Week-6 Challenge: EV Drivetrain

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

A . 1. Types of power converter circuits employed in eletric and hybrid electric vechicle

. DC-DC converter

. DC-AC inverter

. AC-DC rectifier

DC-DC converter ; DC-DC converter can be used to interface the elements in the electric power trian by boosting or chopping the voltage levels .By introdution DC/DC converters one can choses the voltage variation of the deveices and be controlled .

The amount configuration of ev power supply show that at least one DC/DC convereter is necessary to interface the battery or the supercapaitors module to Dc-link

The amount of power flow between the input and the output and the output can be controlled by adjusting the duty cycle.

DC-AC Inverter; Converts direct current DC from the battery to alternating current Ac to be used devices such as th traction motor and conterd pump

AC -DC rectifier; Eletrical cars have batteries that run on direct current power

so the AC power which we use for charging batteries is coverted to DC using a rectifier which feeds Dc power to the Battery .

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'.

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 duty cycle is 70%?

A. Givenm ;

motor and controller paramerters;

rated armature voltage =72v

rated armature current=400A

Ra= 0.5Ω, KΦ= 0.7 Volt second

Chopper Switching frequency= 400 Hz

Duty cycle =70% V bat = 72v

we know that

Ω=Vt/KΦ-Ra/KΦ^2.(Tt)

Vt = Vbat *Duty cycle

=72*0.70

=50.4

Ω=(50.4/0.7)-(0.5/(0.7)2).(Tt)

Tt= (72-Ω)/1.020

Tt= 70.58-0.98Ω

But we know that

Tv = 24.7 +0.0051Ω^2

comparing Tv and Tt

24.7 +0.0051Ω^2=70.58-0.98Ω

0.0051Ω^2+0.98Ω-45.88=0

(Ω-38.92)(Ω+231.08)=0

Ω=38.92-231.08

speed cannot be a negative hence consider only the postive value

so therefore Ev steady state speed = 38.92rad/sec

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

ω">ωω= V/Kϕ">ϕϕ -Ra/Kϕ">ϕϕ^2

A. Why to model mathematically; Mathematical modeling is one of the bases of conversion activity of a real problem in a mathematical form and this modeling involves to formulate the real- life situations or to convert the problems in mathematical explanations to a real or believable situation.

Adove eqution can be implemented using the simulinkk model as follows:

Contant block;

4 Refer to the blog on below topic:

Induction Versus DC brushless motors by Wally Rippel, Tesla

Explain in brief about author’s perspective.

A. All engines are alike and it to the user to select one according to his/her requirements. Due to the improvising technology,

There has been alternatives found now and then such as lead-acid batteries, DC brush motors and contact controllers have been replaced by lithium batteries, brushless DC or induction motors and inverters.

1. Though there has been various replacements, brushless DC and induction motors are playing a major role till this date. 2 . The construction and working of thebrushless motors and induction motors are being discussed. the stators for the 3-phase.

Induction motor and the DC brushless motor are virtually identical. Both have three sets of "distributed windings" that are inserted within the stator core. Both drives use 3-phase modulating inverters. The only differences are the rotors and the inverter controls.

3. The pros and cons of both brushles DC motors and induction motors are being discussed. The advantages of brushless dc

motors are: much less rotor heat is generated. the peak point efficiency will only be a few % higher than an induction motor. The

disadvantages are: as the machine size grows, the magnetic losses increase proportionately and part load efficiency drops. permanent magnet (PM) rotors are also difficult to handle due to very large forces that come into play when anything feromagnetic control them.

4. Induction motor has some advantages: the motor has no magnets. The motor can start under no-load conditions. the

disadvantages are: they cannot operate in DC. When operated with utility power, they have limited starting torque and limited and limited running peak trouqe capabilities when compared to DC type of machine s

5. The author's conclusion is that DC brushless drives will likely continue to dominate in the hybrid and coming plug-in hybrid markets and that induction drives likely maintain dominance for the high -perfromce pure electrics

conclusions ;

1 ; The types of power convertion cricuits employed in an electric and in the hybrid electric vehicle were studied.

2 . An Electric vehicle powertrain with 72v batter pack in shown in the diagram below .the duty ratio for ratio acceration operation is d1 and for the braking operation the duty ratio is d2.rated armature voltage =72v .rated armature current =400v .Ra=0.5Ω KΦ=0.7volt second .chopper switching frequency=400Hz. vechicle speed torque characteristicsTv=24.7+(0.0051)w with which the Evsteady speed if duty cyclye is 70% was calculated.

3 .A mathematical model of dc motor for the below equation using simulink was developed.

ω">ωω= V/Kϕ">ϕϕ -Ra/Kϕ">ϕϕ^2 .T