Week-6 Challenge: EV Drivetrain

1)

The components used in EV and HEV can be understood by the layout shown below,

In the figure shown above, there are different components including a Fuel tank, Engine (in the case of Hybrid), Battery pack, Power Electronic converter, Traction motor, and Transmission.

The Power electronic converter can be further elaborated in the type of conversion of the supply type.

• AC to DC ----> Rectifier: It is used when the EV or HEV is to be charged from a general AC supply at our homes or charging stations. Just like UPS it will charge the battery pack by converting the AC supply to DC.

• DC to AC ----> Inverter: The battery after being charged has to supply power to the traction motor to move the EV and hence it requires AC supply for better results. Hence here inverter is used to feed the motor with an AC supply when we have DC as the stored supply option in the battery.

• DC to DC ----> Chopper and Converters: This converter is used to reduce the voltage level of the battery voltage to run the auxiliary system of the EV, such as headlights, music system, lights, etc.

Step-down chopper /Buck converter: This is mostly used in the above explanation, that reduces the voltage level of the battery pack to feed to the smaller, low voltage appliances.

Step-up chopper/Boost Converter: This is used in the case when the voltage level has to be raised for a certain application.

Unidirectional converter: This converter has the capability to converter i.e. step-up or step-down in one flow direction of the power supply, i.e. one input and only one output side.

Bidirectional converter: This converter is capable to change the voltage level from both sides of the circuit..

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2)

Given data ,

Battery pack in EV (Armature voltage)= 72 V

Armature current (Ia)= 400 A

Armature Resistance Ra = 0.5 Ω

Motor constant = 0.7 Vs

Chopper Switching frequency = 400 Hz

Duty cycle = 70% = 0.7

Actual Voltage (V) = 72*0.7 = 50.4 V

Now by using the Torque-speed equation for motor

--------- (1)

-----------(2)

We have a given equation

----------------(3)

At steady state

----------------(4)

Equating the equations

Solving the quadratic equation, we get

ω = 38.92 or ω = -231.07

So accepting the positive value

ω = 38.92 rad/s

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3) The Simulink Model for the equation is shown below

Explanation of Model:

• The Value of KΦ is found by dividing Back EMF by Speed range.
• Then according to the equation Supply voltage is divided by KΦ block output.
• Similarly the value of Ra as an input is divided by (KΦ)^2 and mutilplying by T.
• Then calculating the equation by the substract block.

The Parameters and the simulation were done on the DC model created in the week 5 assignment

%Torque Speed Characterstics of DC Machine

close all

clear all

clc

%array of Speed Omega (w) in rad/sec

w=linspace(0,1500,50);

N=(2*3.14*w)/60;

%Battery Supply Voltage

V=input('Enter the Battery Supply Voltage: ');

%Velocity Constant = No Load Speed/Supply Voltage

%which helps in Motor Sizing and Selection of Winding Parameters.

Vconstant=input('Enter the Velocity Constant Value : ');

Vnl=Vconstant*V; %No load Speed

%Back EMF

Eb=1;

%Armature Resistance

Ra=input('Enter the Armature Resistance Value (ohm) : ');

%Motor Constant

Mc=(Eb*60)/(2*3.14*Vconstant);

%Torque Equation

T=((V*Mc)/Ra)-(((Mc)^2)/Ra)*N;

%Armature Current

I=(V-Eb)/Ra;

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4)

Engines vary in this world of gas-powered automobiles. There is no one optimum engine type; rather, there are various sorts of engines to meet individual needs, including those related to cost and performance. The same is true for the drives of electric vehicles. Some driving components for electric vehicles could become stable or become obsolete in the near future.

Analysis:

The author tends towards the use of EV and its functioning. The author emphasizes on the comparative study of 3phase Induction motor and Brushless DC motor.

When it comes to pro and cons of Induction motor it has many. 3ph- IM can be started without any external mechanism, also at loaded condition. This motor doesn't have magnets hence mass of motor is less. Also in IM's case no inverter or converter is required for its operation.

With induction, losses do not always increase as machine size increases. Induction drives may therefore be the preferred strategy in situations when great performance is required.

He cited various disadvantages of induction motors, such as the inability to run on DC and the restricted starting torque and running peak torque capabilities they have while using utility power because shaft speed is proportional to line frequency.

Also in case of BLDC the main advantage that is mentioned by author is that it doesn't have any internal contact and hence the heat loss is less.

Conclusion:

The conclusion which can be drawn from the blog is that DC brushless motor will rule the hybrid and plug-in hybrid car markets. For high performance and pure electrics, induction motor drive will always be the dominant technology. Therefore, the author has not stated which of the two drives is clearly superior; instead, he has focused on the advantages and downsides of each drive.

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