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Now a days world is plagued with global issues like fuel shortage, global warming. No doubt Electric Vehicles are the solution for fighting against these issues. As convectional vehicles has fuel as energy source and engine as prime mover, Electric vehicles uses battery as energy source and electric motor as the prime mover to drive. The various options available for driving electric vehicle are DC motor, induction motor, and Brushless DC motors.

In Electric Vehicle, there should a portable power supply. Hence we can use Battery to power the vehicles and DC is the default power supply.

DC Motors: These motors constitutes of Brushes and commutator which will act as a mechanical position sensor on rotor and supplies the power supply to corresponding stator winding so that there will be a forward torque produced in the motor. Advantage of this motor is its constant torque characteristics at various rotor positions. But following are the disadvantages of this motor
The Brushes will be wear out due to constant contact between rotation and stationary portions of motor.
The commutator segments might get shorted due to the burned carbon precipitated in between which might result in unbalancing of the motor operation.
Low operating efficiency


Hence, a DC motor needs a periodic maintenance to prevent it from permanent damage.

Induction Motors: Induction motors are powered by single phase or three phase AC power supply. The stator is wound with three phase winding and when powered by 3-ph AC voltage, a rotating magnetic field is produced in the motor air gap which will produce the required torque on the shaft by dragging the current from the mains.
There are many advantages seen in Induction motors when compared to DC motors i.e. high efficiency, least maintenance. But to realise this motor to drive an electric vehicle, DC power in battery should be converted to AC and then fed to the motor via controller which will make the system bulky and expensive.

Brushless DC motors: They also called as BLDC motors. These are the next version of DC motors. These motors evolved after research to eliminate the disadvantages of convectional DC motors and coined as Brushless DC motors. Permanent magnets are used in rotor. As its name conveys this motor doesn’t have brushes and commutator. Hence there will not be any wear and tear while operating and hence no maintenance required.

Operation: BLDC Motor uses hall sensors for identifying the rotor position and give the feed back to controller so that controller will excite the stator windings accordingly so that the motor run in the required direction.

Advantages of BLDC are as follows
As permanent magnets, this motor has high power density. i.e. Motor size is low for a given power.
Absolutely No maintenance required.
High torque production at the shaft.


Now a days, research being done even to remove the hall sensors and developing sensor-less BLDC motor which will be even more robust for Electric vehicle application.

Written by Murali , founder and promoter of EV Forums
 
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