Week-6 Challenge: EV Drivetrain
STUDENT OF BATCH 16 ONLINE CLASS
1. Which types of power converter circuits are employed in electric and hybrid electric vehicle?
a) AC/DC converter- At the plug in point. Used in Plug-in Hybrid Electric Vehicles and Plug-in Electric Vehicles.
b)DC/DC converter - To chop the voltage levels and connect auxillary units, like infotainment systems, viper, light, door windows, sensors, boost fuel cell voltage and to regulate the DC-link voltage, to interface supercapacitors.
c) DC/AC converter(Inverter) - To connect energy source to motor, interior heating, connect to BLDC.
2.
An Electric Vehicle's powertrain with 72V battery pack in shown in the diagram below. The duty ratio for acceleration operation is 'd1' and for the braking operation the duty ratio is 'd2'.
The other parameters of the electric vehicle is given below,
Motor and Controller Parameters:
Rated Armature voltage= 72 V
Rated armature current= 400 A
Ra= 0.5Ω, KΦ= 0.7 Volt second
Chopper Switching frequency= 400 Hz
The vehicle speed-torque characteristics are given by the below equation
What is EV steady state speed if duty cycle is 70%?
ANSWER:
Vehicle output voltage = Va*duty cycle = 72*0.7 = 50.4v
Torque equation,T =(v-wk`((v-wkphi)kphi)/(Ra)`
T = (50.4-0.7w)*0.7/0.5
= 70.56-0.98w.......................... Equation 1
It is given in question Tv= 24.7+0.0051w^2............ Equation 2
COmparing equation 1 and 2 we get
70.56-0.98w = 24.7 +0.0051w^2
Rearranging this
0.0051w^2+24.7w-45.86=0
We can solve the equation by finding the roots
we get two values for`w`
`w=38.95`rad/sec and `w= -231.72`rad/sec
Since the rotation is in the forward direction w =38.95rad/sec
EV steady state speed for 70 percent duty cycle is 38.95*9.54 =371 rpm.
3.
Develop a mathematical model of a DC Motor for the below equation using Simulink.
ω">ω= V/Kϕ">ϕ -Ra/Kϕ">ϕ^2 .T
Model is given below
The ouput waveform obtained is
https://drive.google.com/file/d/1c1OryydMtZioAD0oPyR3gX5gzq_fg82g/view?usp=drivesdk
4.
Refer to the blog on below topic:
Induction Versus DC brushless motors by Wally Rippel, Tesla
Explain in brief about author’s perspective.
According to author,
- There are no single best engine in the world, but there exists multiple types of engines as per the requirements.
- With time the technologies have been changed, newer things have replaced the older things. But according to him the existing brushless dc motor and induction motor remains in the world for long time.
- Brushless DC motor require inverters to control current, without it the machine will be useless.
- Unlike, brushless DC motor, Induction motor has no magnet in the rotor and it produces rotating magnetic field.
- Induction motor basically operated based on induction and it produces the required torque.
- Also unlike BLDC which requires an inverter for producng torque when directly connected to 3-phase power, induction motor doesnot need inverter and has the ability to start under load.
- Both have losses, inorder to reduce them parameters have to be changed accordingly.
- But induction motors with smart inverter have advantage over BLDC.
- Induction motor has limitations like- cannot operate in DC, constant speed machine and they have limited starrting torque when operated direclty from supply.
- Both these motors have applications in EV and HEV. But in future there are chances they work together since they have similar hardware components.