Week-6 Challenge: EV Drivetrain

1)

we use basically 3 types of power converters.

They are A. AC-DC converter

B. DC-DC converter

C. DC-AC converter

A. AC-DC Converter:

• AC-DC converter (Onboard charger) is used for charging the vehicle.
• As battery stores energy in the form of DC, so AC-DC power converter is required.
• They are generally used in PHEV and PEV type vehicles.

B. DC-DC Converter(Chopper):

• We know lights, indicators and other signal generators requires only low voltage (12V or 24 V)
• So the battery energy (DC type high range) will converted into Low voltage DC by DC to DC converter (Chopper).

C. DC-AC Converter (Inverter):

• DC-AC converter is used to convert the battery energy (DC type) to AC to supply the motor (AC motor used).
• Therefore, the converted energy (AC) is used for motor operation.

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

T_v =24.7+(0.0051)ω²

What is EV steady state speed if duty cycle is 70%?

Ans:-

As the torque formula is given, we need to find the speed in rad/sec. Use the other expression available which is given below:

Rated Armature voltage, V_A = 72 V

Rated armature current= 400 A

Ra= 0.5Ω

KΦ= 0.7 Volt second

Chopper Switching frequency= 400 Hz

T_v =24.7+(0.0051)ω²

For Duty Cycle, δ = 70%

Voltage = V_A × δ

= 72 × 0.7

= 50.4 V

We know,

Torque, T = KΦ/R_A*[ V_A - KΦ*ω]

By Substituting the given values,

Torque, T = (0.70.5)⋅(50.4−0.7w)(0.70.5)⋅(50.4-0.7w)

= 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 ω² (Given)

At T = T_V ;

70.56 – 0.98 ω = 24.7 + 0.0051 ω²

Or, 0.0051 ω² + 0.98 ω +24.7 -70.56 = 0

Or, 0.0051 ω² + 0.98 ω – 45.86 = 0

i.e., ω = 38.915 or −231.072

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

3)

4)

1. There is no such thing called the best engine. According to the personal requirements, we need to adapt the engine type.

2. In the course of time, Lead-acid batteries are replaced by Lithium-ion batteries.

3. In the course of time, DC brush motors are replaced by DC Brushless or Induction Motors.

4. In the course of time, Contactor Controllers are replaced by Modulating Inverters.

5. There is a bigger concern regarding the stable use of these elements mentioned above over the next few decades.

6. The author discusses the two technologies such as: 1. DC Brushless Drives and 2. Induction Motor with it's feature of operation.

7. He says brushless motors are useless motors without the inverter.

8. He also mentioned that the 3-phase induction motor has great utility but with several limitations.

9. The major limitation being, the Induction Motor can not operate from DC, and AC is a must.

10. Further, he compares the future trends which may occur in DC Brushless as well as in Induction motor.

Conclusion:

He concludes 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.