BMW I01 Product Information page 147

I01￿High-voltage￿Components
8.￿Electric￿Heating
Index
15
16
17
18
The￿current￿through￿the￿individual￿strands￿is￿measured￿and￿controlled￿by￿the￿electric￿heating￿control
unit.￿A￿current￿of￿maximum￿20￿A￿flows￿in￿a￿voltage￿range￿of￿250 V￿to￿400 V.￿The￿power￿is￿reduced
above￿and￿below￿this￿voltage￿range.￿At￿increased￿power￿consumption￿the￿energy￿supply￿by￿the
hardware￿switching￿is￿interrupted.￿This￿switching￿is￿designed￿so￿that￿even￿in￿the￿event￿of￿a￿fault￿in￿the
control￿unit￿a￿power￿cut￿is￿effected￿safely.
The￿temperature￿of￿the￿coolant￿is￿measured￿using￿a￿sensor￿at￿the￿output￿of￿the￿electric￿heating.
Inside￿the￿electric￿heating￿a￿galvanic￿separation￿was￿installed￿between￿the￿high-voltage￿circuit￿and￿the
low-voltage￿circuit.
The￿connections￿for￿local￿interconnect￿network￿bus￿and￿voltage￿supply￿(terminal￿30B)￿are￿located￿at
the￿low-voltage￿connector.
A￿bridge￿is￿integrated￿in￿the￿high-voltage￿connector￿beside￿the￿contacts￿for￿the￿high￿voltage.￿The
contacts￿of￿the￿bridge￿in￿the￿high-voltage￿connector￿are￿designed￿as￿leading￿contacts.￿This￿means
when￿removing￿the￿high-voltage￿connector￿the￿contacts￿of￿the￿high-voltage￿bridge￿are￿separated￿first.
As￿a￿result,￿the￿voltage￿supply￿of￿the￿control￿unit￿(EH)￿is￿interrupted.￿This￿also￿means￿the￿high-voltage
supply￿is￿interrupted￿before￿the￿high-voltage￿connector￿is￿pulled￿out￿fully.￿No￿electric￿arc￿thus￿arises
on￿the￿high-voltage￿contacts.￿The￿high-voltage￿contacts￿are￿protected￿from￿contact.￿The￿high-voltage
connector￿of￿the￿electric￿heating￿is￿not￿part￿of￿the￿circuit￿of￿the￿high-voltage￿interlock￿loop.
8.3.￿Control￿system
Six￿heating￿stages￿can￿be￿set￿through￿separate￿or￿combined￿activation￿of￿the￿individual￿heater￿coils.
The￿request￿for￿switching￿on￿the￿heating￿comes￿from￿the￿IHKA￿control￿unit￿via￿local￿interconnect
network￿bus.
Heater￿coil
1
2
3
1￿+￿3
2￿+￿3
1￿+￿2￿+￿3
When￿the￿maximum￿temperature￿is￿reached￿or￿if￿the￿maximum￿permissible￿current￿level￿is￿exceeded,
the￿heater￿output￿is￿automatically￿restricted￿by￿the￿electric￿heating￿control￿unit.
The￿electric￿heating￿is￿switched￿off￿in￿the￿event￿of￿system￿faults.
The￿electric￿heating￿is￿maintenance-free.
Explanation
Electronic￿switch￿(Power￿MOSFET)￿for￿heater￿coil￿3
Heater￿coil￿1
Heater￿coil￿2
Heater￿coil￿3
Heating￿stage
1
2
3
4
5
6
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