BMW 3: Power electronics for activation of the electrical machine
The power electronics for the activation of the electrical machine are mainly made up of the bidirectional DC/AC converter. It is a pulse converter with a 2-pin DC voltage connection and a 3-phase AC voltage connection. This DC/AC converter can work as an inverter and conduct electrical energy from the high-voltage battery unit to the electrical machine when it is to work as a motor.
However, the DC/AC converter can also work as a rectifier and transfers electrical energy from the electrical machine to the high-voltage battery unit. This operating mode occurs during brake energy regeneration (energy recovery) in which the electrical machine works as an alternator and "generates" electrical energy.
Operating modes of the bidirectional DC/AC converter
- Schematic diagram
- Schematic diagram with components
- High-voltage battery unit
- Operating mode as inverter, electrical machine works as an engine
- Operating mode as rectifier, electrical machine works as an alternator
- DC/AC converter
- Current sensors
- Electric motor
The operating mode of the DC/AC converter is defined by the EME control unit. The EME control unit also receives the setpoint values (essential input variables) from the DME control unit for which torque (amount and sign) the electrical machine should supply. From this setpoint value and the current operating condition of the electrical machine (engine speed and torque) the EME control unit determines the operating mode of the DC/AC converter, as well as the amplitude and frequency of the phase voltages for the electrical machine. According to these specifications, the power semiconductors of the DC/AC converter are activated in sync.
In addition to the DC/AC converter, the power electronics also contains current sensors in all 3 phases on the AC voltage side of the DC/AC converter. Using the signals from the current sensors, the EME control unit monitors the electrical power which is used in the power electronics and electrical machine and what torque the electrical machine generates. The control loop of the Electrical Machine Electronics is closed by the signals of the current sensors and the rotor position sensor in the electrical machine.
The performance data of the Electrical Machine Electronics and the electrical machine were coordinated in development. The Electrical Machine Electronics can deliver a continuous electrical power of 55 kW and a temporary maximum power of 83 kW. In order to avoid overloading the power electronics, there is also another temperature sensor at the DC/AC converter. If an excess temperature of the power semiconductor is identified using this signal, the EME control unit reduces the power delivered to the electrical machine in order to protect the power electronics.
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High-voltage power management
The power management for the high-voltage vehicle electrical system includes
two subfunctions: one
for driving and one for charging mode.
In driving mode, the energy flows from the high-voltage batt
Voltage supply for other high-voltage consumers
The Electrical Machine Electronics supplies voltage not only to the
electrical machine. The
convenience charging electronics are directly connected with the Electrical
Machine Electronics and
ensure
Cooling
The Electrical Machine Electronics and convenience charging electronics (KLE)
are cooled by the low-
temperature coolant circuit.
G20 PHEV, low-temperature coolant circuit (schematic diagram)
Radi
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Seats
Safety information
Warning
Seat adjustments while driving can lead to unexpected
movements of the seat. Vehicle control
could be lost. There is a risk of accident.
Only adjust the seat on the driver's side when
the vehicle is stationary.
Warning
With a backrest inclined too far to the rear, the
e
Convenience charging electronics (KLE)
Convenience charging electronics
The convenience charging electronics enable communication between the vehicle
and charging
station of the AC voltage supply in order to charge the high-voltage battery
unit. The convenience
charging electronics convert the AC voltage into high-voltage direct curre
