BEEE Unit 3 PPT Electrical Machines PDF

Unit III ELECTRICAL MACHINES December 3, 2024 Department of EECE, GIT Course Code and Course Title:19EEE131-BEEE 1  Unit-III ELECTRICAL MACHINES...

Unit III ELECTRICAL MACHINES December 3, 2024 Department of EECE, GIT Course Code and Course Title:19EEE131-BEEE 1  Unit-III ELECTRICAL MACHINES GITA Construction, working principle and application of M Deemed to be University  DC machines  Transformers  Single phase Induction motors  Tree phase Induction motors  Special machines  Stepper motor  Servo motor  BLDC motor December 3, 2024 Department of EECE, GIT Course Code and Course Title:19EEE131-BEEE 2 Magnetic Field Sources  Solenoid Department of EECE, GIT Course 12/03/2024 5 Code and Course Title:19EEE131- BEEE Electromagnet  Department of EECE, GIT Course 12/03/2024 7 Code and Course Title:19EEE131- BEEE  Department of EECE, GIT Course 12/03/2024 8 Code and Course Title:19EEE131- BEEE  Faraday’s Law of Electromagnetic Induction Faraday found that the electromotive force (EMF) produced around a closed path is proportional to the rate of change of the magnetic flux through any surface bounded by that path. In practice, this means that an electrical current will be induced in any closed circuit when the magnetic flux through a surface bounded by the conductor changes. This applies whether the field itself changes in strength or the conductor is moved through it. Electromagnetic induction underlies the operation of generators, all electric motors, transformers, induction motors, synchronous motors, solenoids, and most other electrical machines. Faraday's law of electromagnetic induction states that: E is the electromotive force (emf) in volts ΦB is the magnetic flux in Weber's N is the number of turns of wire Department of EECE, GIT Course 12/03/2024 9 Code and Course Title:19EEE131- BEEE Faradays laws of Electromagnetic Induction  Whenever there is a change in the number of field lines passing through a loop of wire a voltage (emf) is induced (generated). The magnitude of the emf induced in a conducting loop is equal to the rate at which the magnetic flux through the loop changes with time  Faradays laws of Electromagnetic Induction Faraday's law of electromagnetic induction: (i) Whenever there is a change in magnetic flux linked with a closed coil, an induced e.m.f. produced and current flows through the coil. This induced e.m.f. remains till the flux changes. (ii) The induced e.m.f. is directly proportional to the rate of change of flux. Department of EECE, GIT Course 12/03/2024 12 Code and Course Title:19EEE131- BEEE  Faradays laws of Electromagnetic Induction Expression for induced e.m.f.: Let at any instant, the flux linked with a circuit changes from Φ1​to Φ2 in t second. Rate of change of flux =(Φ2​−Φ1​​)/t or Induced e.m.f., e ∝ −(Φ2​−Φ1​​)/t ∴e = −(Φ2​−Φ1​​)/t or e = −dΦ​/dt The negative sign shows that induced e.m.f. opposes the change of flux. Department of EECE, GIT Course 12/03/2024 13 Code and Course Title:19EEE131- BEEE  Lenz ‘s law law, in Lenz’s electromagnetism, statement that an induced electric current flows in a direction such that the current opposes the change that induced "Russian physicist it. (1804-1865) 1834 Lenz’s Law "An induced current is always in such a direction as to oppose the motion or change DC GENERATOR December 3, 2024 Department of EECE, GIT Course Co 15 de and Course Title:19EEE231- Electric circuit analysis  Department of EECE, GIT Course 12/03/2024 16 Code and Course Title:19EEE131- BEEE DC Generator Principle of Operation 17 When the plane of the coil is at right angles to lines of flux., when it is in position 1, then flux linked with the coil is maximum but rate of change of flux linkages is minimum. Hence there is no induced emf in the coil. As the coil continues rotating further the rate of change of fluz linkages increases and hence emf increase till position 3 is reached. In the next quarter revolution from 900 to 1800 , the rate of 18 AC Generator Output  Department of EECE, GIT Course 12/03/2024 20 Code and Course Title:19EEE131- BEEE  Commutator and Brushes Department of EECE, GIT Course 12/03/2024 21 Code and Course Title:19EEE131- BEEE  ACTION OF COMMUTATOR 22  Construction of DC Machines Parts of DC Machines Yoke Pole Armature Commutator Brushes Bearings Department of EECE, GIT Course 12/03/2024 23 Code and Course Title:19EEE131- BEEE  Yoke Mechanical support for poles & inter-poles Carries magnetic flux produced by the poles Protection