Transcript ME 2205 ELECTRICAL DRIVES AND CONTROL

ME 2205 ELECTRICAL DRIVES
AND CONTROL
UNIT I INTRODUCTION
BY
B.DURAI BABU A.P/EEE
BASIC ELEMENTS
POWER
SUPPLY
CONTROL
EQUIPME
NT
ELECTRIC
MOTOR
MECHANICAL
LOAD
ELECTRICAL DRIVE
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A UNIT CONSITING OF AN
ELECTRICAL MOTOR
ENERGY TRANSMITTING SHAFT
CONTROL EQUIPMENT
DRIVE SYSTEM
• COMBINATION OF
• ELECTRICAL DRIVE AND CORRESPONDING
LOAD
ADVANTAGES
• FEASIBLE CONTROL CHARACTERISTICS
• AVAILABLE IN WIDE RANGE OF SPEED TORQUE
AND POWER
• HIGHER EFFICIENCY
• LOWER NOISE
• CLEANER OPERATION
• LOW MAINTENANCE REQUIREMENTS
• ELECTRIC ENERGY IS EASY TO TRANSPORT
TYPES OF ELECTRICAL DRIVES
• GROUP DRIVE
• INDIVIDUAL DRIVE
• MULTIMOTOR DRIVE
GROUP DRIVE
• DRIVE CONSISTS OF ONLY ONE ELECTRIC
MOTOR WHICH DRIVES SEVERAL MACHINES
• ADVANTAGE
• RATING OF AN ELECTRICAL DRIVE CAN BE
SMALLER
• DISADVANTAGE
• IF ELECTRIC MOTOR IS SUBJECTED TO ANY
FAULT ALL THE EQUIPMENTS BECOME IDLE
INDIVIDUAL DRIVE
• IF A SINGLE MOTOR IS USED TO DRIVE A
SINGLE MACHINE AND ALL THE MECHANISMS
BELONGING TO THE SAME MACHINE.
• DISADVANTAGE
• DUE TO POWER LOSS ,THE EFFICIENCY OF
SUCH DRIVE IS ALSO POOR
MULTIMOTOR DRIVE
• A SEPARATE MOTOR IS PROVIDED FOR
DRIVING THE SEPARATE MECHANISM
• ADVANTAGES
• INCREASE THE OVERALL PRODUCTIVITY
FACTORS AFFECTING THE SELECTION
OF DRIVE
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LIMIT OF SPEED RANGE
EFFICIENCY
BRAKING
STARTING REQUIREMENTS
POWER FACTOR
LOAD FACTOR
AVAILABILITY OF SUPPLY
ECONOMICAL ASPECTS
SELECTION OF MOTOR BASED ON
LOAD VARIATION
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CONTINOUS LOAD
CONTINOUS VARIABLE LOAD
PULSATING LOAD
IMPACT LOADS
SHORT TIME INTERMITTENT LOAD
SHORT TIME LOAD
CLASSES OF DUTY AND SELECTION OF
RATING OF MOTOR
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ONCE CYCLE OF VARIATION OF LOAD IS DUTY
CONTINOUS DUTY
CONTINOUS DUTY,VARIABLE LOAD
SHORT TIME DUTY
INTERMITTENT PERIODIC DUTY
INTERMITTENT PERIODIC DUTY WITH STARTING
INTERMITTENT PERIODIC DUTY WITH STARTING
AND BRAKING
POWER LOSSES AND HEATING OF
MOTOR
• COPPER LOSS
• CORE LOSS
• POWER LOSSES CAUSE LOCALISED HEATING
AND RESPONSIBLE FOR TEMPERATURE RISE
OF THE MOTOR
STEADY STATE CONDITION
• FINAL TEMPERATURE RISE IS REACHED WHEN
THE RATE OF PRODUCTION OF HEAT AND
RATE OF HEAT DISSIPATION ARE EQUAL
CONTINOUS RATING
• CONTINOUS RATING OF A MACHINE IS THAT
RATING FOR WHICH THE TEMPERATURE RISE
IS JUST BELOW THE PERMISSIBLE VALUE OF
TEMPERATURE RISE
HEATING AND COOLING CURVES
• A SMALLER TIME CONSTANT IS OBTAINED FOR
GOOD VENTILATION
• THE TIME CONSTANT IS INVERSELY
PROPORTIONAL TO SPECIFIC HEAT
DISSIPATION
• COOLING TIME CONSTANT IS THE TIME
REQUIRED TO COOL THE MACHINE
SELECTION OF POWER RATING FOR
DRIVE MOTORS
• CONTINOUS LOAD
