Week-6 Challenge: EV Drivetrain

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

Solution:-

There are 4 types of the power converter.

1. AC-DC Converter:- This converter is used to convert AC into DC. This Converter is used in a charger where the AC power supply is converted into DC and stored in a battery.
2. DC-AC Converter:- This converter is used to convert AC into DC. This Convertor is used as an inverter. Where the DC current of the battery is converted into AC.
3. DC-DC Converter:- This converter is used to convert DC into DC for low power consumption. It can reduce the higher voltage to lower voltage and higher current into lower current or vice versa. In EV this is used for signal cable. The voltage of the battery is very high in EV, But to run the headlight and music player. We need low voltage and current.
4. AC-AC Convertor:-This convertor is used to convert AC into AC for low power consumption. It can reduce the higher voltage to lower voltage and higher current into the lower current.

2. An Electric Vehicle's powertrain with a 72V battery pack is 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 the duty cycle is 70%?

Solution:-

Voltage Across Motor Terminal:-

Vt = battery voltage * duty cycle

Vt = 72*0.7

Vt = 54.

Here Kϕ is taken as Kq.

Steady State Speed = 38.91 rad/sec

Simulink Model:-

Motor:-

Vehicle Load:-

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

ω = V/Kϕ -Ra/Kϕ^2 *T

Here Kϕ = Kq

4. Refer to the blog below topic:

Induction Versus DC brushless motors by Wally Rippel, Tesla

https://www.tesla.com/blog/induction-versus-dc-brushless-motors

Explain briefly the author's perspective.

Solution:-

The author basically wants to explain in the 1st paragraph that no engine is the best performer. Every vehicle has its own purpose and is designed for specific conditions. Here author emphasis on Ac Induction motor and BLDC (Brushless DC) motor. He wants to say, both the motors have some limitations. Where the BLDC motor is not efficient but the induction motor is also difficult to control. There is no winner. The author says DC brushless drives will likely continue to dominate in the hybrid and coming plug-in hybrid markets.