BMW I01 Product Information page 181

I01￿High-voltage￿Components
12.￿Technical￿Safety￿Precautions
2 The￿systems￿at￿the￿high-voltage￿electrical￿system￿(EME,￿REME,￿KLE,￿EKK,￿EH)￿reduce￿the
currents￿in￿the￿high-voltage￿electrical￿system￿to￿zero
3 Opening￿the￿switch￿contactors￿in￿the￿high-voltage￿battery￿unit￿(controlled￿by￿SME)
4 Discharging￿the￿high-voltage￿circuit,￿i.e.￿active￿discharging￿of￿the￿link￿capacitors￿(EME,￿REME￿and
KLE),￿short-circuit￿of￿the￿coils￿of￿the￿electrical￿machine￿(EME￿and￿REME),￿short-circuit￿of￿the￿coils
of￿the￿EKK
5 Checking￿the￿high-voltage￿system,￿e.g.￿as￿to￿whether￿the￿contacts￿of￿the￿electromechanical
switch￿contactors￿were￿correctly￿opened.
Both￿the￿after-running￿period￿after￿switching￿off￿terminal￿15￿and￿the￿shutdown￿itself￿can￿last￿a￿few
minutes.￿The￿automatic￿monitoring￿functions￿are￿a￿reason￿for￿this,￿for￿example.￿The￿regular￿shutdown
is￿interrupted￿if￿in￿the￿meantime￿either￿a￿request￿for￿a￿renewed￿start-up￿is￿made￿or￿a￿condition￿has
arisen￿to￿request￿a￿quick￿shutdown.
Quick￿shutdown
The￿overriding￿aim￿here￿is￿to￿shut￿down￿the￿high-voltage￿system￿as￿quickly￿as￿possible.￿This￿quick
shutdown￿is￿then￿always￿carried￿out￿if￿for￿safety￿reasons￿the￿voltage￿in￿the￿high-voltage￿system￿has￿to
be￿reduced￿to￿a￿safe￿value￿as￿quickly￿as￿possible.￿The￿following￿list￿describes￿the￿triggering￿conditions
and￿the￿functional￿chain￿leading￿to￿the￿quick￿shutdown.
Accident:
•
ACSM￿identifies￿an￿accident.￿Depending￿on￿the￿severity￿of￿the￿accident￿the￿shutdown￿of￿the
high-voltage￿system￿is￿requested￿via￿bus￿signals.￿The￿SME￿triggers￿the￿separation￿of￿the
switch￿contactors￿in￿the￿high-voltage￿battery.￿In￿the￿case￿where￿communication￿via￿a￿data￿bus
is￿faulty￿or￿not￿possible,￿the￿switch-off￿of￿the￿switch￿contactors￿is￿forced￿(hard￿opening).￿The
switch￿contactors￿are￿supplied￿with￿voltage￿by￿terminal￿30C.￿Through￿the￿separation￿of￿the
safety￿battery￿terminal￿from￿the￿positive￿terminal￿of￿the￿12 V￿battery,￿the￿voltage￿supply￿of￿the
switch￿contactors￿is￿also￿interrupted￿and￿their￿contacts￿open￿automatically.
The￿EME￿and￿the￿REME￿also￿receive￿bus￿signals￿for￿switching￿off￿the￿high-voltage￿system.
Both￿control￿units￿immediately￿trigger￿the￿active￿short￿circuit￿of￿the￿electrical￿machines￿(short-
circuit￿of￿the￿coils￿of￿the￿corresponding￿electrical￿machine￿via￿the￿power￿semiconductor￿of￿the
AC/DC￿converter)￿and￿the￿active￿link￿capacitors￿are￿discharged.￿If￿communication￿via￿the￿data
bus￿is￿not￿possible,￿the￿shutdown￿request￿is￿sent￿via￿the￿separate￿lines￿between￿ASCM￿and
EME,￿as￿well￿as￿between￿ACSM￿and￿REME.
Overload￿current￿monitoring:
•
With￿help￿of￿current￿sensors￿in￿the￿high-voltage￿battery￿unit￿the￿current￿level￿in￿the￿high-
voltage￿electrical￿system￿is￿monitored.￿If￿too￿high￿a￿current￿level￿is￿identified,￿the￿SME￿control
unit￿causes￿a￿hard￿opening￿of￿the￿electromechanical￿switch￿contactors.￿Considerable￿wear
occurs￿to￿the￿contacts￿of￿the￿switch￿contactors￿as￿a￿result￿of￿this￿opening￿under￿a￿high
current,￿which￿must￿be￿accepted￿to￿protect￿the￿other￿components￿from￿damage.
Protection￿in￿the￿event￿of￿a￿short￿circuit:
•
In￿the￿high-voltage￿battery￿unit￿there￿is￿an￿overload￿current￿fuse￿which￿interrupts￿the￿high-
voltage￿circuit￿in￿the￿event￿of￿a￿short￿circuit.
Critical￿cell￿state:
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