Week-6 Challenge: EV Drivetrain
TASK 1.
AIM:
To get to know the types of converters used in HEV and EV vehicles.
OBJECTIVE:
To get information on converters for HEV and EV vehicles.
THEORY:
In electric and hybrid vehicle,power electronic is responsible for converting and controlling electric power in system.Some of the major power electronic components and functionalities are used in electric vehicle system.These include inverter,converter and on board charger.Operations at high voltage or high current can be efficiently exexuted by utilizing power electronic devices,as they deriver faster switching rate at higher efficiency in addition,power electronics control both unidirectional as well as bidirectional flow of energy,depending on the usage,and the regenerated energy can be sent back to utility.
THE THREE TYPES OF CONVERTER USED IN ELECTRIC VEHICLE ARE:
AC-DC CONVERTER:-
Ac to dc converters are most commonly used in plug in hybrid electric vehicles(PHEV) & plug in electric vehicles(PEV).These vehicles get their propolusion power from an external electricity source (charging stations) which is alternating cuurent.The battery needs to be charged using a direct current source.For this purpose,AC to DC converter is employed in a PHEV & PEV.
DC-DC CONVERTER:-
A DC to DC converter is a category of power converter and it is an electric circuit which converts a source of direct current(DC) from one voltage level to another,by storing the input energy temporarily and then releasing that energy to the output at a different voltage.The storage may be in either magnetic field storage componwnts ( inductors,transformers) or electric field storage components (capacitors).
DC TO DC converters can be designed to transfer power in only one direction,from the input to output.However,almost all dc to dc converter topologies can be made bi-directional.A bidirectional converter can move power in either direction,which is useful in applications requiring regenerative braking.
DC-AC CONVERTER:-
An inverter is a device that convertes DC power to the AC power used in an electric motor.The inverter can charge the speed at which the motor rotates by adjusting the frequency of the alternating current.It csn also increase or decrease the power or torque of the motor by adjusting the amplitute of the signal.
TASK 2.
AIM:
To find the speed using torque- speed relation.
OBJECTIVE:
Find the speed using torque speed relation.
SOLUTION:
GIVEN INPUT
Battery pack voltage(V)=72 V
Rated armature current=400 A
Armature resistance (Ra)=0.50
Motor constant (kΦ)=0.7
Chopper switching frequency=400 HZ
Duty cycle=70%
`v=24.7+(0.0051)w2......eq 1
Vehicle output voltage (V) * duty cycle
V=72*0.70
Thus,vehicle voltage=50.4V
now,torqu equation for motor,
T`=VKΦ/Ra-((k'Φ')^2/Ra)*ω
T= 50.4*0.7/0.5-((0.7)2/0.5)*ω
T=70.56-0.98ω ........eq. 2
solving eq.(1)&(2),
Comparing both torque of vehicle and torque of motor,
24.7+(0.0051)*ω^2=70.56-(0.98)*ω
0.0051ω2+0.98ω -45.86=0
by solving this by quadratic eq. we get
we get 2 values of ω as
ω = 38.915 rad/sec
and
ω = -231.072 rad/sec
so, the EV steady state speed if duty cycle is 70%=38.315 rad/sec
TASK 3.
Given data
ω =V/KΦ-Ra/KΦ^2.T
The basic blocks which are required for carrying out the plotting of a function in simulink.
1.CONSTANT BLOCK
2.SQUARE BLOCK
3.MULTIPLICATION
4.DIVIDE
5.ADD BLOCK
6.DISPLAY
TASK 4.
AIM:
To get to know about induction and DC brushless motors.
OBJECTIVE:
Try to find the best options for motors for HEV or EV vehicles.
EXPLANATION:
His prospective about electric vehicle future technology cannot be predicated easily.The gas powered vehicles engines are not all same and there is no best engines are not all same and there is no best engine type people choose according to their requirements such as price and performance these also comes under electric vehilces but in nearly future EV drives may get stability.
The author said that both induction motor and DC brushless motor have advantages as well as disadvantages and he explained about basic construction of both the motors.
Induction motor does not have permanent magnets and it is connected to three phase utility power,torque is produced at the outset the motor has ability to start under load so the inverter is not needed so it has ability to compatible with the conventional vehicles.If induction motor size increase the losses will not increase.With the help of induction motor drive we can achieve required high performance.Limitations of induction motor is it requires source power as AC it will not operate in DC.This motor has limited starting torque and limited running peak torque capabilities as shaft speed is proportionate to line frequency so in order to overcome such draw backs it requires an inverter and feedback signal and speed variation depends upon the frequency input.It is hard to control.
In DC brushless motors the strength of magnetic field is adjusted when maximum torque is required,especially at low speeds,the magnetic filed strength should be maximum so that inverter and motor currents are maintained at their lowest possible values.This minimizes the l2R losses.Where DC brushless machines requires permanent magnets which is cost efficient.Construction of DC brushless motor costly compared to induction motor because pf magnets.
He finally said that DC brushless motors will ddominance in HEV and PHEV and induction motor is highly preferred in pure EV.