BMW I01 Product Information page 68

I01￿High-voltage￿Components
4.￿Electrical￿Machine￿Electronics
• Standby￿(also￿in￿the￿event￿of￿a￿component￿fault￿or￿short￿circuit,￿power￿electronics￿off)
• Buck￿mode￿(Energy￿flow￿to￿the￿low-voltage￿side.￿Converter￿controls￿voltage￿on￿low-voltage
side)
• Discharging￿the￿high-voltage￿link￿capacitor￿(interlock￿fault,￿accident,￿request￿from￿master).
The￿DC/DC￿converter￿is￿in￿"Standby"￿mode￿when￿the￿electrical￿machine￿electronics￿is￿not￿in
operation.￿This￿is￿the￿case￿when￿the￿EME￿control￿unit￿is￿not￿supplied￿with￿voltage￿due,￿for￿example,
to￿a￿terminal￿status.￿But￿also￿if￿there￿is￿a￿fault￿the￿EME￿control￿unit￿prompts￿the￿DC/DC￿converter￿to
assume￿"Standby"￿mode.￿In￿this￿operating￿mode￿there￿is￿no￿energy￿transfer￿between￿the￿two￿vehicle
electrical￿systems￿and￿they￿remain￿galvanically￿separated.
Buck￿mode￿is￿the￿normal￿operating￿mode￿when￿the￿high-voltage￿system￿is￿active.￿The￿DC/DC
converter￿transfers￿electrical￿energy￿from￿the￿high-voltage￿electrical￿system￿to￿the￿12 V￿vehicle
electrical￿system￿and￿assumes￿the￿function￿of￿the￿alternator￿in￿a￿conventional￿vehicle.￿The￿DC/DC
converter￿must￿reduce￿the￿varying￿voltage￿from￿the￿high-voltage￿electrical￿system￿to￿the￿voltage￿in￿the
low-voltage￿vehicle￿electrical￿system.￿The￿voltage￿in￿the￿high-voltage￿electrical￿system￿is￿dependent,
for￿example,￿on￿the￿state￿of￿charge￿of￿the￿high-voltage￿battery￿(about￿260 V￿to￿about￿390 V).￿The
voltage￿in￿the￿low-voltage￿vehicle￿electrical￿system￿controls￿the￿DC/DC￿converter￿so￿that￿the￿12 V
battery￿is￿optimally￿charged￿and￿sets￿a￿voltage￿of￿about￿14 V￿depending￿on￿the￿state￿of￿charge￿and￿the
temperature￿of￿the￿battery.￿The￿EME￿control￿unit￿communicates￿with￿the￿EDME￿control￿unit,￿in￿which
the￿12 V￿power￿management￿functions￿are￿performed.￿The￿result￿is￿the￿setpoint￿value￿specification￿for
the￿voltage,￿which￿the￿DC/DC￿converter￿should￿adjust￿in￿the￿low-voltage￿vehicle￿electrical￿system.￿The
continuous￿output￿power￿of￿the￿DC/DC￿converter￿is￿2500 W.
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