Week-6 Challenge: EV Drivetrain

                   EV LIVE BATCH - 16

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

      ω">ωω=   V/Kϕ">ϕϕ -Ra/Kϕ">ϕϕ^2    .T?

SOLUTION:

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%?

SOLUTION :

GIVEN DATA:

Rated aramature current= 400A

Rated aramuture voltage =72v

Ra=0.5ohm

Chopper Switching frequency= 400 Hz

KΦ= 0.7 Volt second

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

          

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

Rated aramature current= 400A

Rated aramuture voltage =72v

Ra=0.5ohm

Chopper Switching frequency= 400 Hz

KΦ= 0.7 Volt second

Duty cycle (DC)=70percentage =0.7

The average voltage is given by the product of the batttery voltage and the duty cycle,

vs=v*dc

vs=72*0.7

vs=50.4

THE AVERAGE VOLTAGE IS 50.4V

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

          

The derived formula for the motor speed in the form of the equation:

T= vs*KΦ\Ra -((KΦ)2*w\ra))

By substituting the values,

50.4*0.7\0.5 -((0.7)2*w\0.5)

T=70.56-0.98

compare the equations 1 & 2,we get

70.56-0.98=24.7+(0.0051)w2

0.0051.w2+0.98w-45.86=0

By using the quadrant equation formula we get,

w=-0.98+- 1.377\0.0102

we get the solution for this angular speed,

w=38.92rad\sec

w=-231.07rad\sec

we can consider only +ve value,

Angular speed=38.92rad\sec...

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

SOLUTION:

power converter circuits are employed in electric and hybrid electric vehicle:

• power converts are electrical and electronics circuits that are used to either connect DC to AC and vice versa 
• In the simpler words, as we know that power converters are circuits which are used to convert one level of voltage into other in terms of its nature (DC to Ac) and also in terms of its level so as to increase so as to increase or decrease its level (DC to AC) and also in terms of its level so as to increase or decrease its level ( DC to DC ,AC to AC converters)

AC TO DC CONVERTER OR RECTIFIER (EV CHARGER);

• AC to to Dc converter are one of the most important in power electronics because there are lot of real applications are based on this conversions.
• our homes at a voltage of 230v at frequency of 50hz which we can use to power generated from a powerplant is transmitted to our electrical applicances

RECTIFIERS CAN BE CLASSIFIED AS;

1) HALF -WAVE AND FULL -WAVE RECTIFIER

2)CONTROLLED AND UNCONTROLLED RECTIFIER

3)CENTER -TAPPED AND BRIDGE RECTIFIER

Also ,based on the input supply(Ac) ,rectifier can be of single phase and three phase also.

Uncontrolled converter converts fixed DC voltage ,it mean the value of output for a given value of input AC voltage.

DC TO DC CONVERTER :

• DC to DC converter in an electric vehicle may be classified into unidirectional and bidirectional converters.
• unidirectional DC to DC converters to various onboard loads such as sensors ,control,safety equipments,etc
• the chopper or DC to DC converter topologies are classified as"
• BUCK CONVERTER
• BOOST CONVERTER
• BUCK -BOOST CONVERTER

BUCK -BOOST CONVERTER

• The output voltage can be either higher or lower than the input voltage 
• THe average output voltage is given by,
• Vo=(DVs)\(1-D)\
• D can be varied from 0 to 1
• when D=0.5
• vo=vs
• when ,vo=infinity
• Hence,in the internal 0<=D<=0.5,the output varies in the range 0<=vo<=vs
• we get step down or buck operation
• interval 0.5<=D<=1
• vs<=vo<=infinity

DC TO AC CONVERTER (INVERTER):

• A DC to AC converter or an inverter is a device that converts DC power from the battery to AC power used in an electric vehicle motor
• the inverter can change the speed at which the motor rotates by adjusting the frequency of the alternating current
• AC TO DC CONVERTER (RECTIFIER)  is used in EV charger
• DC TO DC CONVERTER(CHOPPER) is used to supply DC power to Auxiliary like radio and car headlights
• DC TO AC CONVERTER(INVERTER) is used to supply power to motor.

BUCK CONVERTER:

• the buck converter is also known as step down converter and product a lower output voltage than the Dc input voltage
• this voltage is allowed to charge the load and power the load through the diode when the switch is off, maintaining current output throughtout the switching cycle.

THE AVERAGE OUTPUT VOLTAGE IS GIVEN BY,

Vo=(TOn\T)*VS=DVs

BOOST CONVERTER;

• the output voltage is always greater than the input voltage
• the working of boost converter can be explained here.the input voltage source is connected to an inductor

THE AVERAGE OUTPUT VOLTAGE IS GIVEN BY:

VO=(VS)\(1-D)