cover for whole machine Made of cast steel Department of EECE, GIT Course 12/03/2024 24 Code and Course Title:19EEE131- BEEE  Pole shoe & Pole core Pole core : Support to the field winding ; laminated core Pole Shoe : Spread out the flux in the air gap : Reduce reluctance of magnetic path ; Made up of Cast steel /cast iron laminations Department of EECE, GIT Course 12/03/2024 25 Code and Course Title:19EEE131- BEEE  Pole Coils /Field Coils Copper wires /strips wound for the correct dimensions Produce necessary flux when excitation /current is given Department of EECE, GIT Course 12/03/2024 26 Code and Course Title:19EEE131- BEEE Field Winding Pole Shoe Department of EECE, GIT Course Code and Course 12/03/2024 Title:19EEE131- BEEE 27  Department of EECE, GIT Course Code and Course 12/03/2024 Title:19EEE131- BEEE 28  Armature of a DC Motor The center rotating part of the motor is called the “Armature Consists of Laminated core and Winding Thinner laminations : 0.4 -0.5 mm thick : High resistance ; small current ;less I^2 R loss Air Ducts : Cooling Department of EECE, GIT Course 12/03/2024 Key way :Self locking of Code and Course Title:19EEE131- BEEE 29  Armature Winding Slots are punched to core to provide conductors ,these slots are rectangular in shape Copper windings fill the slots in the iron core of the armature Coil Winding s should be in such a way to improve the mechanical ,thermal ,electrical strength of the machine – improves service life of the machine Small m/c coil : “ Enameled Copper Wire” large m/c coil : “ Double cotton covered copper wire”  Coils are Baked - to improve firmness and Dielectric Strength.  Coils are placed such that one side is under N-pole and the other is under S- pole.  Wood/Fiber used to hold the coils in slots Department of EECE, GIT Course 12/03/2024 30 Code and Course Title:19EEE131- BEEE  Armature with slots Department of EECE, GIT Course 12/03/2024 31 Code and Course Title:19EEE131- BEEE  Armature with coils Department of EECE, GIT Course 12/03/2024 32 Code and Course Title:19EEE131- BEEE  Department of EECE, GIT Course 12/03/2024 33 Code and Course Title:19EEE131- BEEE  Commutator Converts Bi-directional current to Uni-directional current Collection of current from armature Cylindrical assembly of wedge shaped copper segments insulated from one another and with the shaft by thin mica /macanite sheets. Segments are connected to armature winding through Risers /comutator lugs. Risers have ‘V’ grooves. Department of EECE, GIT Course 12/03/2024 34 Code and Course Title:19EEE131- BEEE  Department of EECE, GIT Course 12/03/2024 35 Code and Course Title:19EEE131- BEEE  Department of EECE, GIT Course 12/03/2024 36 Code and Course Title:19EEE131- BEEE  Brushes Collect current from Commutator Rectangle shape Material – carbon /graphite Housed in brush holder Department of EECE, GIT Course 12/03/2024 37 Code and Course Title:19EEE131- BEEE  Department of EECE, GIT Course 12/03/2024 38 Code and Course Title:19EEE131- BEEE  Department of EECE, GIT Course 12/03/2024 39 Code and Course Title:19EEE131- BEEE  Department of EECE, GIT Course 12/03/2024 40 Code and Course Title:19EEE131- BEEE  Department of EECE, GIT Course 12/03/2024 41 Code and Course Title:19EEE131- BEEE  Classification of DC Machines DC The classification of DC machines is according Machine to the ways of excitation of their fields. s Self Excited Separate ly Excited Series Compou Shunt nd Long Short Shunt Shunt Department of EECE, GIT Course 12/03/2024 42 Code and Course Title:19EEE131- BEEE  Symbolic representation of parts of machine brush Department of EECE, GIT Course 12/03/2024 43 Code and Course Title:19EEE131- BEEE  SEPARATELY EXCITED DC GENERATOR In separately excited dc machines, the field winding is supplied from a separate power source. The field winding is electrically separated from the armature circuit. The flux produced by the poles depends upon the field current with the unsaturated region of magnetic material of the poles. i.e. flux is directly proportional to the field current. Department of EECE, GIT Course 12/03/2024 44 Code and Course Title:19EEE131- BEEE  SELF EXCITED DC GENERATOR Self-excited DC Generator in which the current to the field winding is supplied by the generator itself. In self-excited DC generator, the field coils may be connected in parallel with the armature in the series, or it may be connected partly in series and partly in parallel with the armature windings. Department of EECE, GIT Course 12/03/2024 45 Code and Course Title:19EEE131- BEEE  DC SHUNT GENERATOR  Field winding is connected in parallel with the armature winding.  