Machine
Content
MACHINE: “A device consisting of fixed and moving parts that modifies mechanical energy and transmits it in a more useful form, known as a machine” OR “A simple device, such as a lever, a pulley, or an inclined plane that alters the magnitude or direction, or both, of an applied force; a simple machine” OR “Device that amplifies or replaces human or animal effort to accomplish a physical task.” OR “A device consisting of two or more parts that transmit or modify force and motion in order to do work”
BACKGROUND OR HISTORY: Arrangement of moving and stationary mechanical parts used to perform some useful work or to provide transportation. rom a historical perspective, many of the first machines were the result of human efforts to improve war!making capabilities; the term engineer at one time had an exclusively military connotation. "n the #nited $tates the original colonies were not permitted to make or import machine tools; it was only after the %evolution that the first manufacturing machines were built &c.'()*+ by $amuel $later for a textile mill in ,awtucket, %.". ELECTRICAL MACHINE: “An Electrical machine is the generic name for a device that converts mechanical energy to electrical energy, converts electrical energy to mechanical energy, or changes alternating current from one voltage level to a different voltage level.” CATEGORIES: -lectrical machines as employed in industry fall into three categories according to how they convert energy. 1 GENERATOR: “.enerators convert mechanical energy to electrical energy” • A/ generators • D/ generators E!"LAIN: • A generator forces electrons to flow through an external electrical circuit. "t is somewhat analogous to a water pump, which creates a flow of water but does not create the water inside. 0he source of mechanical energy, the prime mover, may be a reciprocating or turbine steam engine, water falling through a
•
turbine or waterwheel, an internal combustion engine, a wind turbine, a hand crank, compressed air or any other source of mechanical energy. 0here are two main parts of a generator which can be described in either mechanical or electrical terms. "n mechanical terms the r#t#r is the rotating part of an electrical machine, and the $tat#r is the stationary part of an electrical machine. "n electrical terms the armature is the power!producing component of an electrical machine and the field is the magnetic field component of an electrical machine. 0he armature can be on either the rotor or the stator. 0he magnetic field can be provided by either electromagnets or permanent magnets mounted on either the rotor or the stator. .enerators are classified into two types, A/ generators and D/ generators.
AC GENERATOR:
• An A/ generator converts mechanical energy into alternating current electricity.
1ecause power transferred into the field circuit is much less than power transferred into the armature circuit, A/ generators nearly always have the field winding on the
rotor and the armature winding on the stator.
•
A/ generators are classified into several types. 0he first is asynchronous or induction generators, in which stator flux induces currents in the rotor. 0he prime mover then
drives the rotor above the synchronous speed, causing the opposing rotor flux to cut the stator coils producing active current in the stator coils, thus sending power back to the electrical grid. 0he second type is synchronous generators or alternator, in which the current for the magnetic field is provided by a separate D/ current source.
DC GENERATOR:
A D/ generator produces direct current electrical power from mechanical energy. A D/ generator can operate at any speed within mechanical limits and always output a direct current waveform. Direct current generators known as dynamos work on exactly the same principles as alternators, but have a commutator on the rotating shaft which converts the alternating current produced by the armature to direct current.
% MOTOR: “2otors convert electrical energy to mechanical energy” • A/ motor • D/ motor E!"LAIN: • 0he reverse process of electrical generators, most electric motors operate through interacting magnetic fields and current!carrying conductors to generate rotational force. 2otors and generators have many similarities and many types of electric motors can be run as generators, and vice versa. • -lectric motors are found in applications as diverse as industrial fans, blowers and pumps, machine tools, household appliances, power tools, and disk drives. 0hey may be powered by direct current or by alternating current which leads to the two main classifications3 A/ motors and D/ motors.
AC MOTOR:
• An A/ motor converts alternating current into mechanical energy. "t commonly consists of two basic parts, an outside stationary stator having coils supplied with alternating current to produce a rotating magnetic field, and an inside rotor attached to the output shaft that is given a tor4ue by the rotating field. 0here are two main types of A/ motors, depending on the type of rotor used. 0he first type is the induction motor, which only runs slightly slower or faster than the supply fre4uency. 0he magnetic field on the rotor of this motor is created by an induced current. 0he second type is the synchronous motor, which does not rely on induction and as a result, can rotate exactly at the supply fre4uency or a sub!multiple of the supply fre4uency. 0he magnetic field on the rotor is either generated by current delivered through slip rings or by a permanent magnet.
