Week-11 Challenge: Braking
Question 3
contour plots of efficiency and Matlab code attach.
% program to plot the countour effieciency for electric motors
% x axis relates to motor speed
% Y axis relates to Torque
%define range
X=linspace(1,1000);% rad/sec
Y=linspace(1,250)% N.m
%losses in the motors
%copper loss
kc=0.2;
%iron losses
ki=0.008;
%windage losses
kw=0.00001
%constant losses
C=20;
%meshing grade
[X,Y]=meshgrid(X,Y);
% ouptput power P= torque*speed
Ouput=(X.*Y);
% to find the losses
%copper loss
A=(kc*Y.^2);
%iron losses
B=ki*X;
%windage losses
D=kw*X.^3;
% find the total power losses
% input power= output power+ losses
Input=Ouput+A+B+D+C;
%speed*torque
Ouput=(X.*Y);
%now find efficiency
Z=Ouput./Input;
%we we different speed torque value.
V=[0.70:0.05:0.90];
box off
grid off
contour(X,Y,Z,V);
xlabel('speed rad/sec');
ylabel('torque N.m');
hold on
%plot countour for KW motor.
V=[8000,10000];
contour(X,Y,Ouput,V);
hold off
title('speed torque contour ')
xlim([71 896])
ylim([10 216])
Obersevations
the inner cicrcle has the greast efficiency then any other.
as the speed increases more then the limit efiiciency decreases.
different efficiency is observed at diffrent speed and torque. (in the box blue color)
Question 2
a
Brake torque is the force applied at the brake wheel to stop the motion of the moving vehicle. Unfortunately, Electric motor cannot develop braking torque at higher speed similar to starting because Braking torque applied in theopposite direction of the rotation.
Regenerative braking takes place when the speed of the motor exceeds synchronous speed,so the motor becomes the generator and generates the
electrical energy which can be stored in the battery and supply to load.
the main reason that braking torques is not as same as starting torque bcz the torques generated when the vehicle is at hihg speed or hihg accerlartion in not equal to the vechile is at peak deceleration.
Motor is operated in above base speed,that is why the braking torque of motor is not as high as accerleration.
How electric and mechanical brakes are coordinated?
there are 2 types of braking system in th EV one is electric braking and the other is Mechanical braking.
Both are arrange in the series and parallel.
In series arragement both brakes work one after the other . not at same time .
in parallel arrangement both brakes works saimultenously at a time.
But only Regerative braking takes place in low speed not at high speed.
beacause at low speed electronic brakes are used more then the mechanical
where as at high speed mechanical beakes are used frequenty. regeneration take place here but low as compare to low speed .
this Design was invented by NISSAN group of compinies and can be seen in the model NISSAN LEAF >
Braking graph of NISSAN
Question 1
- For a defined driving cycle, calculate the energy required for braking.
drive cycle imported .
driving cycle sheet 4 to be applied.
