EV Basics Electric vehicle motor selection guide | ev bldc motor
Selection of motor for EV
An Electric motors are the most important part of all power train system used in electric vehicles. Thus its make the electric vehicle motor selection very critical to get desired performance form EV. In current scenario we use many types of electric motors for Evs like electric cars, erickshaw, e bike etc as per their applications.
Commonly motors used in electric vehicles are broadly classified as
AC Motors
DC Motors
AC Motors or Alternate current motors:
Most popular form of AC motors used in electric vehicles is
3 Phase permanent magneto AC Induction motors.
This motors most popular and most a preferred choice between various types of motor used in electric vehicle. All most all electric car manufactures. because of their specific features well suited to electric vehicles:
Very high efficiency 88% to 96%
These motors is very compact in size
Light in weight
Low maintenance required thus high durability and reliability.
Draw Back:
Low availability ( very few manufactures make this motor because of complex design)
High in Cost (Thus use is restricted in the 4-Wheeler /e cars)
Require AC power and variable frequency controller which makes controller circuit complex and very costly.
DC Motors or direct current motors:
This motor is very popular and widely used due to its property of delivering high starting torque, which is very much required in electric vehicle. Although current draw by this motors is proportionally, one should also consider this point during designing of the battery pack for EVs.
Some common used DC motors area in Evs are
Brushed DC Motors
BLDC Motor(Brush Less DC Motor)
PMBL Motors ( Permanent Magneto Brush Less Motor)
This motor selection criteria basically based on the easy availability of motors .
Brushed DC Motors:
This is the oldest DC motors which is very less used in current Evs. As the name this motor consists carbon brushes. This motors have efficiency of 75-82%. Its a basically a outdated technology
Advantages:
High Torque
Low Cost easy availability.
Drawbacks
High maintenance due to carbon brush wear-out
Low efficiency
BLDC Motor:
This motor is developed form of brushed Dc motors and dose not consist any carbon brush. BLDC motors have efficiency of 78-85%. This motors is one of the preferred choice for ev conversion kit motor.
Advantages:
High Torque
Easy availability
Low maintenance
Drawbacks
High cost than brushed dc motor
It should be keep in mind before making selection of bldc motors for ev application that its commonly comes in the option of 3000rpm and thus high torque. So the designing of power train according to the lower rpm.
PMBL Motor
Most Efficient in all DC motors
Heavy duty & Durable due to use of magnet in rotor instead of field winding
Compact Size due to the use of magnet
Low in Weight
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| PMBL Motor Rotor |
Drawbacks
Due to use of magnet its power rating is restricted to certain limit due to magnet power limitation. thus cant design for higher rating. thats why its use in electric vehicles is limited.
Higher Cost
Limited availability
You can find the all above motor for electric vehicles in the option of geared and non geared motor as per you application/ requirement.
Construction of Permanent Magnet Brush less motor:
PMBL motor is different with bldc motors in terms of rotor design. where as the design of stater is same for both the motor. Permanent Magnet bl motor rotor is inserted with the strong magnet on its periphery instead of field winding which generate required magnetic field for rotor rotation. This magnet reduced the induction loses inside the motors in enhance efficiency and permits pmbl motor compact size and low weight.
Different Motor efficiency Parameters:
Permanent Magnate 3 Phase AC Induction Motors
Efficiency Varies from 88 % – 96%
BLDC Motors
Efficiency Varies from 74% - 85%
Permanent Magnet Brush Less motor
Efficiency Varies from 80% - 89%
Mounting Types of all DC motors:
Hub Motor
The biggest benefits of dc hub motors is that we can mount this motor directly in the wheel thus its require very less space or only occupy the wheel. Simple in mounting and easy to convert conventional bike in to electric one.
Foot mounted/ Flange mounted motor:
This bldc motor can be mounted in the free space in the bike or car and require arrangement like chain or belt for power transmission. Its recommended to belt drive in higher rpm transmission like in scooter where wheel diameter is less. In higher wheel diameter like in motor cycle we can use the chain drive because low rpm transmission required due to bigger wheel.
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Frequently asked Q & A
How do I choose a motor for my electric car?
There are lots of parameter like desired Speed, Power, Torque, Durability, efficiency, size etc. But most important practical parameters are cost, availability and warranty need to consider
Which motor is best for electric vehicle?
For e bikes hub motor is best because of direct fitment in wheel and direct drive. But for electric car of moderate weight BLDC motors is best
Its very from required performance of EV. Although if for a car of 800Kg -1000Kg , for moderate performance motor fitted with direct differential one should consider 6-8Kw bldc motor.
Which induction motor is used in electric vehicle?
In modern electric vehicle 3 Phase permanent magneto AC Induction motors is used by maximum manufacturer in electric car.
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