Week-6 Challenge: EV Drivetrain
1. Power Converter Bascically Used the converter electrical Power From one form to another form (AC_DC And DC_AC) Some time change the Level of the power Change the voltage Stepup and stepdown
!_ Electrical Vehicle -
As per above picture bascically we used the We used three typr of power converter in the Electrical Vehicle DC_DC,AC_DC,DC_AC
AC_DC - This Converter bascially called as Rectifier .This converter we used in the EV in The On Borad Charger we take AC supply from the Grid and we need to coverte this supply to DC for the battery charging so that time we used the AC-DC Converter for the Charging the battery .
DC-DC - This Converter Bascially called as Chopper .This Converter we used in EV for the Main HV battery to the LV Aux Battery for that we used BUCK Converter so it will step down the voltage . Buck Converter we used in the EV For the Aux Load in EV like Head Light and Head Lamp etc and another one is Boost Converter we used for the Setp up the DC Supply .
DC-AC - This Converter Bascially called as Inverter .This Converter we used in EV when we used AC motor in EV that time we need the DC-AC Converter .we take the supply from the Battery and given to the motor so battery power is DC for AC motor we need the AC power for the we used the Inverter.
@- HEV-
Power Converter Bascically Used the converter electrical Power From one form to another form (AC_DC And DC_AC) Some time change the Level of the power Change the voltage Stepup and stepdown
AC_DC - This Converter bascially called as Rectifier .This converter we used in the HEV when the Engine connected with the generator and genrate the AC Supply that Time we used the Rectifier for the Converter into DC supply.
DC-DC - This Converter Bascially called as Chopper .This Converter we used in HEV for the Main HV battery to the LV Aux Battery for that we used BUCK Converter so it will step down the voltage.Aslo when suupply come from the genrator we have to the charge HV battery for that time we need Boost converter.
DC-AC - This Converter Bascially called as Inverter .This Converter we used in HEV when we used AC motor in HEV that time we need the DC-AC Converter .we take the supply from the Battery and given to the motor so battery power is DC for AC motor we need the AC power for the we used the Inverter.
2.
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%
W= 38.92 Rad/sec
3.
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
Spped Toruqe Graph
4.
Refer to the blog on below topic:
Induction Versus DC brushless motors by Wally Rippel, Tesla
Explain in brief about author’s perspective.
The author writes this blog to entail the differences between the two most commonly used motor drives in the automobile industry: the DC brushless motor drive and the induction motor drive. Rippel goes in to detail about the differences in construction, working, and cost between the two drive types. However, with what he has written, he has not arrived at the conclusion that one type is better than the other. In the last lines of the opening paragraph, Rippel writes that \"there is no one best engine type\" and that it is all a matter of personal preference when it comes to choosing an engine. It is in this same regard that he ends the blog stating that there is still \'no winner\' when it comes to motor drive selection either. In spite of both motor drive types having similarities, they also have their benefits and drawbacks.
For DC Brushless drives, we are told that their construction implements 2 or more permanent magnets at the rotor to generate a DC magnetic field. It also consists of a stator core (made up of thin, stacked laminations) It also uses an inverter for the current control, meaning that it cannot run on a DC power supply as the current direction has to be changed repeatedly in to maintain a constant torque.
For induction drives, there rotor has no magnets, but instead stacked steel laminations with buried peripheral conductors which form a \'shorted structure\'. It is the current in the stator windings that generates a rotating magnetic field that interacts with the rotor.
Induction motors can be used directly with power from the mains and does not require an inverter to start the drive and generate the starting torque. It has the ability to start under the mains load applied. However, DC brushless drives cannot do the same. They cannot generate a starting torque when connected to a mains power supply. They require an inverter to do this.
Induction motor drives cannot run on a DC power supply and are solely dependent on an AC power supply. Also, when they are connected to a 3 phase mains supply, the rotor rotates at a constant speed and also they have a limited starting torque as well as peak torque. In order to rectify this, an inverter can be used to operate the induction drive from a DC power supply or a battery. Also, if the inverter frequency is varied, then the constant speed is no longer an issue - it can be varied.
DC Brushless drives use permanent magnets, and cannot change the strength of their magnetic fields. It would be desirable if they could, because when the maximum torque is needed by the rotor, the magnetic field strength should also be at a maximum level. This allows for the inverter and motor currents to be at a minimum, thereby reducing the power loss by heat dissipation. Similarly, when the torque required is minimum, the magnetic field strength should also be minimum to reduce hysteresis and eddy current losses. The permanent magnets used are also quite expensive costing $50 per kilogram and their magnetic fields are difficult to control if ferromagnetic material gets close enough to the field.
On the other hand, induction drives do not have permanent magnets and so they can vary their magnetic field strength. If used with a smart inverter, they can be operated with minimum hysteresis and eddy current losses and maximum efficiency as the magnetic field strength can be changed according to the requirement by the rotor. These losses do not increase if the size of the induction drive also increases but as a DC brushless drive gets bigger, its losses increase and their efficiency decreases. So induction drives have a cost advantage compared to DC brushless drives
Although, DC Brushless drives generate less heat at the rotors. So rotors more easily and have a higher peak point efficiency than induction drives. In addition, the DC brushless motor can operate at unity power factor i.e. 1, whereas induction drives can operate up to a power factor of approximately 85%.
In conclusion, Rippel has elaborated the different aspects to compare the induction and DC brushless motor drives and has detailed the advantages and disadvantages of both types. As mentioned earlier, at the end of the day it depends on the preference of the user. If a user is seeking a high performance with comparatively lesser costs, then the induction drive would be better suited for those requirements. However, if it is high peak point efficiency, high power factor and easier control that a user seeks, then the DC brushless drive would be the smarter choice. Both types have their place in the automobile industry and will retain their relevance in their respective applications. Rippel believes that due to the increasing performance of vehicles, one day both may be used side by side under the hood of a vehicle in order to get the best of both drives. This would result in a new kind of hybrid that combines the characteristics of an ordinary vehicle e.g. sedan with that of a sports car.