Transcript Braking Systems - Faculty Of Engineering And Technology

University of Jordan
Faculty of Engineering and Technology
Electrical Engineering Department
Electric Drive EE 582 Project
Supervisor:
Prof. Mohammad Zeki Khedher
By:
Mostafa Walid Ali Alzahlan 0110486
Thabet Bassam Alalami
0095612
By: Mostafa W. Alzahlan
Braking Systems
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• Super capacitor regenerative braking
system.
• Regenerative braking systems in
locomotives.
• Regenerative braking systems in cars.
• Regenerative braking systems in scooters.
• KERS is used in F1 cars.
• Electric motor braking.
By: Mostafa W. Alzahlan
Applications of regenerative braking
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Super capacitor accept and release charge more
quickly and can be discharged and recharged
many times and with have longer life time than
a battery. For example in MAZDA car the unit
can accept a full charge in just 8-10 seconds.
The capacitor may take up to about 113s for
discharging when the load is at minimum at
about 18A.
By: Mostafa W. Alzahlan
Super capacitor regenerative braking
system
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By: Mostafa W. Alzahlan
Regenerative Braking with super capacitor unit in MAZDA A-6
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Regenerative braking systems in
locomotives
By: Mostafa W. Alzahlan
For example Jaipur Metro uses the Regenerative
Braking System & saves 35% of Electricity.
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Regenerative braking systems in
cars
 Toyota Prius
 Honda Insight
 Ford Escape Hybrid
 Tesla Roadster
 Chevy Volt
By: Mostafa W. Alzahlan
For example the following cars contain
regenerative braking systems
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By: Mostafa W. Alzahlan
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Circuit diagram of regenerative braking system in hybrid car
Increase of overall energy efficiency of a vehicle.
Improved Performance.
Emission Reduction.
Reduction in Engine Wear.
Cuts down on pollution related to electricity
generation.
• Increases the lifespan of friction braking systems.
• Smaller Accessories.
• Less use of traditional mechanical brakes leads to
less wear over time.
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By: Mostafa W. Alzahlan
Advantages of regenerative
braking system
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 Added Weight-Extra components can increase
weight.
 Complexity-depends on control necessary for
operation of regenerative braking system.
 Cost of components, engineering, manufacturing
and installation is high.
 Friction brakes are still necessary.
 Safety-Primary concern with any energy storage
unit of high energy density.
 Added maintenance requirements dependent on
the complexity of design.
By: Mostafa W. Alzahlan
Disadvantages of regenerative
braking system
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By: Mostafa W. Alzahlan
Dynamic (Rheostatic)
Braking system
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• The energies involved in stopping high speed trains
are so great that disc brakes alone are unsuitable
because of their very high wear rates and consequent
maintenance costs. Whenever possible, regenerative
braking is used. In this case the drive motors convert
the kinetic energy of the train into electricity, which is
fed back into the power supply and used elsewhere on
the network. Alternatively the same regenerated
electricity may be dissipated as heat in on-board or
trackside resistive (or rheostatic) brakes.
• This is an effective and easy to control braking
method. Rheostatic brakes are non-wearing and
unlike regenerative braking systems are totally
independent of the external network conditions.
By: Mostafa W. Alzahlan
Dynamic (Rheostatic) braking
System
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• The rheostatic (dynamic) braking system use the
electric traction motors of a vehicle as generators
when slowing. But instead of stored the generated
electrical energy its dissipated as heat by a bank
of onboard resistors or "braking grid". Large
cooling fans are necessary to protect the resistors
from damage. Modern systems have thermal
monitoring and when the temperature of the bank
becomes excessive, it is switched off and the
system employs only friction braking.
By: Mostafa W. Alzahlan
Principle of operation of
dynamic braking
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• Why to use the rheostatic resistor? What are
the benefits?
• In order to dissipate the excess voltage as a
heat.
• To minimize the wear and tear of friction
braking components.
• Enable faster braking.
• Eliminate the risk of a runaway due to
overheating.
By: Mostafa W. Alzahlan
Rheostatic (Dynamic) resistor
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• Braking resistors with smaller ohmic values
will help motors stop faster but will also
dissipate more heat. This will require the use
of more mass in the resistor or a heat sink to
keep its temperature within a safe limit.
