Assignment Week - 5

Question - 1

Implement DC machine torque speed characteristics equations in MATLAB script file. It asks user to input data and plots speed (RPM) versus torque (Nm). Submit the .m file for evaluation and attach the screenshots of all the required plots

DC Machine Torque Vs Speed Characteristic Equation is as given below,

Values that we require for Plotting the Speed Vs Torque Graph,

Speed of motor, Supplied Voltage Value, Armature Resistance, Back EMF, Motor Constant and Flux.

Speed of the Motor - 82

Supply Voltage - 24

Ra - 0.0130

Eb - 1

Km_Phi - 0.0131

Motor Constant - Km_Phi = 60/(2*3.142*m_s)

Torque using Motor Characteristics - T = ((Km_Phi*Es)/Ra)-((((Km_Phi)^2)/Ra)*Speed)

Applying all the same details in Matlab - 

clear all

close all; clc

%Speed in radian

Speed = (0:20:240)

%Motor Speed in (RPM/V)

m_s = 82

%Supply voltage

Es = 24

%Armature Resistance in Ohm

Ra = 0.0130

�ck emf

Eb = 1;

%Motor Constant and Flux

Km_Phi = 60/(2*3.14*m_s)

�lculating Torque as per the equation

T = ((Km_Phi*Es)/Ra)-((((Km_Phi)^2)/Ra)*Speed)

%Converting Speed to RPM

Speed = Speed*(60/(2*3.14));

%Plotting Speed VS Torque

plot(Speed,T);

xlabel('Speed (RPM)')

ylabel('Torque (N-m)')

title ('Torque Speed Graph')

axis([0 2400 0 240])

�lculating Current in Ampere

I = (Es-Eb)/Ra

�lculating Maximum torque in (N-m)

Tmax = Km_Phi*I

The Graph for the same is as mentioned below,

Question - 2

How can you distinguish between power cables and signal cables in wiring of an electric vehicle?

Power cables - Power Cables are generally a combination of wires and conductors that are held together for transmitting the Electrical Power. They have their applications in Buildings, Commercial Infrastructures, Vehicle Wiring and all aspects where power transmission plays a vital role. There are many types of Power Cables such as Co-axial Cable, Ribbon Cable, Twisted Pair Cable, Shielded Cable and many others. 

Application in Cars :- In cars Power Cables are used to transmit the power from one source to another as the Batteries are the Power House of the car and the same has to be transmitted throughout the car for operations. There Power Cables are used. Power cables are generally thick in diameter as their major application could be to transmit high power/low power. If it is an EV/HEV car where the Battery is providing power to the Motor for gaining movement their the Main Cable has to be very thick in diameter and for other normal applications the thickness of the cables are moderate.

Signal Cables - Signal cables that transmit the information or the signals from one end to the other carry almost no current. For an example the Telephone Cable, the Internet CAD 6 or other cables that carry no cables are are moulded in the form of Coaxial Cables they can not generally be referred as signal cables but they have more or less the same property. They are thin in diameter.

Application in Cars :- The Signal Cables are used for send the information from the sensor to the ECM or any other control modules they carry no current and are thin in diameter. They are used for transmitting data and modulating the CAN BUS.

How can we distinguish between them :- 

Majorly these qualities would be common in both the Power Cables and Signal Cables as mentioned below,

Question - 3

What voltage levels are considered as high & low for a battery pack of electric vehicle?

Generally the Voltage for the batteries used in HEV and EV are as below, 

Voltage Level	Minimum	Maximum
HEV/Plugin Hybrid	100 V	200 V
EV	400 V	800 V
Traditional	12 to 24 Volts
Mild Hybrid	48 V

What makes the battery manufacturer to consider the High and Low Voltage or what parameters are considered to grade the battery for High and Low Voltage are, 

• As we know the battery packs are a combination of several parellel cells which are formed to a battery pack. The lowest voltage through which the constant charge is passed on and is comfortably accepted by the cells together is majorly to be considered for low and high voltage. 
• Battery Temperature plays a vital role for the High and Low Voltage considerations
• Type of Battery used
  
  
• The high peak point where the vehicle can be charged and does not effect drastically on the life of the battery has to be considered. 
• Type of operation from the battery.
  
  
• Charge to be withdrawn from the battery and at what state the steady flow has to be achieved. 

In all these manners the Low and High Voltage are designated to a battery, as we know Voltage is what makes the Electric Charge move. So the constant movement and maintaining the sorroundings has to be decieded which is monitored by BMS Battery Management System.