Week-6 Challenge: EV Drivetrain
EV LIVE BATCH 21
QUES.1
1. Rectifiers:
The rectifiers are used in AC-DC conversion stages of Plug in EVs(PEV) where the grid electricity is firstly met with this device.
The grid voltage obtained from the plug is 110V/60 or 220V/50Hz single-phase ac input in household application of PEV Rectifiers are analysed in ideal circuit topology and uncontrolled or controlled power switch topologies
2. Power Converters:
Power converters are classified according to their input and output types namely DC-DC Converters and AC-AC Cycleconverters.
DC-DC Converters are designed to increase or decrease the input voltage stage to desired value at the output.
Therefore, a device known as Buck Converter or step-down converter decreases the output value according to a high input voltage while,
Boost Converter or step-up converter generates an increased output voltage
The cycloconverters are used to convert input power at one frequency to output power at a different frequency. This con also be achieved by inverter.
Besides the unidirectional dc-dc converters, Bidirectional Converter Topologies are also being used.
When the EV driver zwiched into broking mode the batteries are charged by electric motor owing to bidirectional structure of converter.
Therefore, the bidirectional do de converter will be the key device in EVs
3. Controller and Sensors:
Almost all the power electronics in PEV require control signals as met in industrial applications.
Conventional linear control such as PID controller can no longer satisfy the stringent requirements placed on high-performance EV's.
The required control signals are generated by Microcontrollers and commutate power electionic devices with switches to provide fixed speed or torque
Pulse Width Modulation technique is adopted by controllers to cotain the instant control action,
interface ectronic devices are used besides Current and Voltage sensors located in the related parts
4. Inverters
In IVs, Inverters or used for DC-AC conversions. They are used to provide the required AC voltage and/or currunt for ac motors from DC battery supply, and consequently,
The inverter control algorithms perform motor control operations in terms of torque and speed inverters are considered as voitage source Inverters (V) and current source inverters (CS)
According to the type of output generation where VSIs are widely used in many industrial applications
The Latest Power Electonics as tv propulsion is used in the form of a Resonant DC-link inverter for ac motor driving operations.
These resonant dc-link inventors have either a parallel or series resonant circuit, thus providing the raging (ZVS) or a currentswitching (ZCS) condition
It facilitates the inverter to operate in switching mode to decrease the switching losaes and to increase the efficiency
The auxilliary circuit helps enable the load to be swung to the opposite roll to a zero turn-on voltage
The auxilliary circuit is not included, then it very difficult to ensure a zero turn-on voltage due to load current constraints.
QUES. 4
The author starts by clearly stating that all engines are not alike, and there is no one best engine, which is similar to electric drives.
With time technologies have developed which could be said for today's technologies that they might get better, as we can see
Lead batteries replaced by lithium, DC brush motors replaed by DC brushless or induction, Contactor Controllers with modulated inverters
Author was focusing on the similarities and the differences between DC brushless motors and Induction motors
So, brushless motors need an inverter for current control, which is not required in IM
from stator view, 3 phase IM and DC brushless motos are identical, both drives use 3-phase modulating inverters. they vary by the rotor and inverter control, and digital sensors
For Ideal brushless, B field should be adjusted to reduce I^2 R losses, but there is no easy way of changing B with permanent magnets. whereas, in IM, no magnets are there therefore, B field is adjustble. this increases the performance
IM is favoured for high performance and average effeciency is better if not peak effeciency. It will retain a cost advantage over permanent magnet machines, but achieveing stability is difficult due to complex control laws.
In the end, the autor was clear that, DC brushless will dominate hybrid,and plugin hybrid, Induction drives will maintain dominance for high-performance pure electric.
But, the main conclusion he came to was:
If the hybrids become more electrically intensive and as there performance level increase, DC and IM will live and work side by side in the near future of hybrid and electric.