Week-6 Challenge: EV Drivetrain
ANS-1 :-
Power converter circuits :-
Power converter circuits are considered as the key element in electric and hybrid electric vehicles.
the converters are used in EV/HEV for drivetrain's power source.
power converter gives the rated voltage and current to the elecrtic equipments like motor, battery, etc.
there are mainly three types of converters are in EV/HEV.
1) AC-DC Converter (On board charger) :-
AC-DC Converters are use to charge the vehicle with on board charger they don't need any external charger for the vehicles.
the converter converts the AC power to the DC power which require to charge the Betteries.
the battery needs to be charged using a direct current source,for this reason the AC-DC converter is employed in EV/HEV.
2) DC-DC Converter :-
this converter are use to rectify the proper voltage and current for the electric elements.
electric circuits which require high voltage or low voltage, as per requirement of electric element DC-DC converter are converte the power supply.
they mainly used in power control circuits.
3) DC-AC Converter (Inverter) :-
they use to convert the DC power to AC power for the electric equipments.
if motor requires the AC supply to operate then this converter is use in EV/HEV to provide the power supply to motor.
the power output from battery pack (DC current) is converted using inverter to be used in electric motor (AC current).
ANS-2 :-
Given data :-
Batterypack voltage (V) = 72 V
Rated armature current = 400 A
Armature resistance (Ra) = 0.5 ohms
Motor constant (K) = 0.7
Chopper switching frequency = 400 Hz
Duty cycle = 70% = 0.70
Solution :-
Vehicle output voltage (Vv) = Battery voltage (V) * Duty cycle
Vv = 72 * 0.70 ==> Vehicle o/p voltage (Vv) = 50.4 V
Now, Vehicle torque Tv = ((Vv-w*K)*k)/Ra
where,
Tv = vehicle torque (N-m)
Vv = vehicle voltage (volts)
w = steady state speed of vehicle (rps)
k = motor constant
Ra = armature resistance
Tv = ((50.4-0.7*w)*0.7)/0.5
Tv = 70.56 - 0.98*w
given equation,
Tv = 24.7 + 0.0051*w^2
now,
24.7 + 0.0051*w^2 = 70.56 - 0.98*w
0.0051*w^2 + 0.98*w - 45.86 = 0
w^2 + 192.2*w - 8992.2 = 0
By solving this equation we got two values,
w = 39 & w = -230.569
we take the positive value;
Steady state speed of vehicle = 39 rad/s
ANS-4 :-
the following topics are concluded from the topic :-
1) the auther discribe the dominance of IC engines in the world of automobile industry and also discuss different types of engines.
2) auther explain that all engines were simillar and it was up to user to select according to their requirement.
3) he also speaks about induction motor and brushless motor and present his view that these two technologies will be widely used for the coming years.
4) auther explain the working of 3-phase induction motor and a brushless DC motor.
5) auther explain the advantages and disadvantages of these two technologies.
6) induction motor advantages like it has no magnets. the motor has ability to start under load. no inverter needed.
7) the disadvantages of the induction motor is that it is not operate on DC. AC supply is must require.
8) shaft speed is propotional to line frequency. they are constant speed machine.
9) brushless motor advantages like much less rotor heat is generated with the DC brushless drive.
10) the peak point energy efficiency be a few percentage higher than the induction motor.
11) the disadvantages of DC brush less motor is that the machine size is higher.
12) finally the auther couldn't choose which drive is better than other but make it clear that DC brushless drives will likely continue to dominate in the hybrid and coming plug in hybrid markets and that induction drives will likely maintain dominance for the high performance pure electrics.