• CONTINOUS RATING SPECIFIES THE
MAXIMUM LOAD THAT THE MOTOR CAN TAKE
OVER A PERIOD FOR TIME
• CONTINOUS VARIABLE LOAD
• CLASS OF DUTY IS SELECTED ON BASED ON
AVERAGE POWER OR CURRENT
SELECTION OF MOTOR FOR
INDUSTRIAL APPLICATIONS
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STEEL ROLLING MILLS
DC MOTOR WITH WARD LEONARD SYSTEM
AC COMMUTATOR MOTORS
ACCURATE TORQUE AND SPEED CONTROL
CRANES AND HOISTS
• SERIES MOTORS
• GOOD STARTING TORQUE
• ELECTRIC BRAKING AT LOW SPEED IS POSSIBLE
TEXTILE INDUSTRY
• MODERATE STARTING TORQUE
• CONSTANT SPEED
• HIGH TORQUE SQUIRREL CAGE INDUCTION
MOTOR IS PREFFERED
COAL AND MINNING INDUSTRY
• COAL CUTTING OR DRILLING REQUIRES
COSTANT SPEED AND HIGH STARTING TORQUE
• SQUIRREL CAGE MOTORS ARE PREFFERED
• CENTRIFUGAL PUMPS ARE USED IN MINNING
FOR PUMPING WATER.
• HIGH TORQUE SQUIRREL CAGE ARE SELECTED
IMPORTANT QUESTIONS -TWO MARKS
• DRAW THE FUNCTIONAL FUNCTIONAL
DIAGRAM OF AN ELECTRICAL DRIVE SYSTEM
• GIVE ANY TWO FACTORS THAT INFLUENCE THE
CHOICE OF ELECTRICAL DRIVES
• MENTION THE USAGE OF DIFFERENT TYPES OF
MOTORS WITH APPLICATION IN TEXTILE MILL
• WHAT IS MEANT INTERMITTENT DUTY
• LIST ANY FOUR ADVANTAGES OF ELECTRIC
DRIVES
IMPORTANT QUESTIONS -TWO MARKS
• WHAT IS MEANT BY ELECTRIC DRIVE
• DEFINE CONTINOUS RATING OF A MOTOR
• WHAT IS OVERLOAD CURRENT CAPABILITY OF
MOTOR
• DEFINE COOLING TIME CONSTANT OF A
MACHINE
• NAME ANY FOUR CLASSES OF DUTY
IMPORTANT QUESTIONS -SIXTEEN
MARKS
• DERIVE AN EXPRESSION FOR A THERMAL
MODEL OF MOTOR FOR HEATING AND
COOLING.ALSO DRAW THE HEATING AND
COOLING CURVE
• EXPLAIN THE DIFFERENT CLASSES OF MOTOR
DUTY WITH NEAT SKETCH
• EXPLAIN THE VARIOUS FACTORS INFLUENCING
THE CHOICE OF ELECTRICAL DRIVE
IMPORTANT QUESTIONS -SIXTEEN
MARKS
• PROBLEMS DISCUSSED IN THE CLASS
COMPARISON BETWEEN AC AND DC
DRIVE
S.NO
D.C.DRIVE
A.C DRIVE
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SPEED TORQUE CAN BE ACHIEVED EASILY
IT IS NOT EASTY TO ADJUST
SPEED TORQUE CURVES
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SELF STARTING
NOT SELF STARTING
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FREQUENT MAINTENANCE IS REQUIRED
LESS MAINTENANCE
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COSTLY
CHEAPER
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RECTIFYING CIRCUIT IS NECESSARY
NO NEED
FOUR QUADRANT OPERATION
QUADRAN POLARITY OF
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VOLTAGE
POLARITY OF
CURRENT
NATURE OF OPERATION
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POSITIVE
POSITIVE
FORWARD MOTORING
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POSITIVE
NEGATIVE
FORWARD REGENERATION
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NEGATIVE
NEGATIVE
REVERSE MOTORING
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NEGATIVE
POSITIVE
REVERSE REGENERATION