•
DC MOTOR: • 0he brushed D/ electric motor generates tor4ue directly from D/ power supplied to the motor by using internal commutation, stationary permanent magnets, and rotating electrical magnets. 1rushes and springs carry the electric current from the commutator to the spinning wire windings of the rotor inside the motor. 1rushless D/ motors use a rotating permanent magnet in the rotor, and stationary electrical magnets on the motor housing. A motor controller converts D/ to A/. 0his design is simpler than that of brushed motors because it eliminates the complication of transferring power from outside the motor to the spinning rotor. An example of a brushless, synchronous D/ motor is a stepper motor which can divide a full rotation into a large number of steps. 0he motor5s position can be controlled precisely without any feedback mechanism as long as the motor is carefully si6ed to the application.
•
COM"ARISON DIAGRAM O& GENERATOR AND MOTOR: rom below diagram we can easily understand difference between generator and a motor
' TRANS&ORMER: “0ransformer change the voltage of alternating current” '. $0-, #, 0%A7$ 8%2-% 9. $0-, D8:7 0%A7$ 8%2-% E!"LAIN: •
A transformer is a static device that converts alternating current from one voltage level to another level &higher or lower+, or to the same level, without changing the fre4uency. A transformer transfers electrical energy from one circuit to another through inductively coupled conductors;the transformer5s coils. A varying electric current in the first or primary winding creates a varying magnetic flux in the transformer5s core and thus a varying magnetic field through the secondary winding. 0his varying magnetic field induces a varying electromotive force &-2 + or <voltage< in the secondary winding. 0his effect is called mutual induction.
STE" U" TRANS&ORMER
STE" DO(N TRANS&ORMER
&URTHER TY"ES O& MACHINE: '. -lectromagnetic!rotor machines 9. ,ermanent magnet machines =. 1rushed machines >. "nduction machines ?. %eluctance machines @. -lectrostatic machines (. Aomopolar machines B. $ynchronous machines ). Asynchronous machines '*. Aydraulics machines ''. stepper machines
E!"LAIN &RINGING E&&ECT AND HO( IT CAN BE REDUCE::::: &RINGING E&&ECT: “, the magnetic flux in the air gap of electrical machines is reduced. 0his leads to the larger -ffective air gap length,so flux leackage occurred. or this reason, in the design stage of the electrical machines, a larger magnetic flux must be chosen. 8n the other hand, magnetic loading must be taken smaller than the value corresponding to the real air gap length”
HO( IT CAN BE MINIMI)E: "f the air gap is enclosed by a coil, flux fringing is reduced because of the magneti6ing force set up near the gap by the ampere!turns of the coil. A coil fitting tightly all around the core would produce no fringing at all. As the distance from inside of the coil to the core increases, so does the fringing. ringing therefore depends upon the coil form thickness; if it materially exceeds the air gap per leg, fringing is nearly the same as it would be in a core gap which is not enclosed by a coil. "ts basically a thick coil.
A "RACTICAL E!AM"LE*in telec#mm+nicati#n, TO MINIMI)E THE AIR GA"": Hi-h E..icienc/ CLL Re$#nant C#n0erter 1ith S/nchr#n#+$ Recti.ier::
0he /CC resonant dc!dc converter &/CC+ is an alternative option in off!line applications. 0his topology can achieve 6ero!voltage!switching &DE$+ from 6ero load to full load range, low circulating energy and 6ero!current!switching &D/$+ for output rectifiers. 0he air gap of the /CC resonant converter transformer is omitted to eliminate fringing effect. 1ecause of very high magneti6ing inductance, the transformer primary side current is in phase with the secondary side current. 0hus, $% can be easily driven. 2oreover, resonant inductance is integrated with the transformer to reduce the passive component volume.
