Week-6 Challenge: EV Drivetrain

Aim:

1.To tell the types of power converters circuits employed in elevtric and hybrid electric vehicles.

2.With the given datas and the given equation find the EV steady state speed.

3.Explaination about the Induction versus DC brushless motors by Wally Rippel,Tesla.

Explanation:

1.There are of about four types of power converters circuits,

• DC to DC - This converts one value of DC voltage into other value of DC voltage(Ex:Copper)
• AC to DC - These convert AC voltage into regulated DC voltage. The form and magnitude are regulated. Usually used to get regenerated power from vehicle to the battery.(Ex:Rectifiers)
• DC to AC – These convert DC voltage into regulated AC voltage.Form and magnitude are regulated.Usually employed when AC motor is used to drive the vehicle.(Ex:Inverters)
• AC to AC – Regulated AC output from AC input.

2.As the duty cycle is 0.7, the effective voltage to the motor is 72*0.7=50.4 V

The equation representing characteristics of DC motor is

`T=V.k phi/R - Kphi^2.omega/R`

comparing this equation with the given equation,

`Tv=24.7+(0.0051)omega^2`

gives

`V.kphi/R -kphi^2.omega/R=24.7+(0.0051).omega^2`

`(50.4*0.7)/0.5-(0.7^2*omega)/0.5=24.7+0.0051*omega^2`

solving for w gives-

`0.0051omega^2+0.98omega-45.86=0`

w=38.95 rad/s ,which is steady state speed.

3.The blog gives a brief description of the difference between induction motors and DC brushless motors.

DC brushless motor:

• Uses permanent magnet as rotor, to produce magnetic field.
• Stator core involves current flowing within the windings to produce torque interaction between stator and rator requires inverter for operation.
• Requires angle position sensor for operation does not produce much heat, cooling is easier.
• Has higher peak efficiency point.
• Permanent magnets are expensive and the motor cost increases as a result. Handling becomes difficult because of the strong magnetic forces between ferromagnetic materials and magnets.
• Easier to control for lower to medium performance ranges.
• Difficult to alter motor parameters such as field strength because of permanent magnets.
• Speed is controlled by PWM method
• As the motor size increases, magnetic losses increases proportionality and load efficiency drops.

AC induction motor:

• Rotor is stacked steel laminations.
• Stator is Distributed windings inside stator core.
• It has AC 3 phase voltage supply.
• There is no inverter necessary needed to control it, it can run on 3 phase power itself.
• It can generate starting torque from the onset when connected to fixed frequency supply.
• It can run only on constant speed.
• More rotor heat is generated by eddy currents.
• It has lower efficiency and can operate at 0.85 power factor.
• Magnetic field can be varied.
• Magnetic losses does not vary with increase in size.
• It is less expensive because of no magnet is been present in it.

Result:

Thus the explanations for all the questions is been given.