Shunt winding is made with a large number of turns and the resistance is kept very high  The full voltage is applied across the field winding.  Field winding takes current which is less than 5% of the rated armature current. Department of EECE, GIT Course 12/03/2024 46 Code and Course Title:19EEE131- BEEE  DC SERIES GENERATOR  Field winding is connected in series with the armature winding.  Series winding is designed with few turns of thick wire and the resistance is kept very low.  Field winding carries whole load current (armature current). Department of EECE, GIT Course 12/03/2024 47 Code and Course Title:19EEE131- BEEE  DC COMPOUND GENERATOR Short Shunt Long Shunt field winding is connected in parallel with field winding is connected in parallel with the only the armature winding combination of series field winding and armature winding Department of EECE, GIT Course 12/03/2024 48 Code and Course Title:19EEE131- BEEE  Applications of DC Generators Because of their ability of giving wide range of voltage output, they are generally used for testing purpose in the laboratories. They are used for general lighting. They are used to charge battery because they can be made to give constant output voltage. They are used for giving the excitation to the alternators. They are also used for small power supply. This types of generators are used as boosters to compensate the voltage drop in the feeder in various types of distribution systems such as railway service. Used for small distance operation, such as power supply for hotels, offices, homes and lodges, DC MOTOR December 3, 2024 Department of EECE, GIT Course Co 50 de and Course Title:19EEE231- Electric circuit analysis Working Principle of DC Motor A motor is an electrical machine which converts electrical energy into mechanical energy. The principle of working of a DC motor is that "whenever a current carrying conductor is placed in a magnetic field, it experiences a mechanical force.  The very basic construction of a DC motor contains a current carrying armature, connected to the supply end through commutator segments and brushes. The armature is placed in between north pole and south pole of a permanent or an electromagnet When direct current is applied in the armature, a mechanical force acts on it due to the electromagnetic effect of the magnet on armature conductors. If a current carrying conductor is placed in a magnetic field perpendicularly, then the conductor experiences a force in the direction mutually perpendicular to both the direction of field and the current carrying conductor. December 3, 2024 Department of EECE, GIT Course Co 52 de and Course Title:19EEE231- Electric circuit analysis Force in DC motor  PRINCIPLE OF OPERATION  When a current carrying conductor is placed in a magnetic field, the conductor experience a mechanical force.  Direction is given by Flemings left hand rule ( F- B; S-I; T- M)  Magnitude is F=B.I.L Consider a motor with one pair of poles, an armature with a single Explanation conductor coil and a commutator with only two segments, If is field current supplied to the field winding to establish the main field between the poles N and S. Ia is armature current via the carbon brushes. This current produces 54 magnetic fields around the armature conductors  FLEMING LEFT HAND RULE Magnitude is F=BIL F F 55 Magnetic field due to armature and field armature and field magnetic interaction 56  Application of DC Motors Crane Lathe machine Rolling mills Drillingmachine conveyors Grinders Elevators Blowers Rolling mills Compressors Punches Electric traction Shears Hoists and lifts December 3, 2024 Department of EECE, GIT Course Co 57 de and Course Title:19EEE131-BEEE  Lathe,blower,compressor,drilling machine December 3, 2024 Department of EECE, GIT Course Co 58 de and Course Title:19EEE131-BEEE TRANSFORMER December 3, 2024 Department of EECE, GIT Course Co 59 de and Course Title:19EEE231- Electric circuit analysis  TRANSFORMER A transformer basically is very simple static (or stationary) electro-magnetic passive electrical device that works on the principle of Faraday’s law of induction by converting electrical energy from one value to another. Transformers are capable of either increasing or decreasing the voltage and current levels of their supply, without modifying its frequency, or the amount of electrical power being transferred