Week-6 Challenge: EV Drivetrain

1.

1.DC to AC Converters:

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

2.AC to DC Converters:

An AC to DC converter is also called a rectifier.AC to DC converters are most commonly used in Plug-in Hybrid Electric Vehicles (PHEV) & Plug-in Electric Vehicles (PEV). These vehicles get their propulsion power from an external electricity source (charging stations) which is alternating current. The battery needs to be charged using a direct current source. For this purpose, AC to DC converter is employed in a PHEV & PEV.

3.DC to DC Converters:

DC-DC converters can be used to interface the elements in the electric power train by boosting or chopping the voltage levels. By introducing DC/DC converters one can choose the voltage variation of the devices and the power of each device can be controlled. The power of the DC/DC converter depends on the characteristics of the vehicle.

2.

Given parameters:

Rated Armature voltage= 72 V

Rated armature current= 400 A

Ra= 0.5Ω, KΦ= 0.7 Volt second

Chopper Switching frequency= 400 Hz

Tv=24.7+(0.0051)ω2..............equation(1)

Duty cycle=70%=0.7,

therefor, Actual voltage=0.7*72=50.4V

We have torque equation for motor,

T=VkϕRa−((kϕ)2Ra)ω

T=(50.4*0.7*0.5)−((0.7)2*0.5)ω

T=(70.56−0.98)ω..................equation(2)

solving equation (1)&(2),

comparing both torque of vehicle and torque of motor,

24.7+(0.0051)ω^2=70.56−(0.98)ω

0.0051ω^2+0.98ω−45.86=0

by solving this by quadratic equation we get,

ω=38.915radsec and ω=−231.072radsec

So, the EV steady state speed if duty cycle is 70% = 38.915 rad/sec or 371 RPM

3. ω= (V/Kϕ -Ra/Kϕ^2 ).T

here we consider,

v=50.4

Kϕ=0.7

Ra=0.5

Output:

A file is attached.

4.

Author emphasis on electric motors and how do they work. He mentioned that main difference between 3 phase induction motor and the DC brushless motor is their rotor.

main points are,

• There is no such thing called the best engine. According to the personal requirements, we need to adapt the engine type.
• In the course of time, Lead-acid batteries are replaced by Lithium-ion batteries.
• In the course of time, DC brush motors are replaced by DC Brushless or Induction Motors.
• In the course of time, Contactor Controllers are replaced by Modulating Inverters.
• There is a bigger concern regarding the stable use of these elements mentioned above over the next few decades.
• The author discusses the two technologies such as: 1. DC Brushless Drives and 2. Induction Motor with it's feature of operation.
• He says brushless motors are useless motors without the inverter.
• He also mentioned that the 3-phase induction motor has great utility but with several limitations.
• The major limitation being, the Induction Motor can not operate from DC, and AC is a must.
• Further, he compares the future trends which may occur in DC Brushless as well as in Induction motor.

colclusion:

When it comes to hybrid or plug in hybrid vehicle market dc brushless motor will dominate. However, Induction motor drive will always dominate for high performance and pure electrics. So, author have not mentioned who is clear winner among two rather he emphasis on advantage and disadvantages of one drive over another.