Week-6 Challenge: EV Drivetrain

- AIM :

- To get to know the types of converter used in HEV and EV vehicles .

- To find the speed using torque - speed relation .

- To get to know about induction and DC brushless motors .

- OBJECTIVES :

- To get to know information on converters for HEV and EV vehicles .

- Find the speed using Torque - speed expression .

- Try to find the best option for motors HEV or EV vehicles .

- METHOD :

Q.1 Which types of power converters circuits are employed in an electric and hybrid electric vehicle ?

- A motor drives consist of a power converter and the controller . The power electronics converter handles the flow

Bulk power from the source to the motor input terminals . The controller process the command input and the feedback

information to generate the switching signals for power converter semiconducter switches .

- The power converter can be a DC drive supplying of a DC motor on a AC drive supplying on AC motor .

- A DC to DC converter in its basic from converts unregulated DC input voltage at a certain level to regulated DC output

Voltages at a different level with very high conversion efficiency . These are operated at very high frequency .

The switches are turned ON and OFF by pulse width modulation (PWM) .

- The power converter is made of high power fast - acting semiconducter devices , such as a bipolar junction

Transistor .These are some other transistor such as MOSFET , IGBT , SCR , GTO MCT . These devices are used as

on-off electronics swithces to be converts the fixed supply voltage in to a variable voltage and variable frequency

Supply .

- All these devices have a control input gate or base through which the devices are turned on and off as per the command

Generated by the electronics controllers.

- These are two types of step converters , when a low voltage input converted in to a high voltages output is a step - up

Converter . whereas when a high voltages input is converted into a low voltages output is a step down converter .

The figure is showing a DC - DC converter for Electric vehicles .

WAVEFORM : - DC CHOPPER DRIVE AND AC DRIVE

- Power Converters

- AC/DC CONVERTERS TO DC/DC CONVERTERS : -

- AC/AC CONVERTERS TO DC/AC CONVERTERS : -

Q.2 An Electric vehicle's powertrain with 72V Battery pack in shown in the diagram below .

The duty ratio for acceleration operation is 'd1' and for the braking operation the duty ratio is 'd2' .

The other parameter of the electric vehicle are given below ,

Motor and controller parameters :

Rated armature voltage = 72V

Rated armature current = 400A

T= torque

V = Armature voltage

R = resistence

w = speed/rad/sec

Compare the two equation :

24.7+0.0051 *w^2 =((v*k)/R) - ((K^2)*w/R)

24.7 +0.0051*W^2 = (72*0.7*0.7)/0.5 - (0.7^2/0.5)*w=24.7+0.0051*W^2

70.56 - 0.98*w - 8992.15 =0

In order to find the roots use following formula :

USE QUADRATIC EQUATION :

As the speed value can not be negative

W = 38.93 rad/sec .

Q.3 Explain in brief about the author's perspective .

OR ,

Induction motor Vs DC brushless motor by wally Ripple , Tesla , Explain in brief about author's perspective.

The author writes this blog to entail the differences between the two most commonly used motor drives in the automobile

Industries the DC brushless motor drive and the induction motor drive . Ripple goes in to detail working about the differences

in construction working,and the between the two drives.However, with what he has written , he has not arrived at the con -

clusion , that one type is better then the other . in the last line in the opening paragraph , Ripple writes that.

'' There is no one best engine type '' and that is all a metter of personal preference when it comes too choosing as engine

it is in this same regard that he ends the block in split of both motor drives types having similarties , they also have

their benefits and backwards .

For DC brushless drives , we are told that their construction implement 2 or more permanent magnet at the rotor to

Generate a DC magnetic field .it also consist of stator core (made up of thin , stacked lamination) it also uses an inverter

For the current control . meaning that it cannot run on a DC power supply as the current direction has to be changed

Repeatedly in to maintain a constant torque .

- For the induction motor drive , there rotor has no magnet , but instead steel lamination with buried peripheral conducters

which form a 'shorted structures , it is the current in the current in the ststor winding that generates a rotating magnetic

Field that interacts with the rotor .

- Induction motor can be used directly with power from the mains and does not required any inverter to the start the drive

And generate the starting torque . it has to ability to start under the mains apply .

DC brushless drives use permanet magnets , and cannot change the strength of their magnetic field . it whould be

Desirable if they could .in different types brushless condition to be changes at a different level load through the dc

if user seeking a high performance with comparetively lesser costs , then the induction motor drive would be better

Suited of a DC brushless drive would be the smarter choice , both types have their places in the automobile industries

and will retain their relevence is their respective appliction .Ripple believes that due to the increasing performance of a

vehicles , one day both drives .

Ripple believe that performance due to the a new kind of hybrid that combines the characteristics of an ordinary

vehicle , e.g sedan with that of sports car .

• CONCLUSION : -

Implemented the power converter circuit characteristics of MATLAB program to easily implemented through

Hybrid electric circuit of power conveter to the low voltage of a battery.