from one winding to another via the magnetic circuit. December 3, 2024 Department of EECE, GIT Course Co 60 de and Course Title:19EEE231- Electric circuit analysis  The main principle of operation of a transformer is mutual inductance between two circuits which is linked by a common magnetic flux. A basic transformer consists of two coils that are electrically separate and inductive, but are magnetically linked through a path of reluctance. December 3, 2024 Department of EECE, GIT Course Co 61 de and Course Title:19EEE231- Electric circuit analysis  A single phase voltage transformer basically consists of two electrical coils of wire, one called the “Primary Winding” and another called the “Secondary Winding”.  These two coils are not in electrical contact with each other but are instead wrapped together around a common closed magnetic iron circuit called the “core”.  The two coil windings are electrically isolated from each other but are magnetically linked through the common core allowing electrical power to be transferred from one coil to the other. December 3, 2024 Department of EECE, GIT Course Co 62 de and Course Title:19EEE231- Electric circuit analysis  TRANSFORMER OPERATION  Primary coil is supplied with a AC voltage.  Current drawn produces a magnetic field  Magnetic field transported to a secondary coil via a magnetic circuit  Magnetic field induces a voltage in secondary coil V V + + December 3, 2024 Department of EECE, GIT Course Co 63 de and Course Title:19EEE231- Electric circuit analysis  WORKING PRINCIPLE The working principle of transformer is very simple. It depends upon Faraday's law of electromagnetic induction. Actually, mutual induction between two or more winding is responsible for transformation action in an electrical transformer. According to these Faraday's laws, "Rate of change of flux linkage with respect to time is directly proportional to the induced EMF in a conductor or coil". December 3, 2024 Department of EECE, GIT Course Co 64 de and Course Title:19EEE231- Electric circuit analysis December 3, 2024 Department of EECE, GIT Course Co 65 de and Course Title:19EEE231- Electric circuit analysis  TRANSFORMER FEATURES It is a constant frequency device. It is a constant power device. It is a constant flux device. It is not an energy conversion device. Windings are electrically isolated and magnetically coupled. December 3, 2024 Department of EECE, GIT Course Co 66 de and Course Title:19EEE231- Electric circuit analysis  CONSTRUCTIONAL FEATURES Core Windings Transformer Tank Bushings December 3, 2024 Department of EECE, GIT Course Co 67 de and Course Title:19EEE231- Electric circuit analysis  TRANSFORMER CORE Generally, the name associated with the construction of a transformer is dependent upon how the primary and secondary windings are wound around the central laminated steel core. The two most common and basic designs of transformer construction are  Core type  Shell type December 3, 2024 Department of EECE, GIT Course Co 68 de and Course Title:19EEE231- Electric circuit analysis CORE- TYPE TRANSFORMER In core-type transformer, the windings are given to a considerable part of the core. The coils used for this transformer are form-wound and are of cylindrical type. Such a type of transformer can be applicable for small sized and large sized transformers. In the small sized type, the core will be rectangular in shape and the coils used are cylindrical. December 3, 2024 Department of EECE, GIT Course Co 69 de and Course Title:19EEE231- Electric circuit analysis  SHELL-TYPE TRANSFORMER In shell-type transformers the core surrounds a considerable portion of the windings. The comparison is shown in the figure below. December 3, 2024 Department of EECE, GIT Course Co 70 de and Course Title:19EEE231- Electric circuit analysis December 3, 2024 Department of EECE, GIT Course Co 71 de and Course Title:19EEE231- Electric circuit analysis  CORE Material--- Silicon steel (4.5 % of silicon) – Ferromagnetic material – Low reluctance, high permeability to the flow of magnetic flux lines – Low hysteresis loss – If silicon quantity is more, it tends to brittleness of steel. CRGO(cold rolled grain orientated) steel Laminations --- reduce eddy current loss December 3, 2024 Department of EECE, GIT Course Co 72 de and Course Title:19EEE231- Electric circuit analysis  Transformer Windings The two coils should have mutual inductance and a laminated steel core. The two coils are insulated from each other and from the steel