Week-6 Challenge: EV Drivetrain

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

Power converters are used in motor controllers to control vlotage and frequency and generally used to convert power flow from one form to another form.

The power electronic circuit consists of the both the power part and the control part.

The power part transfers the enegry from source to load and it consists of power electronic switches,transformers,electric choke,capacitors.

The power converters can be mainly classified as

1. AC TO DC converters
2. DC TO AC converters
3. DC TO DC converters
4. AC TO AC converters

1.AC to DC converters:

This conveter is also known as rectifier. A rectifier is an electrical device comprised of one or mopre diodes that allow the flow of current only in one direction it converts AC supply from the main lines to DC supply.

Rectifiers are mainly two types they are

1. Uncontrolled diode rectifiers
2. controlled rectifiers

2.DC TO AC converters:

This conveter is also known as inverter. A power inverter is a power electronic device or cicuitry that changes direct current(DC) to alternating current(AC) the input the inverter can be entirely electronic or maybe a combination of mechanical effects and electronic cicuitry

Inverters are mainly two types they are

1. PWM based inverters
2. Multilevel inverters

3.DC TO DC converters:

This conveter is also known as chopper A chopper is basicallt a DC TO DC converter whose main function is to create adjustable DC voltage from fixed DC voltage sources through the use of semiconductors. These can be unidirectional or bidirectional devices based on the application it is intended for.

choppers are classified intlo three types

1. Step-down or buck converter
2. Step-up chopper or booster converter
3. Buck or booster converter

4.AC TO AC converters:

This conveter is also known as cycloconverter or matrix converter. cycloconverter converts a constant voltage,constant frequency AC wave from to another AC wave form of different frequency. a cycloconverter achieves this by synthesizing the output wvaeform from segments of the AC supply

There are two types of converter they are

1. AC to AC voltage converters
2. AC to AC frequency conerters

2.

Given

Rated armature voltage=72V

Rated armature current =400A

Ra=0.5

chopping switching frequency=400Hz

The vehicle speed torque characteristics are given in a equation that is

Tv=24.7+(0.0051)w^2

Torque speed charactersistic of DC motor is

T=(V.K/R)-(K^2.W/R)

Where

T=Torque

V=Armarture voltage

R=Resistance

W=Speed

by equating the two equations we get

24.7+0.0051*W^2=(V.K/R)-(K^2.W/R)

24.7+0.0051*W^2=((72*0.7*0.7)/0.5)-(0.7*0.7/5)*W

24.7+0.0051*W^2=70.56-0.98*W

W^2+192.15*W-8992.15=0

BY solving the roots we get one postive and one negitive value

speed cannot be negitive so

W=38.9rad/sec.

EV steady state speed if duty cycle is 70% is 38.9rad/sec.

4. Induction versus DC brushless motoers by wally rippel

In this he explains how induction brushless motor used now a days.

1. The electric drive vehicles are various types based on the usage,price and performance
2. Previouslt lead acid batteries and DC brush motors and contactor controllers are use now they are replaced by lithium batteries and DC brushless motors are used
3. Motors are useless without the inverter
4. Induction motor is invented by nikola tesla and both motors contain same type of stators which contains three sets of distribyted windings
5. rotor doesnot have magnets they have stacked stell laminations with buried peripheral conductors which forms a small structure
6. When the induction motors are used there is no need of inverter induction motoers are directly capable with conventional utility power
7. Inverters are used in DC brushledd motors to develop torque
8. variable speeds also become possible simply by adjusting the inverter frequency
9. This shows the induction motors are competant with DC motor
10. Most of the vehicles now a days have DC brushless motors only some vehicles li tesla roadster and gm ev1 have induction motors
11. And also about permanent and ferromagnets used in EV and cost and forces they gain in motors
12. laws are more to contorl the induction motors so it is difficult
13. DC motors have more dominance in hybrid and plug hybrid vehicles where induction motors have dominance in pure EV .