Types of motors
Electric motors can be classified in a variety of ways
 Operating characteristics such as
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The source of electric power,
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Type of rotor winding,
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Type of motion,
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Control pattern,
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The magnetic flux orientation,
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Structure topology,
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Power rating,
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The cooling methods.
Types of Electric Motors used in Electric Vehicles:
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DC Series Motor
Brush-less DC Motor
Permanent Magnet Synchronous Motor (PMSM)
Three Phase AC Induction Motors
Switched Reluctance Motors (SRM)
1. DC Series (DC Brushed ) Motor :
High starting torque capability
Advantages

Easy speed control

It can also withstand a sudden increase in load.
Drawback

high maintenance due to brushes and commutators.

Frictional losses
Applications
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Electric Vehicles
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Drones
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Robots and
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Some other Electronics Devices.
2. BLDC (Brush-less) Motor :
Same as Dc motor but it does not have the commutator and brush arrangement.
Elimination of brushes over armature for switching (commutation) it becomes more complex and is
performed electronically using additional set of electronic components (like an amplifier triggered
by a commutating component like an optical encoder) to achieve motion.
Commutation algorithms for Brush-less DC motors can be divided into two:

Sensor-based
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senseless commutation.
 Sensors based (e.g hall sensor) are placed along the poles of the motor to provide feedback to
the control circuitry to help it estimate rotor position. There are three popular algorithms
employed for sensor-based commutation.

Trapezoidal commutation
Advantages
i. Control Algorithm is simple
ii. Only two phase is needed to active at time
iii. Less switching losses
Disadvantages
a. Torque ripple at every commutation
b. Torque produced is less
c. Acoustic and electric noise

Sinusoidal commutation
Advantages
i. No torque ripple in commutation
ii. Smooth motion
iii. Maximum Torque is produced
Disadvantages
a. Possible to have three phase on same time
b. Higher Switching losses
c. Control Algorithms are complex and mathematically intensive

Vector (or field-oriented) control.
Each of these control algorithm has its pros and cons and the algorithms can be implemented in
different ways depending on the software and the design of the electronics hardware to make
necessary changes.
 Senseless commutation.
instead of sensors being placed within the motors, the control circuitry is designed to measure the
back EMF to estimate rotor position.
This algorithm performs pretty well and is at a reduced cost as the cost of the hall sensors
is eliminated but its implementation is a lot more complex compared to the sensor based algorithms.
Advantages

High starting torque

High efficiency around 95-98%

BLDC motors are maintenance free as the commutation is done electronically.
 Factors to consider when selecting between the Brush-less and Brushed DC Motors
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Duty Cycle/ Service Life
Efficiency
Control/Actuation

Cost
BLDC motors further have two types:
Out-runner type BLDC Motor (Hub motor):
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Rotor of the motor is present outside and the stator is present inside.
does not require external gear system
In few cases, the motor itself has inbuilt planetary gears.
motor makes the overall vehicle less bulky
This motor is widely preferred by electric cycle manufacturers like Hullikal, Tronx,
Spero, light speed bicycles, etc.
It is also used by two-wheeler manufacturers like 22 Motors, NDS Eco Motors, etc.
In-runner type BLDC Motor:
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The rotor of the motor is present inside and the stator is outside like conventional motors.
Motor require an external transmission system to transfer the power to the wheels,
The out-runner configuration is little bulky when compared to the in-runner configuration.
Many three- wheeler manufacturers like Goenka Electric Motors, Speego Vehicles,
Kinetic Green,
Volta Automotive use BLDC motors.
Low and medium performance scooter manufacturers also use BLDC motors for
propulsion.
3. Permanent Magnet Synchronous Motor (PMSM)
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Similar to BLDC motor which has permanent magnets on the rotor.
Characteristics like high power density and high efficiency.
The difference is that PMSM has sinusoidal back EMF whereas BLDC has trapezoidal back
EMF.
PMSM is the best choice for high performance applications like cars, buses.
Stiff competition between PMSM & induction motors due to increased efficiency
PMSM is also costlier than BLDC motors.
They have a constant magnetic field in the rotor. So induction cannot be used.
Most of the automotive manufacturers use PMSM motors for their hybrid and electric vehicles
For example, Toyota Prius, Chevrolet Bolt EV, Ford Focus Electric, zero motorcycles S/SR,
Nissan Leaf, Honda Accord, BMW i3, etc use PMSM motor for propulsion.
4. Three Phase AC Induction motor :
Asynchronous motor is a machine whose rotor rotates at the speed less than the synchronous speed.
N < NS
 Simple and rugged construction
 Low cost and minimum maintenance
 High dependability and sufficiently high proficiency
 Needs no additional starting motor and necessity not to be synchronized
Advantages:
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Low Cost
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Low Maintenance Cost
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Ease of Operation due to no connection to rotor
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Speed Variation constant
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High Starting Torque
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Durability is high
Disadvantages:
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Throughout the light load situation, the power factor is extremely less and it draws a huge
current. So, the copper loss can be high which decreases the efficiency throughout the
light load situation.
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The squirrel cage induction motor’s initial torque is not low.
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This is an invariable speed motor and this motor is not applicable where uneven speed
needs
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This motor speed control is not easy
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This motor includes a high starting inrush current which will cause a reduction within
voltage at the beginning of time.
Applications
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Pumps
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Compressors
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Small fans
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Mixers
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Toys
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High-speed vacuum cleaners
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Electric shavers
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Drilling machines
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Lifts
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Cranes
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Hoists
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Large capacity exhaust fans
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Driving lathe machines
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Crushers
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Oil extracting mills
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Textile and etc.
5. Switched Reluctance Motors (SRM)
Torque pulsations are inherent in SRM’s due to the doubly salient structure. Minimized torque ripple
design of a SRM of the machine and its sequential excitation.
Advantages

