Chapter 5　Electric Propulsion Systems

Text（课文）

Electric propulsion systems are at the heart of EVs and HEVs.They consist of electric motors，power converters and electronic controllers.The electric motor converts the electric energy into mechanical energy to propel the vehicle or vice versa，to enable regenerative braking and/or to generate electricity for the purpose of charging the on-board energy storage.The power converter is used to supply the electric motor with proper voltage and current.The electronic controller commands the power converter by providing control signals to it，and then controls the operation of the electric motor to produce proper torque and speed，according to the command from the driver.The functional block diagram of an electric propulsion system is illustrated in Figure 5.1.

Figure 5.1　Functional block diagram of a typical electric propulsion system

The choice of electric propulsion systems for EVs and HEVs mainly depends on a number of factors，including the driver's expectation，vehicle constraints，and energy source.The driver's expectation is defined by a driving profile，which includes the acceleration，maximum speed，climbing capability，braking，and range.The vehicle constraints，including volume and weight，depend on the vehicle type，vehicle weight，and payload.The energy source relates to batteries，fuel cells，ultracapacitors，flywheels，and various hybrid sources.Thus，the process of identifying the preferred feature and package options for electric propulsion has to be carried out at the system level.The interaction of subsystems and the likely impacts of system trade-offs must be examined.

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.The power converter is used to supply the electric motor with proper voltage and current.功率变换器用来对电动机提供特定的电压和电流。

★2.The driver's expectation is defined by a driving profile，which includes the acceleration，maximum speed，climbing capability，braking，and range.驾驶员的期望值由包括加速性能、最高车速、爬坡能力、制动性能和行驶里程在内的行驶循环予以定义。

Exercises（练习）

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

（1）Electric propulsion systems are at the heart of EVs and HEVs.

（2）The electric motor converts the electric energy into mechanical energy to propel the vehicle.

（3）functional block diagram

（4）mechanical energy

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

（1）再生制动

（2）电能

（3）这些系统由电动机、功率变换器和电子控制器构成。

Reading material（阅读材料）

The electronic controller can be further divided into three functional units—sensor，interface circuitry and processor.The sensor is used to translate the measurable quantities，such as current，voltage，temperature，speed，torque，and flux，into electric signals through the interface circuitry.These signals are conditioned to the appropriate level before being fed into the processor.The processor output signals are usually amplified via the interface circuitry to drive power semiconductor devices of the power converter.