core. The device will also need some suitable container for the assembled core and windings, a medium with which the core and its windings from its container can be insulated. December 3, 2024 Department of EECE, GIT Course Co 73 de and Course Title:19EEE231- Electric circuit analysis  The type of wire used as the main current carrying conductor in a transformer winding is either copper or aluminium. Small kVA power and voltage transformers used in low voltage electrical and electronic circuits tend to use copper conductors as these have a higher mechanical strength and smaller conductor size than equivalent aluminium types. December 3, 2024 Department of EECE, GIT Course Co 74 de and Course Title:19EEE231- Electric circuit analysis  Transformer Tank It gives mechanical protection to the windings It holds the insulating oil. December 3, 2024 Department of EECE, GIT Course Co 75 de and Course Title:19EEE231- Electric circuit analysis  a bushing is an insulated device that allows an electrical conductor to pass safely through an (usually) earthed conducting barrier such as the wall of a transformer December 3, 2024 Department of EECE, GIT Course Co 76 de and Course Title:19EEE231- Electric circuit analysis  Transformer oil  The insulating oil provides better insulation, protects insulation from moisture and transfers the heat produced in core and windings to the atmosphere.  Transformer oil is generally a mineral oil obtained by fractional distillation of crude oil. December 3, 2024 Department of EECE, GIT Course Co 77 de and Course Title:19EEE231- Electric circuit analysis  When a transformer is used to “increase” the voltage on its secondary winding with respect to the primary, it is called a Step-up transformer. When it is used to “decrease” the voltage on the secondary winding with respect to the primary it is called a Step-down transformer. As the transformer is basically a linear device, a ratio now exists between the number of turns of the primary coil divided by the number of turns of the secondary coil. This ratio, called the ratio of transformation, more commonly known as a transformers “turns ratio”, (TR). https://www.youtube.com/watch?v=Rp8qWms3Cjw December 3, 2024 Department of EECE, GIT Course Co 78 de and Course Title:19EEE231- Electric circuit analysis  Applications of Transformer used to increase or decrease the alternating voltages in electric power applications. used in voltmeter, ammeters, protective relay etc. used for step up low voltage in case of measurement. used for step down high voltage for safety. used in rectifier. used in voltage regulators, voltage stabilizers, power supplies etc. December 3, 2024 Department of EECE, GIT Course Co 79 de and Course Title:19EEE231- Electric circuit analysis THREE PHASE INDUCTION MOTOR December 3, 2024 Department of EECE, GIT Course Co 80 de and Course Title:19EEE231- Electric circuit analysis  Three Phase INDUCTION MOTOR The induction machine was invented by NIKOLA TESLA in 1888. The three-phase AC induction motor is a rotating electric machine that is designed to operate on a three-phase supply. Advantages It has simple and rugged construction. It is relatively cheap. It requires little maintenance. It has high efficiency and reasonably good power factor. It has self starting torque. Disadvantages It is essentially a constant speed motor and its speed cannot be changed easily. Its starting torque is inferior to d.c. shunt motor. December 3, 2024 Department of EECE, GIT Course Co 81 de and Course Title:19EEE131- BEEE  Constructional Features December 3, 2024 Department of EECE, GIT Course Co 82 de and Course Title:19EEE131- BEEE  Constructional Features An induction motor has two main parts – a stationary stator consisting of a steel frame that supports a hollow, cylindrical core core, constructed from stacked laminations having a number of evenly spaced slots, providing the space for the stator winding The rotor is separated from rotor by small air gap ranges from 0.4 mm to 4mm December 3, 2024 Department of EECE, GIT Course Co 83 de and Course Title:19EEE131- BEEE  STATOR The stator consists of wound poles that carry the supply current that induces a magnetic field in the conductor. The number of poles can vary between motor types but the poles are always in pairs(2,4,6…etc) The three coils form three windings distributed over several slots. These windings may be connected in star or delta and three terminations are brought out. December 3, 2024 Department of EECE, GIT