Electric Machine, Basic Function - GF08.10-P-2000A
Electric vehicles and hybrid vehicles
Example illustration: hybrid vehicle drive components
Example illustration: electric machine with gearing
Overview
This document contains information on:
- General
- Function
- Asynchronous motors
- Permanently excited synchronous motors
- Electric vehicles
- Hybrid vehicles
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 to electrical energy (recuperation).
Function
The electric machine draws the energy required during engine operation via the high-voltage on-board electrical system from a high-voltage battery. The power electronics control unit with integrated power inverter converts the direct voltage from the high-voltage battery to a three-phase alternating voltage to supply the electric machine.
The electric machine can be operated as a motor for the drive or as an alternator for recuperation. The rotational speed of the electric machine is recorded by sensors on the electric machine.
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 that 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.
During recuperative braking, electrical energy is generated from mechanical energy. The power supply/recuperation of the energy is implemented via the power inverter integrated in the power electronics control unit.
In the case of vehicles with an electric drive, two different electric machine types are used:
- Asynchronous motors
- Permanently excited synchronous motors
Asynchronous motors
The rotor in the asynchronous motor does not turn simultaneously with the electric rotary field in the stator but instead asynchronously. The asynchronous motor, as an electric motor, runs more slowly than the rotary field of the stator but the asynchronous motor, as an alternator, runs more quickly.
In the operating range, the torque is proportional to the deviation of the speed; this is known as "slip".
The stator in the asynchronous motor comprises three coils or a multiple thereof. These are subjected to a three-phase current, which generates a magnetic rotary field.
The rotor turning in the stator is designed as a squirrel-cage rotor/cage rotor. The rotor conductor rods are shorted with each other at the ends in a ring-shaped arrangement. There is no electrical contact with the outside via brushes.
The rotor is connected directly to the output shaft via a transmission. The electrical connection is made via the power electronics control unit.
Permanently excited synchronous motors
The rotor of the permanently excited three-phase synchronous motor consists of permanent magnets and rotates synchronously with respect to the rotary field in the stator.
In contrast to the asynchronous motor, the rotor is not energized even during operation and so develops less heat.
As with the asynchronous motor, the rotor is connected to the output shaft via a permanently transmitted transmission without a mechanical separating point. The electrical connection is made via the power electronics control unit.
Electric vehicles
A vehicle can contain one or two electric machines. Each of these can be designed as an asynchronous motor with a cage rotor or as a permanently excited synchronous motor.
Hybrid vehicles
The electric machine is designed as a permanently excited synchronous motor. Depending on the model, the electric machine may be located in the drivetrain as follows:
- In automatic transmissions, in the transmission bell housing. There is a positive connection between the rotor and the engine separator clutch via the rotor carrier.
- Together with the engine separator clutch and the dual clutch in the coupling unit.
The design of the electric machine as a wet runner allows for optimum dissipation of rotor and stator heat loss.
In generator mode, the electric machine generates braking torque that decelerates the vehicle or places a load on the combustion engine. Depending on the model, the transmission of the torque from the electric machine depends on the position of the engine separator clutch.
| Additional basic functions | |||
| Rear axle electric drive unit, basic function | Model all with engine 177 with code MF10 (Hybrid vehicle (plug-in, PHFV)) |
GF08.10-P-4000A | |
| Electric machine rotor position sensor, basic function | Hybrid vehicles and electric vehicles with a synchronous machine | GF08.40-P-2002A | |
| Electric machine temperature sensor, basic function | GF08.40-P-2003A | ||
| Electric machine rotational speed sensor, basic function | Electric vehicles with an asynchronous motor | GF08.40-P-2004A | |
| Detailed information | |||
| Electric machine, detailed information | Model 293 with code MF01 (Electric motor) |
GF08.10-P-2500A | |
| Model 167 with code MF05 (Hybrid drive 85 kW-94 kW variant (incl. plug-in)) Model 213 as of model year 2021 with code MF05 (Hybrid drive 85 kW-94 kW variant (incl. plug-in)) Model 213 as of model year 2021 with code MF08 (Hybrid drive 75-84 kW VARIANT (INCLUDING PLUGIN)) |
GF08.10-P-2500B | ||
| Model 296 | GF08.10-P-2500D | ||
| Model 177, 247 with code MF08 (Hybrid drive 75-84 kW VARIANT (INCLUDING PLUGIN)) |
GF08.10-P-2500F | ||
| Component descriptions | |||
| Flectrical machine, component description | Model 206 with engine 139 Model 206 with engine 254 Model 206 with engine 654 |
GF08.10-P-2001C | |
| Model 223 with code MF10 (Hybrid vehicle (plug-in, PHFV)) |
GF08.10-P-2001A | ||
| Model 232 | GF08.10-P-2001F | ||
| Model 243 | GF08.10-P-2001B | ||
| Model 253.9 with engine 780 | GF08.10-P-2001RFW | ||
| Model 295 | GF08.10-P-2001F | ||
| Model 297 | GF08.10-P-2001D |