Download - 91948246 Regenerative Braking Ppt Final
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STVINCENT PALLOTTICOLL6 OF
ENGINRIN6AND TCHNOLOGY NAGPUR
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BRAKES
A BRAKE IS A MACHINE ELEMENT AND ITSPRINCIPLE OBJECTIVE IS TO ABSORB ENERGYDURING DECELERATION.
BY CONNECTING THE MOVING MEMBER TOSTATIONARY FRAME, NORMALLY BRAKECONVERTS KINETIC ENERGY TO HEAT ENERGY.
THIS CAUSES WASTAGE OF ENERGY AND ALSOWEARING OF FRICTIONAL LINING MATERIAL.
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DEFINITION
BRAKING METHOD IN WHICH THE MECHANICAL
ENERGY FROM THE LOAD IS CONVERTED INTO
ELECTRIC ENERGY AND REGENERATED BACK
INTO THE LINE IS KNOWN AS REGENERATIVE
BRAKING. THE MOTOR OPERATES AS GENERATOR.
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NECESSITY OF THE REGENERATIVE
BRAING SYSTEM
IN LOW-SPEED, STOP-AND-GO TRAFFIC WHERE LITTLEDECELERATION IS REQUIRED; THE REGENERATIVE BRAKINGSYSTEM CAN PROVIDE THE MAJORITY OF THE TOTAL BRAKING
FORCE. THIS VASTLY IMPROVES FUEL ECONOMY WITH AVEHICLE, AND FURTHER ENHANCES THE ATTRACTIVENESS OFVEHICLES USING REGENERATIVE BRAKING FOR CITY DRIVING.
AT HIGHER SPEEDS, TOO, REGENERATIVE BRAKING HAS BEENSHOWN TO CONTRIBUTE TO IMPROVED FUEL ECONOMY BY AS
MUCH AS 20%.
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REGENERATIVE BREAKING -
OVERVIEW
REGENERATIVE BRAKING IS USED TO
IMPROVE THE EFFICIENCY (FUEL ECONOMY)
OF:
ELECTRIC VEHICLESHYBRID VEHICLES
INDUSTRIAL APPLICATIONS
LOWERS OPERATION COST
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Batteries Motor
Brakes
Batteries MotorKineticEnergy
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WORKING
REGENERATIVE BRAKING SYSTEM IS THE WAY OF SLOWING VEHICLE BYUSING THE MOTORS AS BRAKES. INSTEAD OF THE SURPLUS ENERGY OFTHE VEHICLE BEING WASTED AS UNWANTED HEAT, THE MOTORS ACT ASGENERATORS AND RETURN SOME OF IT TO THE OVERHEAD WIRES ASELECTRICITY.
THE VEHICLE IS PRIMARILY POWERED FROM THE ELECTRICAL ENERGY
GENERATED FROM THE GENERATOR, WHICH BURNS GASOLINE. THISENERGY IS STORED IN A LARGE BATTERY, AND USED BY AN ELECTRICMOTOR THAT PROVIDES MOTIVE FORCE TO THE WHEELS.
THE REGENERATIVE BARKING TAKING PLACE ON THE VEHICLE IS A WAYTO OBTAIN MORE EFFICIENCY; INSTEAD OF CONVERTING KINETIC
ENERGY TO THERMAL ENERGY THROUGH FRICTIONAL BRAKING, THEVEHICLE CAN CONVERT A GOOD FRACTION OF ITS KINETIC ENERGY BACKINTO CHARGE IN THE BATTERY, USING THE SAME PRINCIPLE AS ANALTERNATOR.
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Elil l liiE A TU : Oti
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TYPES OF REGENERATIVE BRAKING
SYSTEM1. HYDRAULIC REGENERATIVE BRAKES
VEHICLE'S KINETIC ENERGY IS USED TO POWER A REVERSIBLE PUMP, WHICH SENDS
HYDRAULIC FLUID FROM A LOW PRESSURE ACCUMULATOR (A KIND OF STORAGE
TANK) INSIDE THE VEHICLE INTO A HIGH PRESSURE ACCUMULATOR. THE PRESSURE
IS CREATED BY NITROGEN GAS IN THE ACCUMULATOR, WHICH IS COMPRESSED AS
THE FLUID IS PUMPED INTO THE SPACE THE GAS FORMERLY OCCUPIED. THIS SLOWS
THE VEHICLE AND HELPS BRING IT TO A STOP.
