Week-6 Challenge: EV Drivetrain

1. Which types of power converter circuits are employed in electric and hybrid electric vehicle?

There are basically 3 type of power convertor in Electric and Hybrid electric vehicle,

• AC-DC converter
• DC-AC converter
• DC-DC convertor

AC-DC Converter: -

• AC/DC converter which supplies electric power from a commercial power system to an onboard high-voltage battery.
• This converter is used for charging the vehicle
• As battery stores energy in the form of DC, AC-DC power converter is used
• They are generally used in Plug-in Hybrid Vehicle and Electrical Vehicle.
• This converter also called rectifier.

DC-DC Converter: -

• As in vehicle there are also requirement of low DC voltage like Indicator, head lights, signal generators…
• This low DC voltage is provided with DC-DC Converter.
• In battery there is high DC voltage this convert to low DC voltage with help of DC-DC Converter.
• DC-DC Converter also known as Chopper

DC-AC converter: -

• This type of converter is used in supplying power to motor.
• In motor power required is AC but in battery there is DC Voltage so, from this converter DC voltage is converter into AC voltage.
• This converter also known as Inverter.

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'.

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

Parameters of the electric vehicle are given below,

Motor and Controller Parameters:

• Rated Armature voltage= 72 V
• Rated armature current= 400 A
• Ra= 0.5Ω, Kphi= 0.7 Volt second
• Chopper Switching frequency= 400 Hz

The vehicle speed-torque characteristics are given by the below equation

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

ω = V/Kϕ -Ra/Kϕ^2. T

4. Refer to the blog on below topic: https://www.tesla.com/blog/induction-versus-dc-brushless-motors

Explain In brief about author’s perspective.

• There is no one best engine type, rather there are different types of engines to suit personal requirements, such as price and performance.
• In old time in EV there is lead acid batteries, DC brush motors, and contactor controllers. But now it’s all replace by new innovation and technology like Lithium batteries, DC brushless or Induction motor, and modulating inverter.
• There is a bigger concern regarding the stable use of these elements mentioned above over the future.
• The Author discusses about two new technology DC brushless drives and Induction Motor
• He thinks brushless motor are useless motors because it required inverter
• He also thinks Induction motor way better than DC brushless motor. Because of the ability to start under load.
• He also says that Induction motor has some severe limitations, like cannot operate from DC.
• He says that induction machine is more difficult to control.
• He also compares upcoming future trend with DC brushless motor and induction motor.
• In last he concludes 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 the high-performance pure electrics.