Regenerative Braking System in EVs

Regenerative Braking System
in Electrical Vehicles
Submitted by
Madhavan J
19TC0316
1
RAJIV GANDHI COLLEGE OF ENGINEERING AND TECHNOLOGY
Kirumampakkam, Puducherry.

Introduction
• Moving vehicles have a lot of kinetic energy, and when brakes are
applied to slow a vehicle, all of that kinetic energy has to go
somewhere.
• In Conventional Braking System that energy is wasted in form of
heat energy due to the friction.
• Regenerative Braking System is a technology through which we
can reuse that wasted energy.
• That is, the kinetic energy of the running vehicle is converted into
electrical energy.
Kinetic Energy of
Running Vehicle
Electrical Energy
2

Why Regenerative Braking?
• To understand that why we need a regenerative braking system, we
have to look into the FTP-75 Driving Cycle.
• The Federal Test Procedure, commonly known as FTP-75 for the
city driving cycle, are a series of tests defined by the US
Environmental Protection Agency (EPA) to measure tailpipe
emissions and fuel economy of passenger vehicles
• FTP-75 cycle is represented by two parameters,
⁃ Time (x-axis)
⁃ Speed (y-axis)
3

• Percentage of Braking energy to total energy is approximately 40%
for this drive cycle.
• By recovering this energy, we can improve the overall efficiency of
the vehicle.
• This can be done using Regenerative Braking System.
4

• Working of Regenerative Braking System depends on the speed and
torque of electric motor.
• If the directing of speed and torque of a motor is in same direction,
it takes electrical energy from battery and converts it into
mechanical energy(rotation).
• If the directing of speed and torque of a motor is in different
direction, it takes mechanical energy and converts it into electrical
energy.
• Now, how to know the direction of speed and torque?
How it works?
5

• If the stator speed is greater than rotor speed, torque is positive and
its direction of torque is same as direction of speed.
• If the stator speed is less than rotor speed, torque is negative and its
direction of torque is opposite to direction of speed.
6

Let’s consider,
Ns - Stator Speed or Synchronous Speed
N - Rotor Speed
• Torque is directly proportional to Slip of the motor.
⁃ If slip is positive, torque is also positive
⁃ If slip is negative, torque is also negative
7

• We also use friction brakes to make the speed zero.
• In this system, the motor drives the wheels during acceleration, but
the wheels drive the motor while decelerating.
• This two-way energy flow allows the motor to act as a generator,
resisting the rotation of the wheels and creating electricity to
recharge the vehicle's battery.
8

• There are two conditions when regeneration occurs:
1. When the driver applies the brake pedal
2. When the driver releases the accelerator pedal, and the vehicle
is coasting
• In both cases, the system creates electricity to recharge the battery.
Drivers can view this regenerative effect on the vehicle's charging
gauge.
• The amount of electricity the system generates is proportional to
the level of braking force. That means the stronger the braking
force, the greater the electrical current.
• Ultimately, the amount of energy the system captures is dependent
on the vehicle's speed and the duration of brake application.
9

• One-pedal driving is possible due to the regenerative braking
systems in electrified cars.
• During the regenerative phase, the magnetic resistance of the
electric motor increases and creates a braking force. This added
friction slows the vehicle down.
• If an emergency stop is necessary during one-pedal driving, the
driver must use the standard hydraulic brakes. No matter the
situation, the driver can always apply the standard brakes to bring
the vehicle to a stop, whether that be for a pedestrian, vehicle, or
any other danger or obstruction on the roadway.
• One-pedal driving is a convenience feature that the driver can
override at any time.
One Pedal Driving
10

• Each year, new EV or hybrid models arrive with increasingly
sophisticated regenerative braking systems, improving the amount
of energy these systems can capture.
• In some cases, the latest regenerative braking systems can recover
up to 70% of the kinetic energy otherwise lost during braking.
• Depending on how much an owner drives their vehicle, this can add
up to hundreds of miles of extra electric range throughout the year.
• It reduces trips to the fuel pump for hybrids and lessens the need
for pure EVs to plug into the power grid.
Efficiency
11

• Increases the vehicle range.
• Brake pads and rotor may last longer.
• Environmental friendly
• Lower maintenance due to an efficient electric motor.
• Better Performance.
• Reduces the wear and tear of the system.
• Saves money.
Advantages
12

• Potentially less stopping power.
• Less effective at lower speeds.
• Brake pedal may feel different.
• It affects the battery lifetime, but can be improved.
• Need a conventional braking system in emergency conditions.
• Although it saves money, it increases the initial cost of the vehicle.
Disadvantages
13

• It can be used in Electric cars as well as hybrid cars and IC engine
cars.
• Also can be used in petrol or diesel engine cars.
• It can be used in electric cycles, electric bikes and electric
skateboards.
• It is also used in major new high-speed trains.
• Upcoming all ev cars use the regenerative braking system.
Applications
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• Electric Vehicle integrate various systems to optimize efficiency,
and regenerative braking is a vital component of that overall
equation.
• Besides minimizing energy loss and extending electric range,
regenerative braking systems lengthen brake life due to their low
wear and tear characteristics.
• The benefits of this technology are evident and help make green
vehicles ever more appealing to consumers.
Conclusion
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• wikipedia.org/wiki/Regenerative_braking
• Dr. Tirupathiraju Kanumuri, (2019), “IM41 Regenerative Braking
of Induction Motor [Video]”, YouTube,
https://www.youtube.com/watch?v=fnBlXmPsbXg
• Skill-Lync, (2020), “How does Regenerative Braking work?
[Video]”, YouTube,
https://www.youtube.com/watch?v=WA32wMdd28g&t=3s
References
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Regenerative Braking System in EVs

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