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Electric Vehicle Propulsion - Coggle Diagram
Electric Vehicle Propulsion
AC Motor
Parts for Creating AC Motor
Rotor
The part that is connected to the output shaft
For asynchronous motor : squirrel cage rotor
• Use for induction (asynchronous) motor
• Harness electromagnetism from stator to generate motion
• The shape of their rotor looks like a cage
• Two circular end caps are joined by rotor bars
Asynchronous motor : Wound motor
• Same principles as the squirrel cage motor but differs in the construction of the rotor
• The rotor is made up of windings which terminate at slip rings on the shaft
• Used in special applications where a high starting torque is required
Wound rotor coils are connected through slip rings and brushes to external variable resistors
• The rotating magnetic field induces a voltage in the rotor windings.
For synchronous Motor : Permanent magnet
A permanent magnet mounted on the rotor
The magnet has its own magnetic field that interacts with the rotating magnetic field of the stator
The north pole of the rotating magnetic field attracts the south pole of the magnet, and vice versa
As the rotating magnetic field rotates, it pulls the magnet along causing it to
rotate
Stator
Main function is to transmit a rotary magnetic field for interacting through the rotor
Bearing
Fan Blades
End Bell
Wiring Cover
Motor Frame
End Bell
AC Motor relies on interaction of a revolving magnetic field created in the stator by AC current, with an opposing magnetic field
induced on the rotor (Asynchronous motor)
Provided by a separate DC current source (synchronous motor)
Synchronous motor VS Asynchronous motor
Synchronous
Operates on the principle of magnetic interlocking between rotor and stator field
No slip , Speed of motor = Ns
Speed does not vary with varying the load connected to the motor
Not self-start and require extra
windings for starting the motor
Requires extra DC source to
energize its rotor winding
Input voltage supply does not vary the speed or torque of synchronous motor
Fluctuations in the main supply voltage do not affect synchronous motor operation
Initial cost is greater than
asynchronous motor
Asynchronous
runs on speed less than the
synchronous speed
Operates on the principle of electromagnetic induction between stator and rotor
Has slip, Speed of motor < Ns
Speed does vary with varying the load connected to the motor
Self-start and do not require extra
mechanism
Does not require any extra source
Input voltage supply can be used to vary the torque and speed of the motor
Mains voltage fluctuation affects its speed and operation
cheap
DC Motor
Brushed DC Motor
Operate on direct current (DC)
Consist of
Rotating part (rotor) called the armature (winding similar to wound rotor)
Stationary part (stator) introduces a magnetic field by either permanent magnets or field windings which act on the armature
Construction of DC Motor
Commutator (a rotary electrical switch that periodically reverses the current between the rotor)
Armature (Electromagnet coil)
Shaft
Stator (This can be permanent magnet or electromagnet)
Brush (Keeps in contact with commutator and allow for current to flow into the armature)
Working principle of DC motor
• When DC current flow through the rotor wire, magnetic flux would be created around the wire.
• The magnet flux of wire would interact with the magnet field from the permanent magnet causing it to rotor to rotate.
The direction of the current flow in the rotor wire would change due to the commutator and bush as the rotor rotates.
Brushless DC Motor
Does not have commutator and brush compared to brushed DC motor
2 type of rotor and stator arrangement
Inner Rotor Motor
Heat is easily dissipated from electromagnet coil winding as it is positioned outside. Designed to produce high torque.
Outer Rotor Motor
Heat is from electromagnet coil winding is trapped within the permanent magnet. Designed to operate at lower rated current and low cogging torque
Working principle
Torque is produced because of the interaction between the magnetic field generated by the stator coils and the permanent magnets. (ex: positive attract to negative)
In order to keep the motor running, the magnetic field produced by the windings should shift position, as the rotor moves to catch up with the stator field.
Major Part for motor
The Stator (Stationary part)
The rotor (rotating part)
Motor Characteristics
Torque-speed characteristics
Starting torque
The minimum torque produced during acceleration from standstill to operating speed
Pull-up torque
The torque produced at zero speed
Breakdown torque
• The maximum torque that the motor can produce before stalling
Full load Torque
The torque produced at full load speed that gives the rated output of the motor
Motor Torque and power
Motor Torque
The amount of rotational force that the motor develops
Measure in either in-ibs or N-m
Motor Power
Defined as the rotational speed of the
motor multiplied by the torque
Horsepower = torque x speed / 50.1503
Motor Efficiency
The ratio of mechanical power output to the electrical power input and is usually expressed as a percentage
Efficiency = Mechanical output / electrical input x 100%
Motor Losses
Core losses
Comprised of Hysterisis losses (the energy required to magnetize the core) and eddy current losses in the stator core (magnetically induced circulating currents
Stator losses
Caused by the I2R heating effect of current flowing through the resistance of the stator windings
Rotor Losses
caused by the I2R heating effect in the rotor
Friction and windage losses
Contributed by bearing friction, wind friction on the rotor assembly, and the motor’s cooling fan load
Stray load losses
Other losses that are not mentioned earlier