&i-+re 1 Circ+it #. LLC re$#nant c#n0erter
&i-+re % Circ+it #. CLL re$#nant c#n0erter
&i-+re ' LLC tran$.#rmer 12 -a3 *$e0ere .rin-ine..ect,
&i-+re 4 CLL &i-+re 5 "rimar/ an6 tran$.#rmer 12# -a3 Sec#n6ar/ c+rrent #. &i-+re 7 (a0e.#rm$ #. CLL LLC tran$.#rmer *#+t #. c+rrent 6ri0en SR *little .rin-in- e..ect, 3ha$e,
REFFERENCES::::::::::: • • • • • :::.A7$:-%./82 :::..88.C-./82 :::.:"F",-D"A./82 188F$ 2A0-%"AC "--- ,A,-%$
BACKGROUND OR HISTORY: Arrangement of moving and stationary mechanical parts used to perform some useful work or to provide transportation. rom a historical perspective, many of the first machines were the result of human efforts to improve war!making capabilities; the term engineer at one time had an exclusively military connotation. "n the #nited $tates the original colonies were not permitted to make or import machine tools; it was only after the %evolution that the first manufacturing machines were built &c.'()*+ by $amuel $later for a textile mill in ,awtucket, %.". ELECTRICAL MACHINE: “An Electrical machine is the generic name for a device that converts mechanical energy to electrical energy, converts electrical energy to mechanical energy, or changes alternating current from one voltage level to a different voltage level.” CATEGORIES: -lectrical machines as employed in industry fall into three categories according to how they convert energy. 1 GENERATOR: “.enerators convert mechanical energy to electrical energy” • A/ generators • D/ generators E!"LAIN: • A generator forces electrons to flow through an external electrical circuit. "t is somewhat analogous to a water pump, which creates a flow of water but does not create the water inside. 0he source of mechanical energy, the prime mover, may be a reciprocating or turbine steam engine, water falling through a
•
turbine or waterwheel, an internal combustion engine, a wind turbine, a hand crank, compressed air or any other source of mechanical energy. 0here are two main parts of a generator which can be described in either mechanical or electrical terms. "n mechanical terms the r#t#r is the rotating part of an electrical machine, and the $tat#r is the stationary part of an electrical machine. "n electrical terms the armature is the power!producing component of an electrical machine and the field is the magnetic field component of an electrical machine. 0he armature can be on either the rotor or the stator. 0he magnetic field can be provided by either electromagnets or permanent magnets mounted on either the rotor or the stator. .enerators are classified into two types, A/ generators and D/ generators.
AC GENERATOR:
• An A/ generator converts mechanical energy into alternating current electricity.
1ecause power transferred into the field circuit is much less than power transferred into the armature circuit, A/ generators nearly always have the field winding on the
rotor and the armature winding on the stator.
•
A/ generators are classified into several types. 0he first is asynchronous or induction generators, in which stator flux induces currents in the rotor. 0he prime mover then
drives the rotor above the synchronous speed, causing the opposing rotor flux to cut the stator coils producing active current in the stator coils, thus sending power back to the electrical grid. 0he second type is synchronous generators or alternator, in which the current for the magnetic field is provided by a separate D/ current source.
DC GENERATOR:
A D/ generator produces direct current electrical power from mechanical energy. A D/ generator can operate at any speed within mechanical limits and always output a direct current waveform. Direct current generators known as dynamos work on exactly the same principles as alternators, but have a commutator on the rotating shaft which converts the alternating current produced by the armature to direct current.
% MOTOR: “2otors convert electrical energy to mechanical energy” • A/ motor • D/ motor E!"LAIN: • 0he reverse process of electrical generators, most electric motors operate through interacting magnetic fields and current!carrying conductors to generate rotational force. 2otors and generators have many similarities and many types of electric motors can be run as generators, and vice versa. • -lectric motors are found in applications as diverse as industrial fans, blowers and pumps, machine tools, household appliances, power tools, and disk drives. 0hey may be powered by direct current or by alternating current which leads to the two main classifications3 A/ motors and D/ motors.
AC MOTOR:
• An A/ motor converts alternating current into mechanical energy. "t commonly consists of two basic parts, an outside stationary stator having coils supplied with alternating current to produce a rotating magnetic field, and an inside rotor attached to the output shaft that is given a tor4ue by the rotating field. 0here are two main types of A/ motors, depending on the type of rotor used. 0he first type is the induction motor, which only runs slightly slower or faster than the supply fre4uency. 0he magnetic field on the rotor of this motor is created by an induced current. 0he second type is the synchronous motor, which does not rely on induction and as a result, can rotate exactly at the supply fre4uency or a sub!multiple of the supply fre4uency. 0he magnetic field on the rotor is either generated by current delivered through slip rings or by a permanent magnet.
