Week-6 Challenge: EV Drivetrain

Question - 1

First let us understand what are Power Electronics and Power Circuits,

Power Electronics and Power Circuits come into action where the varied Power Supply is required depending upon the application of user load. With this varied range of power output Power Electronics help in customizing the requirement in a manner where the Power Storage is at its maximum and the Energy Losses is minimum.

"Electronics applied to conversion and control of Electric Power"

There are different types of Power Circuits used for varied operations in the EV and HEV Vehicles.

The two different forms of the Power Circuits can be based upon Analog and Digital Control where analog refers to 

• Car Charger (Conversion from AC to DC)
• Motor Drive (Conversion from DC to AC) Induction
  
  

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Question - 2

As per the details given in the question, 

Motor and controller parameters, 

Rated Armature voltage = 72 V

Rated armature current = 400 A

Ra = 0.5Ω, 

KΦ = 0.7 V-s

Chopper Switching frequency = 400 Hz

The vehicle characteristics - TTR = 24.7 + 0.0051 w²

As we know the steady state of the vehicle here could be plotted on the graph of Speed vs Torque considering the Motor Torque and the Torque Load. Where the point intersect and are steady in state that speed is to be considered as the speed of the vehicle.

The code for the Matlab is mentioned below, 

>> %Calculating the Steady Speed of an EV at 70% Duty Cycle

clear all

close all;clc

%Armature Resistance

Ra = 0.5;

%Armature Voltage

Es = 72;

%Motor Constant & Flux Per Pole

Km_Phi = 0.7;

%Considering 70% of the Armature Voltage as the Duty Cycle

Es70 = 50.4;

%Angular Velocity

w = (0:0.1:100);

%Vehicle Characteristics

Tv = (24.7+0.0051*w.^2);

%Motor Characteristics

Tm = ((Km_Phi*Es70)/Ra)-((((Km_Phi)^2)/Ra)*w);

xlabel ('Speed (rad/s)')

ylabel ('Torque (Nm)')

title ('Steady State Speed @ 70%')

%Plotting Speed Characteristics

plot (w,Tv);

axis ([0 50 0 100])

hold on

%Plotting Speed againts Motor Characteristics

plot (w,Tm);

The steady speed is obtained at 38.915 (rad/s)

Converting the same to km/h = radians per second (rad/s) * radius of the wheel * 3.6

Considering MG ZS EV tyre specs for the radius of the wheel - 215/50 R17.

Width = 215

Height = 50% of 215 = 107.5 mm = 4.23"

Radial of the wheel = 17"

Radius of the wheel = Radius of Alloy + Height of the Wheel

= 8.5 + 4.23 = 12.73"

Converting the same back to m = 0.323342

Converting the same to km/h = 38.915 * 0.323342 * 3.6 = 45 km/h

The Plot for the same is attached below,

We have got the value of ω that is 38.915 rad/s 

Substituting the same value on the Torque Load/Vehicle Characteristics

TTR=24.7+0.0051*ω²

= 24.7+0.0051*(38.915)²

= 32.423

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Question - 3 

The blog by Wally Rippel majorly focuses and puts light on the Brushless DC Motor and the Induction Motor. 

Firstly, as we are aware that the Brushless DC Motors are majorly been used in the Hybrid Vehicles and contribute to the majority of the Automotive Vehicles. There is a difference of operation between both the Brushless DC Motor and the AC Induction Motor. The working principles for both are the same as there are the Copper Windings been used in the Induction motor apart from the Magnetic Poles and when we compare the rotor winding are differenciated but the Stator majorly remains the same as functionality. 

Back in 1989, a forerunner of the 3-Phase Induction Motor was been invented by Nikola Tesla and the contribution of Tesla Family for Electrifying plays a vital role in today's scenario. 

In terms of operation both Motors work on different principles, one working on the NP-SP Magnetic Fields and the other with the Magnetic Fields in the Copper Windings. Where size, power, torque and speed all play different role somewhere some aspects do not deliver its peak at major scenarios and on the other end it

does. 

The most important and vital points mentioned in the Blog are as mentioned below