BMW 3: Electrical machine electronics (EME)

Electrical machine electronics

The function of the Electrical Machine Electronics (EME) is to activate and regulate the permanently excited synchronous machine in the high-voltage vehicle electrical system. This necessitates the use of a bidirectional DC/AC converter which converts the high-voltage direct current voltage of the high-voltage battery unit into a three-phase AC voltage for the electrical machine. When the electrical machine is operating in generator mode, the high-voltage battery unit is recharged via the inverter.

The EME also incorporates the DC/DC converter which is responsible for the power supply to the low- voltage electrical system. The EME is connected to the PT-CAN, K-CAN5 and FlexRay.

Battery management electronics (SME)

The SME control unit is integrated in the high-voltage battery unit. To maximize the service life of the high-voltage battery unit, the battery management electronics control unit ensures that it is operated in a precisely defined range (state of charge and temperature). Other tasks of the battery management electronics control unit include start-up and shut-down of the high-voltage system, safety functions (e.g. high-voltage interlock loop) and determination of the available power of the high-voltage battery unit. The battery management electronics communicates with other control units via the K-CAN5.

Cell Supervision Circuit (CSC)

Certain conditions must be observed for fault-free operation of the lithium-ion cells in the G20 PHEV: The cell voltage and the cell temperature cannot exceed or drop below certain values as otherwise the battery cells may suffer long-term damage. For this reason, each high-voltage battery unit has several Cell Supervision Circuits (CSC).

One main cell supervision circuit and 5 series-connected secondary cell supervision circuits are installed. Only the main cell supervision circuit communicates via the local CAN1 with the SME. The secondary cell supervision circuits communicate with the respective predecessor and successor control unit in the CSC wiring harness.

Electric A/C compressor (EKK)

An electrically operated air conditioning compressor is used in the G20 PHEV. To be able to provide the necessary power, the electric air conditioning compressor EKK is operated at high voltage. The EKK enables air conditioning operation in all driving situations. In addition to cooling the vehicle interior, the refrigerant circuit cools the high-voltage battery unit. The EKK control unit is located in the housing of the air conditioning compressor; it is connected to the integrated automatic heating/air conditioning system via the LIN bus.

Electrical Heating (EH)

Due to its hybrid concept, the combustion engine of the G20 PHEV generates significantly less heat loss in many driving situations and is not able to heat the coolant circuit to the necessary temperature.

This is why the G20 PHEV has electrical heating. In principle, this functions similar to an instantaneous water heater. The electrical heating control unit is located in the housing of the electrical heating and is connected via the LIN bus to the integrated automatic heating / air-conditioning (IHKA).

Intelligent Battery Sensor 2 (IBS2)

The intelligent battery sensor 2 monitors the current, voltage and the pole temperature of the auxiliary battery. The results are forwarded via LIN bus to the EME.

Hybrid pressure refuelling electronic control unit (TFE)

The hybrid pressure refuelling electronic control unit uses a pressure temperature sensor in the fuel tank to monitor the current operating condition and then controls the pressure reduction by opening the valves in the tank ventilation path. After completing pressure reduction, the controller drive for the fuel filler flap lock is activated and the fuel filler flap and fuel filler cap can be opened manually.

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