Types of Electric Motors

Types of Electric Motors

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Electric Motor:

It is the one that converts the energy from the battery i.e. Electrical energy to Mechanical energy which can be used to drive the wheels in
electric vehicles.

Types of Electric Motors

 

Various  types of electric motors used in electric
vehicles:

  • DC Motors
  • BLDC Motors(Brushless DC Motors)
  • PMSM(Permanent Magnet Synchronous Motor)
  • Induction Motor
  • SRM(Switch Reluctance Motor) 

        

1.DC Series Motors:

 This is very basic motor.DC motors were
most widely used motor for the traction application in the early 1900’s and
because of  its highest starting torque,
its easy speed control and its capability to withstand the sudden increase in load, these motors are still used in our Indian Railways  but Brushes and commutators are used in DC motors. So there in sparking at breast side and because of by which brushes are
dying day by day, so there is need to replace
brushes and because of this the frequency of changing the brushes,
maintenance is very high and this is the biggest disadvantage of DC motors
and another thing is its speed regulation is quite poor so that’s why this
motor is used for Indian Railways only.

 Advantages:

  • Simpler
    Installation
  •  Generally
    a low cost motor option.

 Disadvantages:

  • Limited
    lifetime due to friction wear of the brushes.
  • Need
    converters to supply power to the motor.

 

2.BLDC Motors(Brushless
DC Motors):

    This motor is upgraded version of DC Motors. This DC motor replaced the rotor with the permanent magnets so there is
no need of brushes and commutators and that’s why these motors are called
Brushless DC Motors. AS the brushes are not there, the BLDC motors are able to
rotate at high speed and they are of course very highly efficient compared to DC
motors.BLDC motors running  speed is a
synchronous speed and its rotor is a permanent magnet. Three hall sensors are
used in BLDC motors.

   BLDC used in light weight vehicles such as
kinetic Green, three wheeler such as pigo and Volta automotive.

 Advantages:

  •  No
    sparks and less noise, as the brushes are absent.
  •   Less
    maintenance is needed.
  •  Its
    efficiency is quiet high,it is 85-90.
  •  
    Reduced
    size of the motor.

 Disadvantages:

  •  High
    cost of permanent magnets
  •  High
    heat weakens magnets.

 

BLDC  Motors in context of e vehicles:

There are two
types of BLDC Motors:

  •  Out runner type BLDC Motor:

      The specialty of this motor is its rotor
is outside and stator is inside.  Because
of this construction this motor are also known as Hub motors because the wheels
are directly connected to the exterior rotor. These types of motors
doesn’t require  the external gears systems. Some motors itself has the planetary gear that’s why these motors are choice of many
electric cycle manufacturers like lightspeed bicycle. Also this is the choice
of many two wheeler manufacturers  like
22 motors and nds Eco motors.

  •   In runner type BLDC Motor:

     These motors  are like conventional motors. Its  rotor is inside and stator is outside. As a
rotor is inside, it needs the external transmission system to transmit its power
to the wheels and because of this the Out runner configuration in quiet bulky  compared to In runner configuration.BLDC  In runner type used in ather scooter.

 

 3)PMSM(Permanent
Magnet Synchronous Motor):

  PMSM is an AC Synchronous Motor.As there
is no major difference between BLDC and PMSM motors when it comes to
construction and the motor control system but the only difference is nature of
driving current and the detection of the position of rotor as the BLDC motor is
working on the DC sources and the PMSM motor is working  on the AC sources. We are using three hall
sensors for the detection of rotor position
in BLDC motors and only single hall sensor is used for PMSM otherwise
PMSM and BLDC motors are quite similar.

   Many automobile  manufacturers are using this motor in their
hybrid e-vehicles Toyota, Nissan leaf,bmwi3,they are using the motor of PMSM as
the traction motor.

 Advantages:

  •    Permanent
    magnets are smaller in size.
  •  Because
    of absence of torque ripple, it makes these motors more efficient   than BLDC
    Motors.
  •  High
    Power Density

 Disadvantage:

  •  High
    cost
  •  Risk
    of demagnetization

 

4)Induction Motor:

  This motor is having very simple
construction. It requires very less maintenance  compared to other motors. There are no brushes
so there are very low losses. As there is no permanent magnet the speed control
of this induction motor is quiet easy and as there is no any  position sensor, we don’t require any switches.
The overall  complexity Is very much less
as compared to other motors. But the only thing is this is not the
lightest  and the most compact motor
amongst other motors. But when it comes to application, it is used in many
e-cars. Tesla is one of the leading company which is using the induction motor
as a traction motor for the propulsion in their electric cars and Tesla Model S
is the quiet good example of Induction motor.

 Mahindra Reva e2o also uses a three phase
induction motor for its propulsion.

Tata motors are
planning to use induction motor in their cars and buses even the two wheeler
manufacturers  like TVS, it will launch
its scooter which will use induction motor for propulsion.  Induction motor are very preferable choice
for performance oriented vehicles due to its cheap cost. Due to these factor, the Indian railway has started replacing the dc series motor with induction motor.

 Advantages:

  • Induction Motors are robust and can operate in any environmental condition
  • Induction motors are cheaper in cost due to the absence of brushes,commutators 

 Disadvantages:

  • Three phase induction motor have poor starting torque and high inrush currents.
  •  Power
    factor is      low during light load.

 

5)SRM(Switch
Reluctance Motor):

This is very good and power electronics
based motors. This motor falls under the category of variable Reluctance
motor.It is very simple in construction and a very robust mechanisms. It is very
suitable for the high speed application. It offers a very high power density
which is the requirement of today’s electric vehicles, this is because of
its  simple construction. It is very easy
to cool the motor.Once SRM enters the commercial market, it can replace PMSM and
Induction motor in future. Tesla model 3 uses the IPM(Internal Permanent
Model)SRM.

 Advantages:

  •  Self
    starting
  • High efficiency
  • Less heat
  • Doesn’t require DC supply

 Disadvantages:

  •  Complexity in control
  •  Noise level is high
Types of Electric Motors

 

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