Week-6 Challenge: EV Drivetrain
1) In the electric and hybrid electric vehicle the power electronics converter are considered, in order to design a highly efficient converter for the EV power system advanced dc/dc converter and dc /ac converter is required
commonly used power converter
Ac to Dc CONVERTER are commonly used in plug-in hybrid electric vehicles and plug-in electric vehicle
these vehicles get their propulsion power from an external electricity source which is alternating current . The battery needs to be charged using a direct current source. for this purpose Ac to dc converter used
DC-DC CONVERTER
Dc to Dc converter can be used to interface the element in the electric power train by boosting or chopping the voltage levels
The power of the dc /dc converter depends on the characteristic of the vehicle such s top speed, acceleration time from 0 to 100km/h, weight, maximum torque, and power profile
DC TO AC CONVERTER
This converter is used to dc power to a suitable ac power for the electrical machine. the power output from the battery pack (dc current) is converted using an inverter to be used in an electric motor (Ac current)
2)
given data
Rated armature voltage=72v
rated current = 400A
Ra=0.5ohm k(PHY)=0.7 volt second
Duty cycle=70%=0.7
actual voltage= 0.7*72=50.4 v
we have torque equation
T=Vkϕ/Ra−((kϕ)2/Ra)⋅ω
(50.4.0.7)/0.5-((0.7)^2)/0.5.w
T=70.56-0.98.w ----- eqn 1
T(v)=24.7+(0.0051)w^2 ----- eqn 2 ( given)
comparing both equations
comparing both torque of vehicle and torque of motor
24.7+(0.0051).w^2=70.56(0.98).w
0.0051w^2+0.98^w-45.86=0
by solving this quadratic equation we get two w value
w=38.915rad/sec and w=-231.072 rad/sec
so the EV steady state speed if duty cyle is 70%=38.915rad/sec
or 371 rpm
3)
4)
he explains the working of both 3 phase induction motor and brushless dc motor and a brushless Dc motor
The author has done a comparison between these two technologies and stated some advantages and disadvantages each
induction motor has some advantages, it has no magnet. 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, and shaft speed is proportionate to line frequency. hence when used with utility power they are constant utility power. when operated from utility power they have limited starting torque and somewhat limited running peak torque capability when compared to dc type machines.
brushless dc motor has some advantage like much less rotor heat generated with the dc brushless drive
some disadvantages of brushless dc motors are as the machine size grows magnetic loses increases proportionately and part load efficiency drop permanent magnetic loss increases proportionately and part load efficiency drop