Week-6 Challenge: EV Drivetrain
Solution1-
Power Electronic Converters:- A power converter is an electrical or electro-mechanical device for converting electrical energy. A power converter can convert alternating current (AC) into direct current (DC) and vice versa.
There are 3 types of power converters which are mainly used in EVs and HEVs:-
- AC to DC Converter (Controlled Rectifier)
- DC to DC Converter (DC Chopper)
- DC to AC Converter (Inverter)
AC to DC converter or Rectifier:(On board charger)
a.EVs and HEVs get their propulsion power from an external electricity source which is AC.
b. Mainly used as an On-Board Charger
c. It converts AC power from an external charging source into a DC voltage that is used to charge the battery pack in the vehicle.
d.It also perform charge rate monitoring and protection.
DC to DC Converter (DC Chopper):
a.Mainly used as a Chopper either to Step Up or Step Down the DC voltage as per
requirement.
b. DC-DC converters can be used to interface the elements in
the electric power train by boosting or chopping the voltage
levels.
DC to AC Converter (Inverter):
a.it is mainly used to convert direct current DC to alternating CUrrent Ac as the name suggests.
b.The power output from battery pack is converted using inverter to be used in electric motor to operate on AC.
Solution 2:-
Given That:-
By Substituting the given values,
Torque, T =
= 1.4 × (50.4 – 0.7 ω)
= 70.56 – 0.98 ω
T = 70.56 – 0.98 ω and
T v = 24.7 + 0.0051 ω 2 (Given)
At T = Tv;
70.56 – 0.98 ω = 24.7 + 0.0051 ω 2
Or, 0.0051 ω 2 + 0.98 ω +24.7 -70.56 = 0
Or, 0.0051 ω 2 + 0.98 ω – 45.86 = 0
i.e., ω = 38.915 or −231.072 rad/sec
Since Speed cannot be negative, we will consider that the EV steady state speed if the duty cycle is at 70% is
ω = 38.915 rad. S -1 or 371 rpm
Develop a mathematical model of a DC Motor for the below equation using Simulink.
ωω= V/Kϕ -Ra/Kϕ^2 .T
requirements based on price and performance and that is also the case with electric vehicle drives.
He points out the evolution of components in EV technology from Lead acid batteries, DC brushed motors
and contactor controllers to Lithium-ion batteries, BLDC and Induction motors to even inverters.
He strongly believes that both induction and BLDC motors will have tough competition in coming years,
because each will have its loyal proponents and religious detractors.
He compares the design of both BLDC and Induction and observes that its only differences are in Rotors
He also adds the importance of an Inverter in variable speed application of Induction motor to operate
flawlessly.
He even comments on the efficiency and performance characteristics of both BLDC and Induction motors
He explains that BLDC generates much less Rotor copper loss and its ability to operate at unity power factor
helping to achieve peak point efficiency whereas the best power factor available for Induction motor is
around 85% making it few percentages point lower efficient
He also criticizes the drawback of BLDC motors which is the difficulty in lowering its magnetic field strength
during low torque values to achieve best efficiency because to minimizes the magnetic field strength, it is
also required to minimize the eddy and hysteresis loss.
Furthermore, he compares the cost, performance, and reliability of both motors as Induction motor is
Cheaper due to absence of PM’s, Performance oriented but requires complex algorithms for controlling and
achieving stability is difficult causing increased development cost, Whereas BLDC is expensive but very easy
to control, also very efficient and high stability
and PHEV segments while Induction motors dominate high performance EV segments. But he anticipates
that both Induction and BLDC motors live and work side by side during the coming golden era of hybrid and EVs.