Week-6 Challenge: EV Drivetrain
Power converters:
Electric and hybrid electric vehicle, power converter is interface their power source to the drive train of the EV's in order to design highly efficient converters of the power system, advanced DC/DC and DC/AC converters are required to adopt the output voltage and current level
Types:
- AC/DC converter
- DC/DC Converter
- DC/AC Converter
AC/DC converters:
- Also called as rectifier
- Transform AC input to DC output
- It also converts AC voltage to variable DC voltage
- Used in PHEV and PEV
DC/DC Converters:
- Also called as chopper
- Converts a source of DC from one voltage level to another .
DC/AC converter:
- Also called as inverters
- Converts DC input to AC output
- It rely on traitor, capacitor, transistor, and other circuit devices for converting DC voltage to AC voltage.
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:
Duty cycle=70%
Actual voltage=72*0.7=50.4V
The Speed of the motor equation
ω=v/kΦ -[(Ra/(KΦ)^2).T]
the above euation change the toque
T=[VKΦ/Ra]-[ω(kΦ)^2/Ra]
=72*0.7/0.5-ω(0.7)^2/0.5
=35.28-0.49ω/0.5
T=70.56-0.98ω---------2
TV=24.7+(0.005)ω^2----------1
from equation 1 and 2
70.58-0.98ω=24.7+(0.0051)ω^2
-0.98ω=24.7+(0.005)ω^2-70.56
-0.98ω=0.051ω^2-45.86
0.0051ω^2+0.98ω-45.86=0-----------3
quadratic form
ω1=38.912rad/secω2=-231.068rad/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 .T
Voltage=50.4V
kΦ=0.7
Ra=0.5ohm
torque is ramp signal
4.Wally Rippel’s perspectives are
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has been alternatives found now and then such as lead-acid batteries, DC brush motors and contact controllers have been replaced by lithium batteries, brushless DC or induction motors and inverters.
Though there has been various replacements,
Brushless DC and induction motors are playing a major role till this date.
The construction and working of the brushless 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.
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.
Disadvantage:
- The machine size grows
- The magnetic losses increase proportionately and part load efficiency d
- Permanent magnet (PM) rotors are also difficult to handle due to very large forces that come into play when anything ferromagnetic gets close to them
- Induction motor has some advantages:
- The motor has no magnets.
- The motor can start under no-load conditions.
Disadvantages:
- They cannot operate in DC.
- When operated with utility power
- They have limited starting torque and limited running peak torque capabilities when compared to DC type machines.
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 will likely maintain dominance for the high-performance pure electrics.
DC Brushless Induction Motor
Absolute Position Sensor Absolute Position Sensor
Operate Unity Power factor Power Factor is 85%
Peak Point Efficiency Higher Peak Point Efficiency Higher
Average Efficiency is Low Average Efficiency is High
Permanent Magneta are Expensive No Magnet
Easy To Control Control is Complicated
EV BATCH17