By: Mostafa W. Alzahlan
Rheostatic (Dynamic) resistor
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The two types of crowbar resistor, hard and soft,
are both used in traction power supply circuits
to deal with the effects of transient or longer
lasting over-voltage conditions. The soft
crowbar is pulsed to dissipate transient overvoltages; if these persist or worsen then the
main breakers are opened and the system is
short-circuited through the hard crowbar to
absorb the stored energy
By: Mostafa W. Alzahlan
Crow bar (Rheostatic) resistors
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Dynamic Braking Resistor
Crow bar resistors
By: Mostafa W. Alzahlan
Dynamic Braking Resistor
inside a NEMA 1 enclosure
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• Rheostatic Braking (Hitachi train).
• Rheostatic Brake (Comeng train).
• DC motor braking using rheostatic
braking.
• Dynamic (Rheostatic) braking of
induction motor.
By: Mostafa W. Alzahlan
Applications of dynamic
(rheostatic) braking system
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By: Mostafa W. Alzahlan
Rheostatic Braking
(Hitachi train)
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Simple wiring diagram for traction motor
By: Mostafa W. Alzahlan
Traction motor under rheostatic braking mode. (Hitachi train)
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By: Mostafa W. Alzahlan
Rheostatic Brake
(Comeng train)
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Direct-current motors are extensively used in variablespeed drives and position-control systems where good
dynamic response and steady-state performance are
required.
For example in application of robotic drives, printers,
machine tools, process rolling mills, paper and textile
industries, and many others. Control of a dc motor,
especially of the separately excited type, is very
straightforward, mainly because of the incorporation of
the commutator within the motor.
The commutator brush allows the motor-developed
torque to be proportional to the armature current if the
field current is held constant. Classical control theories
are then easily applied to the design of the torque and
other control loops of a drive system.
By: Mostafa W. Alzahlan
DC motor braking using
rheostatic braking
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By: Mostafa W. Alzahlan
DC motor braking using
rheostatic braking
Dynamic braking in separately excited DC motor
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By: Mostafa W. Alzahlan
DC motor braking using
rheostatic braking
Dynamic Braking Speed-Torque characteristics of
separately excited DC motor with variable RD
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By: Mostafa W. Alzahlan
DC motor braking using
rheostatic braking
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Dynamic Braking of DC Motor
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By: Mostafa W. Alzahlan
extensively increasing because of their high robustness,
reliability, low cost, high efficiency and good self-starting
capability. For the use of industrial applications one of the most
important control parameter in the motor drive system is
braking. There is a need to bring a drive system quickly to rest
to hold a drive at standstill after some operation has been
completed, or under the condition of faulty operation to save
the machinery parts or operating personal. Basically, the
braking system for electric motor fundamental is one
mechanism to create retarding torque to stop the motor
rotation with sudden or slow stop depending on application in
the system. In other word, braking is essentially the removal of
stored kinetic energy from a mechanical part of the system. One
of the most effective way to brake the induction motor is to use
the dynamic (rheostatic) braking.
By: Mostafa W. Alzahlan
Dynamic (Rheostatic) braking
of
induction
motor
In many industrial applications the use of induction motor is
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Four types of dynamic (rheostatic)
braking could be applied on the induction
motor to be braked:
• AC dynamic braking.
• Self-Excited braking using capacitor.
• DC dynamic braking.
• Zero-Sequence braking.
By: Mostafa W. Alzahlan
Dynamic (Rheostatic) braking
of induction motor
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By: Mostafa W. Alzahlan
Capacitor Self-excitation
braking
Capacitor braking
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By: Mostafa W. Alzahlan
DC injection braking
DC injection braking
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By: Mostafa W. Alzahlan
Magnetic braking
Magnetic braking
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By: Mostafa W. Alzahlan
Zero-Sequence Dynamic Braking
Zero-sequence braking
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By: Mostafa W. Alzahlan
Countercurrent
Braking System
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Countercurrent (reverse current) braking system is an
electric braking achieved by switching the power supplied
to the windings of an actuating motor in such a way that
the direction of the tractive force is reversed. This
reversal can be obtained either by changing the polarity
of the voltage connected to the winding of the rotating
armature of the motor or by switching two phases of the
stator winding.
The magnitude of the braking torque can be regulated by
adjusting a resistance in the armature circuit. When
reverse-current braking is applied, the power feed must
be immediately disconnected from the power supply
network after every shutoff of the electric drive in order
to prevent the actuating motor from reversing its motion.
By: Mostafa W. Alzahlan
Countercurrent (Reverse
current) breaking
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• Hoisting
• Conveying machines.
