Week-6 Challenge: EV Drivetrain

Q1)

1. Power converters in Electric and Hybrid Electric vehicles are considered as their power sources to the drivetrain of the EVs. In order to design highly efficient converters for the EVs power system, advanced DC/DC and DC/AC converters are required to adapt the output voltage and current levels with high power quality.
2. There are 3 types of converters which are widely used in an electric vehicle are :- 

1. AC – DC Converter
2. DC - DC Converter
3. DC – AC Converter

Q2)

GIVEN:-

Rated Armature Voltage = 72V

Rated armature current = 400A

Armature resistance = 0.5ohm

Motor constant = 0.7 volt sec

Chopper switching frequency= 400Hz

Duty cycle = 70%w

Sol :-

Vehicle output voltage is given by :-

Vehicle voltage (Vv)= Battery voltage * Duty cycle = 72 * 0.70 = 50.4 V

Vehicle torque eqn ;

Tv  = ((Vv – w*K@) * K@)/Ra

Tv = ((50.04 – 0.7 * w) * 0.7)/0.5 = 70.56 – 0.98*w

Tv = 24.7 + 0.0051*w^2

Solving these two equations,

70.56 – 0.98 * w = 24.7 + 0.0051 * w^2

We get a quadratic equation;

0.0051 * w^2 + 0.98 *w – 46.94 = 0

Since quadratic equation, we get two values of;

W=38.85 rad/s and w=-230.95 rad/s;

Steady state speed of vehicle= = 38.85 rad/s

Q3)

1. Author describes the dominance of internal Combustion Engines (ICE) in the world of automobile industry and also discuss different types of engines.
2. He explains that all engines were similar and it was up to the user to select according to their requirement.
3. He also speaks about induction motor and brushless DC motors and presents his view that these two technologies will be widely used for the coming years.
4. Then he explains the working of both 3-phase induction motor and a brushless DC motor.
5. Now the author has done comparison between these two technologies and stated some advantages and disadvantages of each.
6. Brushless DC motor have some advantages like: much less rotor heat is generated with the DC brushless drive.
7. The peak point energy efficiency for a DC brushless drive will typically be a few percentage points higher than for an induction drive.
8. Some disadvantages of Brushless DC motor are as machine size grows, the magnetic losses increase proportionately and part load efficiency drops.
9. Finally the author couldn’t choose which drive is better than the other but makes it clear that DC brushless drives will likely continue to dominate in the hybrid and coming plug-in hybrid markets, and that induction drives will likely maintain dominance for high performance pure electrics.