Week-6 Challenge: EV Drivetrain
Question:1
Aim: To find Which types of power converter circuits are employed in electric and hybrid electric vehicle?
Answer: What is power electronics?
Power electronics is about that deals with the process of high voltages and currents to deliver power that supports a variety of needs. Power supply in one form is processed using power semiconductor switches and control mechanisms to another form by supplying a regulated and controlled power.
When switched mode power supplies are a common application of power electronics where power density reliability and efficiency are of prime importance objectives.
About the power electronic converters: Power electronic converters play the major role of taking electrical energy from the power system and turning it into a suitable form needed by a motor. The power electronic converter may be described according to the given power source and the driving motor.
Various types of power electronic converters:-
They are mainly classified into 4 types they are,
- AC to DC Converter (Controlled Rectifier)
- DC to DC Converter (DC Chopper)
- AC to AC Converter (AC voltage regulator)
- DC to AC Converter (Inverter)
1) AC-DC converters: This type of converters are aslo called as the rectifiers,they mainly convert AC to DC,then use it through a filter to obtain an unregulated DC voltage.
Example of Ac to DC converter circuit
Again this AC-DC converter is divided into two types they are 1) Full wave rectifier and2) half wave rectifier
AC-DC converters can have more than one output and may feature overcurrent, overvoltage, or short circuit protection.
Applications:AC-DC converters are used in computers televisions cell phone chargers and other electronic devices. They are also used in medical military and telecommunications equipment kitchen appliances; industrial machinery and commercial products that use DC motors.
2) DC-DC converters: This type of converters are aslo called as the choppers,they mainly converts fixed dc into variable dc. DC to DC converters uses a method to increase voltage from a lowered battery voltage thereby saving space instead of using multiple batteries to the same thing. Most of the DC-to-DC converter circuits also regulate the output voltage.
The DC-DC converter work as high-frequency power conversion circuits that use high-frequency switching and inductors transformers and capacitors to smooth out switching noise into regulated DC voltages. Closed feedback loops maintain constant voltage output even when changing input voltages and output currents
It is aslo called as also called step-down DC-DC converterit is a DC-DC power converter which lowers the output voltage, when its increasing the output current.
3) DC- AC converter: This type of converters are aslo called as the inverter,they mainly converts Dc to AC of desired frequency and voltage.
It is easy to convert AC to DC all you need to do is to feed the current through a diode which only passes current in one direction.But Converting from DC to AC is more complicated because you need some kind of oscillator that reverses the current direction at the frequency you need. There is a way to do this mechanically but most inverters depends on resistors capacitors transistors and other circuit devices.
And also inverter needs one more thing the way to alter the voltage of the current source for use by the device that will be using the power. In other words it needs a transformer.
For example, if you are powering your 130 V refrigerator with a 13 V battery, the inverter needs a step-up transformer that increases the voltage by 10 times. Since it only works with AC current the transformer goes in the circuit after the components that alter the current from DC to AC.
https://sciencing.com/dc-ac-power-converter-work-5202726.html
4) AC-AC converters: This type of converters are aslo called as the cyclo converters,they mainly used to converts Fixed AC to Variable AC.
AC/AC converters connect an AC supply to an AC load and thereby control the current the voltage and rms power of the load. they also convert AC voltage-current at one level to AC voltage-current at another level or AC voltage at one frequency to AC voltage at another frequency.
When We require a particular voltage and particular frequency for operating some special devices or machines. For speed control of inuduction motor AC to AC converters is used majorly. For getting a desired AC power supply from the actual power supply we need some converters called AC to AC converters.
