ENGINE | 780.993 in MODEL 451.390/392/490/492 |
Interlock circuit
The interlock circuit is used as protection to protect people against inadvertent contact with high-voltage batteries.
A 12 V/88Hz interlock signal is looped here through all high voltage system components that are to be dismantled or opened.
To do this there is a contact bridge in each removable high voltage plug connection which interrupt the interlock circuit during removal of the high voltage plug connection. The interlock circuit is also led switched in a series over the 12 V control units plug connection of the high-voltage components.
P08.20-2037-08
N129/1 Power electronics control unit
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Location
The power electronics control unit is located in the engine compartment over the electric motor drive (M5).
Body
The power electronics control unit is screwed on with the high voltage adapter plate fuse box (F34/6). The power electronics control unit contains a voltage converter and a DC/DC converter.
Task
The power electronics control unit has the following tasks:
Delivery of an AC voltage for the electric motor drive
Transformation between the high-voltage on-board network and the 12V on-board electrical system
Reading in of sensors and signals
Evaluation of input factors
Actuation of components
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Delivery of an AC voltage for the electric motor drive
In order to drive forward the electric motor drive, the voltage converter integrated in the power electronics control unit generates an AC voltage out of the high voltage direct voltage from the high-voltage battery (G5). If the electric motor drive is driven as an alternator (regenerative braking), the voltage converter generates a high-voltage direct voltage again out of the induced AC voltage.
Transformation between the high-voltage on-board network and the 12V on-board electrical system
The DC/DC converter integrated in the power electronics control unit generates a low voltage direct voltage out of the high voltage direct voltage or vice versa.
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There are two different modes in which the DC/DC converter can be operated as required:
- in "Buck" mode the 12 V on-board electrical system is charged from the high-voltage on-board electrical system over the DC/DC converter so an alternator like the one installed in vehicles with an internal combustion engine is simulated.
– in "state by" mode the 12 V on-board electrical system is charged with a maximum
200 W, the communication must however be achieved over the electric vehicle CAN (CAN EV) and with the respective sensors.
Reading in of sensors and signals
The input factors are read in via the following connections:
Direct line
Electric vehicle CAN
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Direct line
The high voltage interlock signal and the signal from the rotor position sensor (L20) are read in over direct lines.
Electric vehicle CAN
The signals are read in by the power electronics control unit via the electric vehicle CAN. The functions that use these signals are described in the individual function descriptions (see block diagram or function schematic).
Evaluation of input factors
The input factors that have been read in are evaluated by the integrated microprocessor and the relevant components are then actuated.
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Actuation of components
The actuation of the components takes place via the following connections:
Direct line
Electric vehicle CAN
Direct line
The following components are actuated via direct lines:
- electric motor drive
- integral DC/DC converter
- powertrain control unit (N127) (start enable)
Electric vehicle CAN
The signals are transmitted by the power electronics control unit via the electric vehicle CAN.
The functions that use these signals are described in the individual function descriptions (see block diagram or function schematic).