EV Architecture,Components

EV-103

This course is presented as part of Evannex Universitya free, open learning environment that presents concise, video-based mini-courses for those who have interest in electric vehicles (EVs)

What is architecture?The components of an EV systemHow the components fit together into subsystemsHow the subsystems convert electric power into motive force for the vehicle

In the context of an electric vehicle the term architecture refers to:

>> The components of an EV system>> How the components fit together into subsystems>> How the subsystems convert electric power into motive force for the vehicle

In this Evannex U mini-course, well take a look a the basic elements of an EV architecture, and in the next mini-course in this sequence, well examine how these elements can be organized into alternative architectures.

BEV Architecture

The simplest of all EV architectures is the battery electric vehicle, the BEV.

In a BEV, there is a limited set basic components associated with the propulsion of the vehicle.

BEV Architecture

The simplest of all EV architectures is the battery electric vehicle, the BEV.In a BEV, there is a limited set of basic components associated with the propulsion of the vehicle.Looking at the diagram on your screen from left to right,- Electricity from the grid is conditioned by an charger (in orange) that may be part of the vehicle or a separate component.- The charger passes electricity to the battery (in yellow) - Energy stored in the battery is passed through control electronics (in grey) that moderate the energy flow and pass it to an electric motor- Regenerative braking (in green) translates kinetic energy of the cars forward motion into electricity and returns energy to the batteryLets take a look at each of these components in a bit more detail.

The BatteryThe Heart of an EVThe bigger and better the battery, the better the EVBigger? Not size, but storage capacity measured in kWhBetter? Not size, but recharge time measured in hours and minutes

In an earlier mini-course I mentioned that

>> the battery is the heart of an EV.

In fact,

>> the bigger and better the battery, the better the EV the higher its performance, the longer it's range, and the more utility it offers to the owner.

But what do we mean by bigger and better.

>> Bigger doesn't refer to the size of the battery, but rather to its storage capacity measured in kilowatt ours.>> Better refers to the batterys ability to recharge quickly as measured in hours and minutes.

Although battery storage capacity and recharge times have improved dramatically over the last decade, there is much to be done to improve them still further.

But even today, storage capacity and recharge times are sufficient and make EVs competitive with ICE vehicles.

The Electric MotorThe statorThe rotor Current creates a magnetic fieldAC causes field to vary between N and SThe rotor chases the magnetic field and rotates

Source: Tesla Motors

The physics of an electric motor is a bit beyond the scope of this mini-course. But a few basics are important.

>> Coils of copper wire run through a stack of thin steel plates and form a stator. >> The rotor is a steel shaft with copper bars running through it. It rotates, and ultimately, turns the wheels of the EV.

But what makes the rotor rotate?

>> The flow of alternating current into the copper windings of the stator creates a magnetic field.>> Alternating current causes the field to vary between N and S, appearing to move in a circular path>> The rotor chases the magnetic field and rotates as a consequence.

Of course, theres a bit more to it than that, but that should give you the general idea.

The Electric MotorSmaller number of moving parts, leading to better reliability over timeInstant torque (power) and variable speedmeaning no need for a transmissionVery efficient: 80 90% vs. 20 30% for ICEZero emissions

The electric motor is the workhorse of modern industry, and will soon become an important motive force in the car industry.

>> Electric motors are remarkably simple, have very few moving parts, and have extremely high reliability, partly due to the smaller number of moving parts.

>> Electric motors have a square torque curve, meaning that you get impressive acceleration off the line

And they are variable speed, meaning there is no need for a transmission, eliminating hundreds of parts that can and sometimes do fail in an ICE vehicle

>> Electric motors are very efficient.

Efficiency is the degree to which a motor converts input energy to output power. For electric motors the efficiency is quite high -- in the range of 80 to 90%. The efficiency of Internal combustion engines is only in the 20 to 30% range -- a significant difference.

>> Finally electric motors have zero emissions.

Electric MotorBenefitsthe electric motor can be electronically modifiedengine performance enhancements can often be achieved with software and control electronicsan electric motor rotates around a single axisweve been building and using electric motors for over 100 years

There are even more benefits:

>> the electric motor can be electronically modified enabling it to become a generator, allowing regenerative braking that converts the forward motion of the car (called kinetic energy) into electricity that recharges the battery

>> engine performance enhancements can often be achieved with software and control electronics

>> an electric motor rotates around a single axis, leading to reduced vibration and longer life.

>>weve been building and using electric motors for over 100 yearsthis isnt bleeding edge tech

Control Electronics

The controller performs the following functions:transforms DC to AC (when required) and regulates the energy flow from the battery. reverses the motor rotation converts the motor into a generatorThe electric vehicle controller is the electronics package that operates between the batteries and the motor to control the electric vehicle's speed and acceleration, much like a carburetor does in a gasoline-powered vehicle. U.S Department of Energy

The US DoE describes the control electronic for an EV in the following manner:

>> The electric vehicle controller is the electronics package that operates between the batteries and the motor to control the electric vehicle's speed and acceleration, much like a carburetor does in an older gasoline-powered vehicle.

>> The controller performs the following functions:- transforms DC current from the battery into AC (for AC motors) and regulates the energy flow from the battery. - reverses the motor rotation (so the vehicle can go in reverse) - converts the motor into a generator so that the kinetic energy can be used to recharge the battery during regenerative braking

Regenerative BrakingWhen a car is moving, it has kinetic energyWhen you brake a conventional car, the kinetic energy is dissipated as heat (through the brakes) and the car slows and stopsWhen you brake an EV, the kinetic energy is transformed into electrical energy and used to recharge the battery

>> To get geeky for a moment, kinetic energy is a function of the cars mass and its velocity squared. The mass of any car is huge, and the when a car is going fast, its velocity squared is also significant. That means theres a lot of kinetic energy to capture.

>> Thats why your brake pads become very, very hot as you brake. Thats unfortunate, because the kinetic energy of an ICE car is lost as heat, when it could be re-used.

>> The transformation is really quite simple. The electric motor is electronically switched and becomes a generator that produces current that is sent back to the battery, recharging it.

But be careful with your assumptions here. Not all of the kinetic energy is converted into current, because there are losses in the conversion. If there were no losses, EVs would be perpetual motion machinesand thats impossible. But EVs do capture as much as 40 50 percent of the cars kinetic energy and reuse it. And thats pretty cool.

As well see in another EVU mini-course, it also makes driving an EV a bit different. Shockingly, you rarely need to hit your brakes!

SummarySimple architectureRelatively few component elementsAnd that means Fewer parts that can failConsiderably less complexityLower maintenance costs and less frequent maintenance visits

Lets summarize .

>> The basic EV architecture is a simple architecture in automotive terms. Thats not to say that EVs dont deliver sophisticated techthey do!

>> But the component parts of the architecture are relatively small in number.

>> And that means

>> Fewer parts that can fail>> Considerably less complexity>> Lower maintenance costs and less frequent maintenance visits

a free study guide for all EVU mini-courses is available for download from our website For a complete list of mini-courses and the study guide, visit: www.evannex.com

OlharesRouletBeats d'Amor, track 12014-05-18T14:02:41118051.055OlharesRouletBeats d'Amor, track 12014-05-18T14:02:41118051.055