Motor description
Electric drive system
65
Introduction of smart fortwo electric drive (3rd Generation) • Model Series 451
The smart fortwo electric drive is driven by a
permanently energized 3-phase AC motor with
35 kW continuous output and 55 kW peak output.
An inverter in the power electronics control unit
converts the direct voltage of the high-voltage
battery into 3-phase alternating voltage for
operating the electric motor. The rpm of the
motor is determined by the frequency and the
torque via the PWM duty cycle of the AC voltage.
The power electronics control unit is connected
directly to the high-voltage adapter plate fuse
box. The electric motor is connected to the high-
voltage adapter plate fuse box via 3 high-voltage
lines. The operating parameters such as rotor
position, rpm and motor temperature are trans-
mitted to the power electronics control unit over
another connector.
The direction of rotation of the electric drive
motor is reversed for reverse travel.
In deceleration mode, the electric drive motor
operates as a generator (regenerative braking).
In this case, the voltage generated by the motor is
fed to the high-voltage on-board electrical
system via the power electronics control unit.
The efficiency of the power electronics and elec-
tric motor depends on the operating temperature.
The power electronics control unit and electric
drive motor are cooled by a coolant circuit. At a
coolant temperature between 80 °C and 90 °C,
measured by the power electronics control unit,
the output is reduced by the power electronics
control unit down to 0 kW on a linear basis.
P08.10-2052-00
Electric drive system
1 Transmission
F34/6 High-voltage adapter plate fuse box
M5 Electric drive motor
N129/1 Power electronics control unit
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