High-voltage interlock
48
Electrical system
Introduction of smart fortwo electric drive (3rd Generation) • Model Series 451
The interlock loop is used to protect people from
faults in the high-voltage on-board electrical
system. The interlock loop detects an open
connector circuit in the high-voltage on-board
electrical system.
The interlock signal is generated in the battery
management system control unit and passes in a
loop via the following components:
• High-voltage battery
• On-board charger
• High-voltage PTC heater
• Electric refrigerant compressor
• Power electronics control unit
• High-voltage adapter plate fuse box
• Electric drive motor
• Service Disconnect
• Interior/engine connector
If the signal loop is interrupted, e.g. by discon-
necting a high-voltage or 12 V connector, this
causes the contactors in the high-voltage battery
module to open and the high-voltage on-board
electrical system to shut down. Since capacitors
are also present in the high-voltage components,
the high-voltage on-board electrical system is
not immediately rendered voltage-free once the
contactor is opened. For this reason, an active
discharge function is incorporated in the high-
voltage components. This discharges the high-
voltage on-board electrical system to voltages
below 60 V in less than 5 s.
If the interlock signal is interrupted during
driving operation, the high-voltage on-board
electrical system is only shut off the next time the
vehicle is stopped when the selector lever is
moved to position "P" with the vehicle at a stand-
still or the vehicle key is turned to position "Off".
