Electrical machine with rotor position sensor

The electrical machine, including separating clutch, is installed between the combustion engine and the automatic gearbox. The electrical machine consists of stator (inside) and rotor (outside). The rotor replaces the flywheel of the combustion engine. The electrical machine is designed as a permanently excited electric motor (synchronous) with a maximum output of 39 kW. The electrical machine has the following functions:

• Electrical driving
• Support for the combustion engine (boost)
• Electrical brake (recuperation = energy recuperation)
• Alternator

For boosting (electrical acceleration), up to 210 Nm additional electromotive torque can be provided.

Fig 1: Identifying Coolant Lines Connection

Courtesy of BMW OF NORTH AMERICA, INC.

The rotor position sensor records the exact position of the rotor or the electrical machine. The rotor position sensor is constructed in the same way as a synchronous motor. The specially shaped rotor is connected to the rotor of the electrical machine. The stator is connected to the stator of the electrical machine. The voltages induced by turning the rotor in the coils of the stator are evaluated by the Electrical Machine Electronics (EME) and the rotor position angle is calculated.

The rotor position angle is imperative for exact, field-oriented control of the electrical machine in order to create the voltages at the coils of the stator that match the position of the rotor.

The coils of the electrical machine must not exceed a certain temperature during operation. This is why a representative temperature in one of the coils is measured using a temperature sensor (NTC).

The Electrical Machine Electronics (EME) evaluate the signals from the temperature sensor. The EME reduces the power output of the electrical machine if the temperature of the coils approaches maximum permitted value.

Fig 2: Identifying Temperature Sensor And Rotor Position Sensor Stator

Courtesy of BMW OF NORTH AMERICA, INC.