and converted into electrical energy (regenerative braking) according to the driving situation. Conversion of the electrical energy into a mechanical braking torque simulates the engine drag torque of a vehicle with an internal combustion engine.
The energy recovered in decel mode serves to supply the high voltage consumers and to charge the high-voltage batteries. To do this the electrical energy generated by the electric vehicle drive motor is fed back over the rectifier into the high voltage on-board electrical system.
The distance warning function controller unit with radar sensor (A89) with CODE 252 (Collision warning system (FCW) registers the distance and the difference in speed from the preceding vehicle, and transmits these data via the front end CAN (CAN-G) to the distance warning function gateway (N93/2), via the interior CAN to the center SAM control unit (N10/10) and via the electric CAN to the electric drive control unit.
The distance warning function controller unit with active intervention by the brake system (A90) with CODE 258 (COLLISION PREVENTION ASSIST) registers the distance and the difference in speed from the preceding vehicle, and transmits these data via the front end CAN (CAN-G) to the center SAM control unit (N10/10) and via the electric CAN to the electric drive control unit.
The engine drag torque to be set is dependent on the driving situation is adjusted infinitely in the EDCU.
After the ignition is switched on, gear range D is always set. The vehicle is always in the position D (moderate regenerative braking).
Automatic adaptation of the regenerative braking on inclines
In order to limit acceleration when traveling downhill the regenerative braking torque is increased appropriately in order to acceleration when traveling downhill to a comfortable amount.
The incline and the desired braking torque (read in from the brake lights switch (S9/1)) is detected by the EDCU. The EDCU calculates the corresponding specified deceleration and sends the request for regenerative braking torque via electric drive system CAN to the power electronics control unit. The power electronics control unit actuates the electric vehicle drive motor respectively regeneratively.
Vehicle network support
All implemented control units are supplied via the 14 V on-board electrical system battery (G1). The on-board electrical system support ensures that it is charged at all times. If the desired charge level of the battery is not reached or the outside temperature during the driving goes below a threshold value, it will be charged over the DC/DC converter control unit (N83/1). In doing so the comfort functions in the on-board electrical system are switched off for the duration of the charging.
The DC/DC converter control unit converts the high voltage to the voltage level of the 14 V on-board electrical system to supply the 14 V consumers and to charge the on-board electrical system battery. To do this the DC/DC converter control unit receives a voltage specification for the 14 V on-board electrical system from the center SAM control unit (N10/10) via CAN.
- Extra charging
Extra charging is an on-board electrical system strategy to maintain the operability of the 14 V on-board electrical system battery during long idle times in the warehouse and at the customer. There are two modes.
- Delivery mode
This mode is active for 90 days or a mileage of 30 km, and enables automatic extra charging. If the vehicle is "woken" during this time, the high-voltage battery charges the 14 V battery every 30 days for 6 hours. The service cover must be closed to do this.
- Customer mode
In this case the vehicle must be connected to a charging station and the threshold value of the battery is undershot. The high-voltage battery is charged first.
High voltage rapid discharging in the case of a crash
If a crash occurs during the charging process or a rollover while driving, the crash sensor, high-voltage control unit (N2/1) switches the high voltage on-board electrical system off. In the event of a crash, the high-voltage on-board electrical system is discharged to a voltage of < 60 V by the electric drive within 5 seconds. The energy is converted to heat in the stator coil of the electric vehicle drive motor.
Cooling circuit without battery cooling system, shown as an example with 7 kW charger
Cooling circuit with battery cooling system (code V03), shown as an example with 22 kW charger (code 908)
Heat management
There is a by-product produced during conversion of electrical energy into kinetic energy and inversion of the various voltages (12 V/high voltage/3-phase alternating stress): waste heat. The electric drive is fitted with a cooling circuit to dissipate this waste heat. This cools the high-voltage battery, the high-voltage control unit box and the charger control unit for the high-voltage battery (7 kW charger) and delivers up the excess thermal energy over the cooler to the ambient air. If the air flow is not sufficient to do this the fan motor (M4/7) is also actuated by the EDCU (N127).
To circulate the coolant in the cooling circuit, the EDCU actuates and monitors the coolant pumps for the high-voltage control unit box and the high-voltage battery according to the temperature of the power electronics, the charger control unit (evaluated internally) and the temperature of the cooling circuit. The temperature sensors for the coolant circuit are located in the high-voltage control unit box and in the high-voltage battery.
- Frequent acceleration phases occurred shortly one after the other
- Power electronics overheating (converter temperature > 100°C)
- Fault recognized on the coolant pump
- Defective temperature sensors recognized
- Coolant level too low
- Defective high-voltage battery recognized
- Output limitation due to a high-voltage battery temperature which is too low (< 0°C) or too high (> 50°C)
- Output limitation due to a high-voltage battery state of charge which is too low
- Output limitation due to excessively high current consumption from the high-voltage battery
The available output of the electric drive is shown over the additional instruments (A15).
For vehicles with code (V03) Battery cooling system the refrigerant circuit is brought together over an additional heat exchanger (chiller) near the high-voltage battery with the cooling circuit. Two expansion valves extend the refrigerant circuit. The electrical expansion valve (FIR) (Y19/1) can be switched off electrically. The electrical expansion valve (battery) (Y19/3) is located on the chiller.
The electric vehicle drive motor is not integrated into the coolant circuit but is cooled instead over the electric vehicle drive motor fan (M46). Detailed information about the fan motor can be found in the separate "Fan motor component description" function description.
Detailed information about the heater circuit is contained in the separate "Heater circuit function" description.
Detailed information about the refrigerant circuit is contained in the separate "Refrigerant circuit function" description.
Power limit
The electric drive limits the actual torque or reduces the maximum possible output and speed under the following conditions:
- Overheating of the electric vehicle drive motor (winding temperature > 180°C)
| Electrical function schematic for electric drive | PE08.00-P-2050-97BBE | ||
| Overview of system components for an electrical vehicle | GF08.00-P-9999KJE |