Week-11 Challenge: Braking

EV LIVE BATCH 21

QUES.1

defined drive cycle is:

%program to calculate breaking energy for defined driving cycle

clear all
close all
clc

mass = 1000;                %mass of the vehicle in kg
T = velocityandtime(:,1);   %time period
V = velocityandtime(:,2);   %velocity data in m/s

for i = 1:(length(velocityandtime)-1);
    if V(i) > V(i+1);
        BE(i) = 1/2*(mass)*(V(i)^2 - V(i+1)^2);  %formula of breaking energy
    end
end
    fprintf('total braking energy is %d',sum(BE));
    fprintf('average braking energy is %d',mean(BE))
    
    %plotting the results
    figure(1)
    subplot(2,1,1)
    plot(t,v,'linewidth',3,'color','g')
    xlabel('time(s)')
    ylabel('Velocity(m/s)')
    title('DRIVECYCLE')
    
    subplot(2,1,2)
    plot(BE,'linewidth',3,'color','r');
    xlabel('Time(sec)');
    ylabel('braking energy')

QUES.2

According to the graphs above

We have two regions, namely constant torque and constant power

FOR ELECTRIC MOTOR

• high torque is available in the starting(k/a rated torque)
• motor reaches a maximum torque at base speed
• after base speed, torque start reducing
• The area having constant peak torque is known as(k/a) constant torque region, and area where torques decreases is k/s constant power region
• in constant power refgion at high speed there is very less torque, and is not possible to develop high braking torque in this region

It is because POWER = Torque* Speed

If both torque and speed is increased, the power will increase exponentially and will drain the battery very fast.

1. Electrical braking systems are used for controllinh speed and mechanical breaking is used for emergency stopping or for parking.
2. Mechanical breaking results in wear in the braking components and requires regular maintenance, whereas electrical braking does not
3. Electrical braking system cannot be used as a safety device. Most systems will require a mechanical braking system as a backup safety device.

There are two ways of applying the combination of brakes

SERIES - regenerative braking and frictional braking are apply one by one.

PARALLEL - regenrative braking and frictional are applied at the same time.