2. FLY WHEELS
ROTATING PART OF THE ENGINE INCORPORATES A WHEEL WITH A VERY HEAVYMETAL RIM, AND THIS DRIVES WHATEVER MACHINE OR DEVICE THE ENGINE IS
CONNECTED TO. IT TAKES MUCH MORE TIME TO GET A FLYWHEEL-ENGINE TURNING
BUT, ONCE IT'S UP TO SPEED, THE FLYWHEEL STORES A HUGE AMOUNT OF
ROTATIONAL ENERGY.
3. USE IN COMPRESSED AIR
REGENERATIVE BRAKES COULD BE EMPLOYED IN COMPRESSED AIR CARS TO REFILL
THE AIR TANK DURING BRAKING. BY ABSORBING THE KINETIC ENERGY (NECESSARY
FOR BARKING), USING THE SAME FOR COMPRESSING THE AIR AND REUSE THESE
COMPRESSED AIR WHILE POWERING THE CAR.
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BRAKING PARAMETERS
Safe Interval Should Be > 3 seconds 6 seconds
Speed Distance Travelled For These Conditions > Good Marginal
25 m.p.h. 37 ft. per second 111 ft. 222 ft.
35 m.p.h. 52 ft. per second 166 ft. 312 ft.
45 m.p.h. 66 ft. per second 198 ft. 396 ft.
55 m.p.h. 81 ft. per second 243ft. 486 ft.
65 m.p.h. 96 ft. per second 288 ft. 576 ft.
75 m.p.h. 111 ft. per second 333 ft. 666 ft.
Safe Following Distance in Feet
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Regenerative Brakes Try To Slow Down The Vehicle And It Is Quite Difficult
To Bring It To Complete Halt.
In Cities Many A Times There Is Necessity To Bring The Vehicle To Complete Halt
Suddenly Due To Heavy Traffic
In Such Situation Use Of Regenerative Brakes Alone Is Dangerous
To Overcome This Issue Regenerative Braking System Is Accompanied With
Traditional Barking System.
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Traditional friction-based braking is used in conjunction with mechanical
regenerative braking for the following reasons:
The regenerative braking effect drops off at lower speeds; therefore thefriction 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 theregenerative 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 underdifficult conditions (such as in wet roads) friction based braking is
necessary on the other wheels.
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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. 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 theentire 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. Traction motors sized to handlethe drive power may not be able to cope with the extra load and the battery may not be
able to accept charge at a sufficiently high rate. Friction braking is required to absorb
the surplus energy in order to allow an acceptable emergency braking performance.
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ADVANTAGES OF REGENERATIVE
BRAKING ACCOMPANIED WITH
CONVENTIONAL BRAKING
ENERGY CONSERVATION
WEAR REDUCTION
LOW FUEL CONSUMPTION
BRAKING IS NOT TOTAL LOSS
ENHANCED SAFETY OF DRIVER
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CONCLUSION
THE BEGINNING OF THE 21ST CENTURY COULD VERY WELL MARK THE FINAL
PERIOD IN WHICH INTERNAL COMBUSTION ENGINES ARE COMMONLY USED
IN CARS.
ALREADY AUTOMAKERS ARE MOVING TOWARD ALTERNATIVE ENERGYCARRIERS, SUCH AS ELECTRIC BATTERIES, HYDROGEN FUEL AND EVEN
COMPRESSED AIR.
REGENERATIVE BRAKING IS A SMALL, YET VERY IMPORTANT, STEP TOWARD
OUR EVENTUAL INDEPENDENCE FROM FOSSIL FUELS AND CAN OPEN A NEW
REALM IN SAFETY ON ROADS.
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THANK YOU...