•
DC MOTOR: • 0he brushed D/ electric motor generates tor4ue directly from D/ power supplied to the motor by using internal commutation, stationary permanent magnets, and rotating electrical magnets. 1rushes and springs carry the electric current from the commutator to the spinning wire windings of the rotor inside the motor. 1rushless D/ motors use a rotating permanent magnet in the rotor, and stationary electrical magnets on the motor housing. A motor controller converts D/ to A/. 0his design is simpler than that of brushed motors because it eliminates the complication of transferring power from outside the motor to the spinning rotor. An example of a brushless, synchronous D/ motor is a stepper motor which can divide a full rotation into a large number of steps. 0he motor5s position can be controlled precisely without any feedback mechanism as long as the motor is carefully si6ed to the application.
•
COM"ARISON DIAGRAM O& GENERATOR AND MOTOR: rom below diagram we can easily understand difference between generator and a motor
' TRANS&ORMER: “0ransformer change the voltage of alternating current” '. $0-, #, 0%A7$ 8%2-% 9. $0-, D8:7 0%A7$ 8%2-% E!"LAIN: •
A transformer is a static device that converts alternating current from one voltage level to another level &higher or lower+, or to the same level, without changing the fre4uency. A transformer transfers electrical energy from one circuit to another through inductively coupled conductors;the transformer5s coils. A varying electric current in the first or primary winding creates a varying magnetic flux in the transformer5s core and thus a varying magnetic field through the secondary winding. 0his varying magnetic field induces a varying electromotive force &-2 + or <voltage< in the secondary winding. 0his effect is called mutual induction.
STE" U" TRANS&ORMER
STE" DO(N TRANS&ORMER
&URTHER TY"ES O& MACHINE: '. -lectromagnetic!rotor machines 9. ,ermanent magnet machines =. 1rushed machines >. "nduction machines ?. %eluctance machines @. -lectrostatic machines (. Aomopolar machines B. $ynchronous machines ). Asynchronous machines '*. Aydraulics machines ''. stepper machines
E!"LAIN &RINGING E&&ECT AND HO( IT CAN BE REDUCE::::: &RINGING E&&ECT: “, the magnetic flux in the air gap of electrical machines is reduced. 0his leads to the larger -ffective air gap length,so flux leackage occurred. or this reason, in the design stage of the electrical machines, a larger magnetic flux must be chosen. 8n the other hand, magnetic loading must be taken smaller than the value corresponding to the real air gap length”
HO( IT CAN BE MINIMI)E: "f the air gap is enclosed by a coil, flux fringing is reduced because of the magneti6ing force set up near the gap by the ampere!turns of the coil. A coil fitting tightly all around the core would produce no fringing at all. As the distance from inside of the coil to the core increases, so does the fringing. ringing therefore depends upon the coil form thickness; if it materially exceeds the air gap per leg, fringing is nearly the same as it would be in a core gap which is not enclosed by a coil. "ts basically a thick coil.
A "RACTICAL E!AM"LE*in telec#mm+nicati#n, TO MINIMI)E THE AIR GA"": Hi-h E..icienc/ CLL Re$#nant C#n0erter 1ith S/nchr#n#+$ Recti.ier::
0he /CC resonant dc!dc converter &/CC+ is an alternative option in off!line applications. 0his topology can achieve 6ero!voltage!switching &DE$+ from 6ero load to full load range, low circulating energy and 6ero!current!switching &D/$+ for output rectifiers. 0he air gap of the /CC resonant converter transformer is omitted to eliminate fringing effect. 1ecause of very high magneti6ing inductance, the transformer primary side current is in phase with the secondary side current. 0hus, $% can be easily driven. 2oreover, resonant inductance is integrated with the transformer to reduce the passive component volume.
&i-+re 1 Circ+it #. LLC re$#nant c#n0erter
&i-+re % Circ+it #. CLL re$#nant c#n0erter
&i-+re ' LLC tran$.#rmer 12 -a3 *$e0ere .rin-ine..ect,
&i-+re 4 CLL &i-+re 5 "rimar/ an6 tran$.#rmer 12# -a3 Sec#n6ar/ c+rrent #. &i-+re 7 (a0e.#rm$ #. CLL LLC tran$.#rmer *#+t #. c+rrent 6ri0en SR *little .rin-in- e..ect, 3ha$e,
REFFERENCES::::::::::: • • • • • :::.A7$:-%./82 :::..88.C-./82 :::.:"F",-D"A./82 188F$ 2A0-%"AC "--- ,A,-%$