A switched reluctance motor offers many benefits against other types of
electric motors because of its control flexibility, simple structure,
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Lower cost
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High efficiency.
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The lack of winding or permanent magnet on the rotor means that an SRM is appropriate
for extremely high speed applications, and can withstand high temperatures.
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Rugged and simple structure and low manufacturing cost
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if a fault occurs in any one winding or phase, the motor can still work
but at a reduced load.
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Disadvantages
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non-linear characteristics of magnetic saturation makes it complicated
to accurately control its torque.
high noise, vibrations and torque ripple.
requires advanced control methods when compared with other AC and DC motor drives.
Motors
Rotor
BLDC
Permanent magnet on
rotor
PMDC / DC
Winding on rotor
PMSM
PM on rotor
AC Induction motor
Copper/Aluminium
bar
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Squirrel cage
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Wound/slip ring
Stator
Coil winding's
PM on stator
Coil winding's
Coil winding's
Controller
Controller is required
No controller is
required
Controller is
required
Various control
operations
Torque
Suitable for low
speed high torque
applications
High speed range
compare to DC
Suitable for low
torque application
Higher torque
compared to
BLDC
Higher speed
range & Eff.
Comparatively Low
from PMSM
Speed
Lower speed range
due to mechanical
imitation of brushes
Life
10k-20k hours
2k-5k hours
10k-20k hours
30k-40k
Efficiency
90%
60-70%
High eff. Up to
92-96%
1.Sinusoidal
Drive with
FOC.
2.Trapezoidal
with Back EMF
Sensing
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With sensor
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Sensor-less
85-96%
Back EMF / Hall
effect sensor
Little to no
maintenance
Periodic maintenance
require
Very efficient
heat dissipation
Very Efficient
Low electric
noise generation
Audible vibrating
magnet and fan
Higher
manufacturing
cost
Suitable for
controlled
environment
Very low
manufacturing cost
comparatively
Suitable for controlled
environment
Low weight
relatively
Higher weight
3 & 4 wheels
4 Wheeler's and some
of the heavy
comercial
Commutation
method


Rotor
position
detection
Maintenance
Heat
Dissipation
Noise
Cost
Operation
environment
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
Sinusoidal Drive
with FOC.
Trapezoidal with
Back EMF
Sensing
Uses mechanical
commentator to
reverse polarity of
the armature
electromagnet
With sensor
Sensor-less
Not Required
Little to no
maintenance
Superior thermal
characteristic result
in better heat
dissipation
Low electric noise
generation
Higher
manufacturing cost
due to complexity
Suitable for
controlled
environment
Periodic
maintenance
require, can replace
brushes for extended
life if necessary
Winding's on rotors
results in low hear
dissipation
Audible noise of
brushes during
rotation
Low manufacturing
cost
Weight
-
Easily able to
operate in extreme
environment due to
lack of electronics
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Applications
2 & 3 Wheeler's
2 wheeler