Types of AC-AC converters:
The AC to AC converters can be classified into different types:
- Cycl converters
- AC to AC Converters with DC link
- Matrix Converters
- Hybrid Matrix Converters
https://www.elprocus.com/ac-to-ac-converter-working-and-supplies/
Question:2
Aim: To find 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'
Given data:-
voltage= 72 V
Rated armature current= 400 A
Ra= 0.5Ω, Motor constant = 0.7 Volt/sec
Chopper Switching frequency= 400 Hz
duty cycle =70%
Solution: We have the formula
ouput volatge= battery volatge*duty cycle i.e = 72*0.7=50.4v .so the vehicle voltage = 50.4
Now taking the torque equation= Tv=Vv.kø/Ra-Kø^2/Ra.w
now sub the given values in above equation
i.e Tv= 50.4*0.7/0.5-0.7^2/0.5*w by sloving we get 70.56-0.97w^2
But in the question the vehicle speed torque characteristics is given as, Tv=24.7-0.0051w^2
Now equating the above equations we get
24.7-0.0051w^2=70.56-0.97w^2
0.0051w^2+0.97w-45.81=0
so now sustituting the above equations in quadratic equation formula
x = −b + √(b2 − 4ac)/2a = -0.97+-√ 0.97^2-4(0.0051)(-45.85)/2*(0.0051)
we get 39.19 rad/sec
Question:3
Aim: To Develop a mathematical model of a DC Motor for the below equation using Simulink.
ω">ωω= V/Kϕ">ϕϕ -Ra/Kϕ">ϕϕ^2 .T
Given data: V= 50 ,Kø=0.7,Ra= 0.5
Output results:
Question:4
Aim: To Refer to the blog on below topic:
Induction Versus DC brushless motors by Wally Rippel, Tesla
Explain in brief about author’s perspective.
The above topic shows that the author ( wally rippel) describes about the induction vs brushless motors .in the intiall stage the author said that he was engineer at aerovironment wher he used to help develop the EV1 for general motors and he was featured in the documentary movie who killed the electric car and he also worked for the jet propulsion lab on Ev battery research.
Intially the author explain about the ICE in automobile industry he said the in new coming generations the EV will play the key role in the auto mobile industry mainly he mentioned about the Dc brush less motor and induction motor.He thought that the brush motor should be replaced by the brush less motor or induction motor and he aslo thought that batteries should be replaced by the Litium-ion batteries
He said that above mentiod motors and batteries are going to use in the future in Ev.Because the brushless and induction motor as some advantages wihich overcomes the problems in present ICE.
Brushless DC motor: The motor converts supplied electrical energy into mechanical energy. Various types of motors are in common use. Among all these Brushless DC motors (BLDC) feature high efficiency and excellent controllability and are widely used in many applications. The BLDC motor has power-saving advantages relative to other motor types.
We can expect to see the BLDC motors used in a wider range of applications in the future. For example they will probably be widely used to drive service robots small robots that deliver services in fields other than manufacturing.
Advantage of brush less motor:
The main advantages of a brushless motor over brushed motors are high power-to-weight ratio high speed nearly instantaneous control of speed (rpm) and torque high efficiency and low maintenance.
The author also said that the brushless dc motor prouduces zero starting torque which connected to fixed frequency.
Induction motor:
The author said that the in future generation the induction motor drives a forerunner of the 3-phase induction motor motor was invented by Nikola tesla sometime before 1889. unlikely 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. The essential difference between the two machines is with the rotor.
An induction motor is also called as asynchronous motor is an ac motor in which the current in the rotor needed to produce torque is obtained by electromagentic induction from the magentic feild of the stator winding. An induction motor can be made without electrical connections to the rotor.
Advantage of Induction motor:
It can be operated in harm conditions. Unlike synchronous motors a 3 phase induction motor has a high starting torque good speed regulation and reasonable overload capacity. the induction motor is a highly efficient machine with full load efficiency varying from 85 to 97 %
And main disadvantage of the induction motor is The power factor of the motor is very low during light load conditions. During light load conditionsit operates at a very low power factor.
From the total discussion the author said that brushless dc motor is going to play the key role in EV and aslo in HEV in upcoming days in automobile industry.
Conclusion:
We have succesfully completed the above required tasks
In case-1 we find the different types of power converters circuit used in electric and hybrid electric vehicle.
In case-2 we have find 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'
In case-3 we have prepared the mathematical model for dc motor using matlab simulink
In case-4 we have refred the blog on Induction Versus DC brushless motors by Wally Rippel, Tesla