Week-6 Challenge: EV Drivetrain

1. AC - DC converter (On Board charger ) :

AC to DC converters are most commonly used in Plug-in Hybrid Electric Vehicles (PHEV) & Plug-in Electric Vehicles (PEV).

DC-DC converters :

DC-DC converters can be used to interface the elements in the electric power train by boosting or chopping the voltage`phi` levels .

DC -AC converter (Inverter) :

The DC -AC converter is required to convert the DC power to a suitable ac power for the electrical machine.The power output from the battery pack (DC current)is converted using inverter to be used in electrical motor (AC Current).

2.

An Electric Vehicle's powertrain with 72V battery .

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

..........eq (1)

What is EV steady state speed if duty cycle is 70%?

solution :

Duty cycle =70 % =0.7

actual voltage =0.7*72 =50.4 v

we Know torque eq for motor ,

T = (VkØ)/R_a –((kØ)² /R_a).w

T = (50.4 -0.7)/0.5 –((0.7)2/0.5).w

T = 70.56 -0.98 .w ………..eq(2)

solving eq 1 & 2

comparing both torque of vehicle and torque of motor .

24.7 +(0.0051).W^2=70.56 -(0.98).w

0.0051w^2 + 0.98 w-45.86 = 0

solving this quardratic equation we get .

w =38.915 rad/sec and neglet (-) value of w

so, the EV steady state Speed ifduty cycle is 70 % = 38.915 rad/sec

3. Develop a mathematical model of a DC Motor for the below equation using Simulink.

ω= V/Kϕ -Ra/Kϕ^2 .T

4.

In the begining author describes the dominance of internal combustion Engines (ICS) in the world of automobile industry and also discuss differance type of engines.He explane that all enginers were similar and it was up to user to select according to there requirement .he also speaks about the induction motor and brushless DC motor and presents his view that this two technology will be widely used for the coming years.

• then he explains the working of both 3-phase induction motor and brushless DC motor.
• Now the author has done comparison between this two technologies and started some advantage and disadvantages of each .
• Indcuction motor have some advantages like : it has no magnets .the motor has the ability to start under load .No inverter is needed .some disavvantages of induction motor are : they cannot operate from DC ;AC is must .shaft speed is proportionate to line frequency,Hence when used the utility power they are constant speed machines .when operative from utility power ,they have limioted starting torque ans some what limited running peak torque capabilities ,when compared to DC type machines.
• Brushless DC motor have some finally the author could not choose which drive the than the other but makes it clear that DC brushless drives will likely continue to dominate hybrid and coming plug in hybrid markets,and that induction drives will likely maintain dominance for the high performance for the high performance pure electrics.