Course Co 84 de and Course Title:19EEE131- BEEE December 3, 2024 Department of EECE, GIT Course Co 85 de and Course Title:19EEE131- BEEE December 3, 2024 Department of EECE, GIT Course Co 86 de and Course Title:19EEE131- BEEE December 3, 2024 Department of EECE, GIT Course Co 87 de and Course Title:19EEE131- BEEE December 3, 2024 Department of EECE, GIT Course Co 88 de and Course Title:19EEE131- BEEE December 3, 2024 Department of EECE, GIT Course Co 89 de and Course Title:19EEE131- BEEE December 3, 2024 Department of EECE, GIT Course Co 90 de and Course Title:19EEE131- BEEE  ROTOR – a revolving rotor composed of punched laminations, stacked to create a series of rotor slots, providing space for the rotor winding one of two types of rotor windings aluminum bus bars shorted together at the ends by two aluminum rings, forming a squirrel-cage shaped circuit (squirrel-cage) conventional 3-phase windings made of insulated wire (wound-rotor) » similar to the winding on the stator Two basic design types depending on the rotor design – squirrel-cage: conducting bars laid into slots and shorted at both ends by shorting rings. – wound-rotor: complete set of three-phase windings exactly as the stator. Usually Y-connected, the ends of the three rotor wires are connected to 3 slip rings on the rotor shaft. In this way, the rotor circuit is accessible. December 3, 2024 Department of EECE, GIT Course Co 91 de and Course Title:19EEE131- BEEE Squirrel Cage Rotor December 3, 2024 Department of EECE, GIT Course Co 92 de and Course Title:19EEE131- BEEE December 3, 2024 Department of EECE, GIT Course Co 93 de and Course Title:19EEE131- BEEE December 3, 2024 Department of EECE, GIT Course Co 94 de and Course Title:19EEE131- BEEE  Slip Ring Rotor December 3, 2024 Department of EECE, GIT Course Co 95 de and Course Title:19EEE131- BEEE December 3, 2024 Department of EECE, GIT Course Co 96 de and Course Title:19EEE131- BEEE December 3, 2024 Department of EECE, GIT Course Co 97 de and Course Title:19EEE131- BEEE December 3, 2024 Department of EECE, GIT Course Co 98 de and Course Title:19EEE131- BEEE December 3, 2024 Department of EECE, GIT Course Co 99 de and Course Title:19EEE131- BEEE Stator and Rotor Core Built from high-quality low-loss silicon steel laminations and flash-enamelled on both sides. Stator and Rotor Windings Have moisture proof tropical insulation embodying mica and high quality varnishes. Are carefully spaced for most effective air circulation and are rigidly braced to withstand centrifugal forces and any short-circuit stresses. The rotor fits inside the stator with a slight air gap between stator and rotor December 3, 2024 Department of EECE, GIT Course Co 100 de and Course Title:19EEE131- BEEE Enclosure Enclosure protects the electrical and operating parts of the motor from harmful effects of the environment in which the motor operates. Encloser consists of frame. Frame made of made of close-grained alloy cast iron. The stator is mounted inside the frame. December 3, 2024 Department of EECE, GIT Course Co 101 de and Course Title:19EEE131- BEEE Air-gap The stator rabbets and bore are machined carefully to ensure uniformity of air-gap. Shafts and Bearings Ball and roller bearings are used to suit heavy duty, toruble- free running and for enhanced service life. Fans Light aluminium fans are used for adequate circulation of cooling air and are securely keyed onto the rotor shaft. Slip-rings and Slip-ring Enclosures Slip-rings are made of high quality phosphor-bronze and are of moulded construction December 3, 2024 Department of EECE, GIT Course Co 102 de and Course Title:19EEE131- BEEE December 3, 2024 Department of EECE, GIT Course Co 103 de and Course Title:19EEE131- BEEE  Rotating Magnetic Field When we apply a three-phase supply to a three-phase distributed winding of a rotating machine, a rotating magnetic field is produced which rotates in synchronous speed. The magnetic flux produced by the current in each phase can be represented by the equations. This is a similar representation of current is a three-phase system as the flux is cophasial with the current. December 3, 2024 Department of EECE, GIT Course Co 104 de and Course Title:19EEE131- BEEE  Rotating Magnetic Field Where, φR, φY and φB are the instantaneous flux of corresponding Red, Yellow and Blue phase winding, φm amplitude of the flux wave. Hence the characteristics of rotating magnetic field are The resultant flux at any instant is equal to 1.5 times the maximum value of flux. The