Week-6 Challenge: EV Drivetrain
1.
Types of power converter circuits are used in electric and hybrid electric vehicle are:-
These are the electrical circuits helps in transforming on form of electrical eneryg to anothor form. The converter that helps in increasing the voltage called step up converters like wise the converter that decrease the voltage called step down converter.
The power electronic components are made of up high power fastacting semi conductor materials like BJT(Bi polar junction transistor) , MOSFET , TRAIC, SCR etc.
Here in EV & HEV these converters plays an important role as in this the power requirement is high for the durability , efficiency, high torque production in the vehicles .
Their are different types of converter:-
1. AC to AC converter (voltage regulator)
Here our input is AC and output is also AC so what is convert is it increase the voltage level simontaniously by increasing the frequency of the signal. These are used in various systems like renewable energy conversion , aircraft converter system etc.
It has some application like electric machine control ,stroage sysytem, power generation and distribution , embedded technology.
Output will be sinosoidal in nature.
2. AC to DC converter(rectifier)
It is also called a rectifier as it converts a AC voltage signal to DC signal.After conversion o it gives a pulsating DC signal which later passed through the filter circuit.Hence we get a proper DC signal.
Mobile charger as the most common example of AC-DC converter.
Output will be a constant value.
3.DC to DC converter (chopper)
DC -DC converter are basically used for converting a high level DC singal to low or vice versa.In electric vehicle and hybrid vehicle this plays a important role.
In electric vehicle there are two types of power system like one of high voltage for traction and a low voltage for the vehicle accessories like speedometer light , ignition light etc.
It leads to bidirectional flow.
Output will be a constant value.
4.DC to AC converter(invertor)
A DC-AC converter is a device which convert a DC signal to AC signal .By using this converter we can increase or decrease the power and torque by varying amplitude as here a frequency generates.
It plays a vital role in regenerative breaking.
It has a direct impact on on road perfermance and relability.
Output will be sinosoidal.
Therefore,these are some power converter used over EV and HEV for various purposes .
2.
An Electric Vehicle's powertrain with 72V battery pack is given.
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
Kphi= 0.7 Volt second
Chopper Switching frequency= 400 Hz
The vehicle speed-torque characteristics are given by the below equation
Duty cycle is increased by 70 %.
Output voltage from chopper = 72*70/100=72*0.7=50.4
Torque - speed char. equation = (v - w*kphi)*kphi/Ra
= (50.4 - w*0.7)*0.7/0.5
=70.556 - 0.98w
Computing above equation with tha main equation given = 70.56 - 0.98w = 24.7+(0.0051)*w^2
=0.0051*w^2 + 0.98*w - 45.86 =0
Solving above equation we get that w = 38.86 rad/s
Therefore, the steady state speed of EV while duty cycle 70% is w = 38.86 rad/s
3.
Mathematical model of a DC Motor for speed torque characterstics using simulink.
Here we have taken all the previous value mentioned like
Ra= 0.5
V = 220v
kphi = 0.7
So,simulaton is done using some constant block , product block , a ramp block for torque and scope to view the result.
Angular Speed - torque Equation:
w = v/kphi - Ra/(kphi)^2 * T
Hence , output and simulations are uploaded below.
4.
>Here the author Walley Rippel gives a clarity about the difference between induction motor and DC brushless motor in both electric and hybride electric vehicle. This blog is published in TESLA official website and he is a long time proponent of electric vehicles. At the beginning of his journey he started working in general motor for the first electric vehicle (EV1) .
>In this the author described some positive and negative side of both the motor and some constructions about it .
>DC brushless motor have some permanent magnet which induces a rotating magnetic field and this produces a current in the conductor . This results a generation a force which starts rotor moving.
=>It generates less heat.
=>It will not produce starting torque at some cases.
=>paramnent magnet needed.
=>It can operate in unity power factor.
=> Easily controllable than induction motor.
=>Rotor colling is easier.
>While in induction motor it dont have magnets ,here the current is supplied to the stater which produces in generation of emf as stator rotor are acting wisely so in rotor a current will also generated which make rotor rotate .
=>For the operation of this motor AC must be needed.
=>It can operate at 85% of power factor.
=>Torque is low when compared to DC motor.
=>No magnets needed.
=>At low load it gives higher efficiency.
>Motor with brushless produces torque and motor of induction can produce minimum torque and desired torque too.
>Both have some similarities like stator and 3-phase modulating inverter. Mostly is the difference about rotor and inverter control of system.
>The construction of DC brushless motor is might be costly as here permagent magnets are used while not in induction machine.
>Speed variation is difficult to control in induction machine.
>Author here trying to solve the problems found by those motors and simontaniously doing resreach about its future uses.