• Rolling machine.
• Roller conveyers.
• Braking of DC motors
• Braking of induction motors
By: Mostafa W. Alzahlan
Applications of countercurrent
braking system
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By: Mostafa W. Alzahlan
Braking of DC motor
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By: Mostafa W. Alzahlan
Braking of DC motor
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Plugging of DC motor
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By: Mostafa W. Alzahlan
Plugging is one of the electrical braking methods applicable in induction motor. The
principle of traditional plug braking, is that changing the direction of revolving
magnetic field to oppose the direction of former magnetic field by changing the
phase sequence of three-phase voltages supply to the stator windings, and then the
motor will be brought to a halt by opposing torque in a short time. As the rotor
always tries to catch up with the rotating field, it can be reversed rapidly simply by
interchanging any two of the supply leads. If the leads on the stator windings are
reversed suddenly, the direction of rotation of the stator field is reversed. The
resulting slip is larger than one. The motor will come to an abrupt stop. Very rapid
reversal is possible using plugging but large cage motors can only be plugged if the
supply can withstand the very high currents involved, which are even larger than
when starting from rest. Frequent plugging will also cause serious overheating,
because each reversal involves the “dumping” of four times the stored kinetic energy
as heat in the windings. Moreover, there is a possibility of reversing the rotation of
motor if it fails to remove the braking as soon as the motor speed reached to zero
rpm.
By: Mostafa W. Alzahlan
Countercurrent braking of
induction motor
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By: Mostafa W. Alzahlan
Countercurrent braking of
induction motor
Plugging Braking of induction motor
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By: Mostafa W. Alzahlan
Countercurrent braking of
induction motor
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Plugging speed –torque curves of induction motor
Dynamic brakes ("rheostatic brakes" in the UK), unlike
regenerative brakes, dissipate the electric energy as heat
by passing the current through large banks of variable
resistors. Vehicles that use dynamic brakes include
forklifts, Diesel-electric locomotives, and streetcars. This
heat can be used to warm the vehicle interior, or
dissipated externally by large radiator-like cowls to house
the resistor banks.
The main disadvantage of regenerative brakes when
compared with dynamic brakes is the need to closely
match the generated current with the supply
characteristics and increased maintenance cost of the
lines. With DC supplies, this requires that the voltage be
closely controlled.
By: Mostafa W. Alzahlan
Dynamic vs. Regenerative
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Only with the development of power electronics has this
been possible with AC supplies, where the supply
frequency must also be matched (this mainly applies to
locomotives where an AC supply is rectified for DC
motors).
A small number of mountain railways have used 3phase power supplies and 3- phase induction motors.
This results in a near constant speed for all trains as the
motors rotate with the supply frequency both when
motoring and braking.
By: Mostafa W. Alzahlan
Dynamic vs. Regenerative
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• The regenerative braking effect drops off at lower speeds;
therefore the friction brake is still required in order to bring the
vehicle to a complete halt. Physical locking of the rotor is also
required to prevent vehicles from rolling down hills.
• The friction brake is a necessary back-up in the event of failure
of the regenerative brake.
• Most road vehicles with regenerative braking only have power
on some wheels (as in a two-wheel drive car) and regenerative
braking power only applies to such wheels, so in order to
provide controlled braking under difficult conditions (such as in
wet roads) friction based braking is necessary on the other
wheels.
• The amount of electrical energy capable of dissipation is limited
by either the capacity of the supply system to absorb this energy
or on the state of charge of the battery or capacitors.
By: Mostafa W. Alzahlan
Assisting regenerative braking
with frictional braking why??
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• No regenerative braking effect can occur if another
electrical component on the same supply system is not
currently drawing power and if the battery or capacitors
are already charged. For this reason, it is normal to also
incorporate dynamic braking to absorb the excess energy.
• Under emergency braking it is desirable that the braking
force exerted be the maximum allowed by the friction
between the wheels and the surface without slipping, over
the entire speed range from the vehicle's maximum speed
down to zero. The maximum force available for
acceleration is typically much less than this except in the
case of extreme high-performance vehicles. Therefore, the
power required to be dissipated by the braking system
under emergency braking conditions may be many times
the maximum power which is delivered under acceleration.
By: Mostafa W. Alzahlan
Assisting regenerative braking
with frictional braking why??
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Any Questions ??
By: Mostafa W. Alzahlan
Thank You For
Listening
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