Week-6 Challenge: EV Drivetrain

ANSWER 1.

We can distinguish four categories of converters, based on source input voltage and output voltage.

• AC to DC converter (rectifier): This inverter converts the AC supply to a DC supply for the load, or in other words, the inverter turns an AC voltage into a DC voltage.
• DC to AC converter (inverter): DC to AC converters are devices that convert DC input voltage to AC output voltage. The output voltage of the inverter can be a variable or fixed AC voltage with variable or fixed frequency.
• AC to AC frequency converter (transfarmer): AC to AC converters are mainly used to convert the frequency of the input voltage/current from the source to desired load level.
• DC to DC voltage (Chopper): DC to DC converters are devices that convert a DC input voltage to a desired DC output voltage level. This type of converter consists of power electronic switching devices, such as thyristors, connected in such a way that they supply the required DC voltage to the load.

ANSWER 2.

Given Parameters:
Rated Armature voltage= 72 V
Rated armature current= 400 A
Ra= 0.5Ω and KΦ= 0.7 Volt second
Chopper Switching frequency= 400 Hz

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

Tv=24.7+(0.0051)ω^2................equation(1)

solution:

Duty cycle=70%=0.7,

Actual voltage=0.7*72=50.4V

We have torque equation for motor,

T=[(V*kϕ/Ra)−((kϕ)^2/Ra)*ω]

T=[(50.4*0.70/0.5)−((0.7)^20/0.5)⋅ω]

T=70.56−0.98ω.......................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,

we get two ωvalues as

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

ANSWER 4.

The following points can be concluded from the above topic:

• In the very starting, author explains the dominance of the ICE in the world of automobile industry and also discuss different types of engines.
• Then he also explain about induction motor and brushless DC motors and presents his view that these two technologies will be widely used for the coming years.
• After that he describes the working of both 3-phase induction motor and a brushless DC motor.
• After that author explain the advantage and disadvantage of INDUCTION MOTOR and DC MOTOR.

Advantage of Induction motor are:

• It has no magnets.
• The motor has the ability to start under load.
• No inverter is needed.

Some disadvantages of Induction motors are:

• They cannot operate from DC
• AC is a must for this.
  
  

Advantage of DC Motor are:

• There are less rotor heat is generated with the DC brushless drive.
• The peak point energy efficiency for a DC brushless drive will typically be a few percentage points higher than for an induction drive.

Some disadvantages of Brushless DC motor are:

• As machine size grows, the magnetic losses increase proportionately and part load efficiency drops. Permanent magnets are expensive and difficult to handle due to very large forces that come into play when anything ferromagnetic gets close to them.
  

Finally he concluded 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.