2.1.2　Conceptual Illustration of a General EV Configuration

Text（课文）

A modern electric drive train is conceptually illustrated in Figure 2.3.The drive train consists of three major subsystems:electric propulsion，energy source，and auxiliary.The electric propulsion subsystem is comprised of the vehicle controller，the electronic power electronic converter，the electric motor，mechanical transmission，and driving wheels.The energy source subsystem involves the energy source，the energy management unit，and the energy refueling unit.The auxiliary subsystem consists of the power steering unit，the hotel climate control unit，and the auxiliary power supply.

Figure 2.3　Conceptual illustration of a general EV configuration

Based on the control inputs from the accelerator and brake pedals，the vehicle controller provides proper control signals to the electronic power converter，which functions to regulate the power flow between the electric motor and energy source.The backward power flow is due to the regenerative braking of the EV and this regenerated energy can be restored into the energy source，provided the energy source is receptive.Most EV batteries as well as ultracapacitors and flywheels readily possess the ability to accept regenerative energy.The energy management unit cooperates with the vehicle controller to control the regenerative braking and its energy recovery.It also works with the energy refueling unit to control the refueling unit and to monitor the usability of the energy source.The auxiliary power supply provides the necessary power with different voltage levels for all the EV auxiliaries，especially the hotel climate control and power steering units.

There are a variety of possible EV configurations due to the variations in electric propulsion characteristics and energy sources，as shown in Figure 2.4.

a.Figure 2.4（a）shows the configuration of the first alternative，in which an electric propulsion replaces the IC engine of a conventional vehicle drive train.It consists of an electric motor，a clutch，a gearbox，and a differential.

b.With an electric motor that has a constant power in a long speed range，a fixed gearing can replace the multispeed gearbox and reduce the need for a clutch.This configuration not only reduces the size and weight of the mechanical transmission，it also simplifies the drive train control because gear shifting is not needed.

c.Similar to the drive train in（b），the electric motor，the fixed gearing，and the differential can be further integrated into a single assembly while both axles point at both driving wheels.The whole drive train is further simplified and compacted.

Figure 2.4　Possible EV configuration

（a）conventional driveline with multigear transmission and clutch；（b）single-gear transmission without need of a clutch；
（c）integrated fixed gearing and differential；（d）two separate motors and fixed gearing with their driveshaft；
（e）direct drive with two separate motors and fixed gearing；（f）two separate in-wheel motor drives

d.In Figure 2.4（d），the mechanical differential is replaced by using two traction motors.Each of them drives one side wheel and operates at a different speed when the vehicle is running along a curved path.

e.In order to further simplify the drive train，the traction motor can be placed inside a wheel.This arrangement is the so-called in-wheel drive.A thin planetary gear set may be employed to reduce the motor speed and enhance the motor torque.The thin planetary gear set offers the advantage of a high-speed reduction ratio as well as an inline arrangement of the input and output shaft.

f.By fully abandoning any mechanical gearing between the electric motor and the driving wheel，the out-rotor of a low-speed electric motor in the in-wheel drive can be directly connected to the driving wheel.The speed control of the electric motor is equivalent to the control of the wheel speed and hence the vehicle speed.However，this arrangement requires the electric motor to have a higher torque to start and accelerate the vehicle.

New words and expressions（单词和短语）

1.New words（单词）

2.Expressions（短语）

Notes to the text（难点解析）

★1.Based on the control inputs from the accelerator and brake pedals，the vehicle controller provides proper control signals to the electronic power converter，which functions to regulate the power flow between the electric motor and energy source.基于来自加速和制动踏板的控制输入，车辆控制器向电力电子变换器给出正确的控制信号，变换器行使控制电动机与能源之间的功率流的功能。

Exercises（练习）

◆1.Translate the following passages（expressions）into Chinese（英译汉）

（1）It consists of an electric motor，a clutch，a gearbox and a differential.

（2）With an electric motor that has a constant power in a long speed range，a fixed gearing can replace the multispeed gearbox and reduce the need for a clutch.

（3）conventional vehicle drive train

（4）the power steering unit

◆2.Translate the following passages（expressions）into English（汉译英）

（1）电力电子变换器

（2）车内气候控制单元

（3）为进一步简化驱动系，牵引电动机可安置在车轮内。

◆3.Directions:Answer the following questions briefly according to the text

（1）What does the drive train consist of and how do they work？

（2）What are the possible EV configurations？

Reading material（阅读材料）

The clutch and gearbox may be replaced by an automatic transmission.The clutch is used to connect or disconnect the power of the electric motor from the driven wheels.The gearbox provides a set of gear ratios to modify the speed-power（torque）profile to match the load requirement.The differential is a mechanical device（usually a set of planetary gears），which enables the wheels of both sides to be driven at different speeds when the vehicle runs along a curved path.