Electric machine, basic function

Overview

This document contains information on:

 General

 Function

General

The electric machine converts the electrical energy in engine mode into mechanical energy, and thus provides a drive torque. In generator mode, the electric machine converts mechanical energy into electrical energy (regenerative braking). A vehicle can contain one or two electric machines.

Function

The following applies for vehicles with code ME01 (electric engine):

The electric machine is an asynchronous motor with a cage rotor. The rotor is connected to the output shaft via a permanently transmitted transmission without a mechanical connecting point. The electrical connection is made via the power electronics control unit.

The changeover between the operating modes engine/alternator operation is controlled by the power electronics control unit. To do this, the three phase currents of the electric machine are regulated depending on the operating mode and the rotor position. These phase currents generate a magnetic rotary field which generates a mechanical torque together with the rotor field. In engine mode, this leads to a torque that acts directly on the drive and thus powers the vehicle. In generator mode, the electric machine generates a braking torque.

For vehicles with code ME05 (HYBRID DRIVE 80KW-VARIANT (INCLUDING PLUGIN)), the following applies:

The electric machine is installed as a permanent magnet energized three-phase synchronous machine in the automatic transmission in the transmission bell housing. The rotor of the electric machine is positively connected over the rotor carrier to the engine separator clutch. The electrical connection is made via the power electronics control unit.

For vehicles with code ME08 (Hybrid drive 75-84 KW VARIANT (INCLUDING PLUGIN)) and front wheel drive, the following applies:

The electric machine is designed as a permanently magnet-energized three-phase current synchronous machine. It is installed into the coupling unit together with the engine separator clutch and dual clutch. The design of the electric machine as a wet runner allows for optimum dissipation of rotor and stator heat loss. The electrical connection is made via the power electronics control unit.

The following applies for hybrid vehicles:

The changeover between the operating modes engine/alternator operation is controlled by the power electronics control unit. To do this, the three phase currents of the electric machine are regulated depending on the operating mode and the rotor position. These phase currents generate a magnetic rotary field which generates a mechanical torque together with the rotor field. In engine mode, this leads to a torque, which, depending on the actuation of the engine separator clutch, either acts directly on the drive thus propelling the vehicle or tow starts the combustion engine. In generator mode, the electric machine generates a braking torque, which, depending on the actuation of the engine separator clutch, either decelerates the vehicle or puts a load on the combustion engine.