resultant flux rotates around the stator at synchronous speed. December 3, 2024 Department of EECE, GIT Course Co 105 de and Course Title:19EEE131- BEEE  Synchronous Speed The synchronous speed is the speed of the revolution of the magnetic field in the stator winding of the motor. It is the speed at which the electromotive force is produced by the alternating machine. The Synchronous Speed(Ns) is given by the relation shown below. P -- No of Poles f -- Frequency December 3, 2024 Department of EECE, GIT Course Co 106 de and Course Title:19EEE131- BEEE  INDUCTION MOTOR The induction machine was invented by NIKOLA TESLA in 1888. The three-phase AC induction motor is a rotating electric machine that is designed to operate on a three-phase supply. Advantages It has simple and rugged construction. It is relatively cheap. It requires little maintenance. It has high efficiency and reasonably good power factor. It has self starting torque. Disadvantages It is essentially a constant speed motor and its speed cannot be changed easily. Its starting torque is inferior to d.c. shunt motor. December 3, 2024 Department of EECE, GIT Course Co 107 de and Course Title:19EEE131- BEEE  Working Principle of Induction Motor  When the three-phase supply is given to the stator, the rotating magnetic field produced on it.  A rotating magnetic field with constant magnitude is produced, rotating with a speed Ns=120f/p rpm  Where f is the supply frequency and  P is the no. of poles and Ns is called the synchronous speed in rpm (revolutions per minute). December 3, 2024 Department of EECE, GIT Course Co 108 de and Course Title:19EEE131- BEEE  Working Principle of Induction Motor  The conductors of the rotor are stationary.  This stationary conductor cut the rotating magnetic field of the stator, and because of the electromagnetic induction, the EMF induces in the rotor.  This EMF is known as the rotor induced EMF, and it is because of the electromagnetic induction phenomenon.  The conductors of the rotor are short-circuited.  The relative motion between the rotating magnetic field and the rotor conductor induces the current in the rotor conductors.  As the current flows through the conductor, the flux induces on it. The direction of rotor flux is the same as that of the rotor current. December 3, 2024 Department of EECE, GIT Course Co 109 de and Course Title:19EEE131- BEEE  Working Principle of Induction Motor  Now we have two fluxes one because of the rotor and another because of the stator.  These fluxes interact with each other.  On one end of the conductor the fluxes cancel each other, and on the other end, the density of the flux is very high.  Thus, the high-density flux tries to push the conductor of the rotor towards the low- density flux region.  This phenomenon induces the torque on the conductor, and this torque is known as electromagnetic torque. December 3, 2024 Department of EECE, GIT Course Co 110 de and Course Title:19EEE131- BEEE  Working Principle of 3ɸ Induction Motor  The direction of electromagnetic torque and the rotating magnetic field is the same.  Thus, the rotor starts rotating in the same direction as that of the rotating magnetic field.  The speed of the rotor is always less than the rotating magnetic field or synchronous speed.  The rotor tries to run at the speed of the rotor, but it always slips away. Thus, the motor never runs at the speed of the rotating magnetic field, and this is the reason because of which the induction motor is also known as the asynchronous motor. December 3, 2024 Department of EECE, GIT Course Co 111 de and Course Title:19EEE131- BEEE  Applications of 3ɸ Induction motor The induction motor is mostly used in industrial applications. The squirrel cage induction motors are used in residential as well as industrial applications especially where the speed control of motors is not needed such as: Pumps and submersible Pressing machine Lathe machine Grinding machine Conveyor Flour mills Compressor And other low mechanical power applications December 3, 2024 Department of EECE, GIT Course Co 112 de and Course Title:19EEE231- Electric circuit analysis  Applications of 3ɸ Induction motor The slip ring motors are used in heavy load applications where the high initial torque is needed such as: Steel mills Lift Crane Machine Hoist Line shafts and other heavy mechanical workshops etc December 3, 2024 Department of EECE, GIT Course Co 113 de and Course Title:19EEE231- Electric circuit analysis SINGLE PHASE INDUCTION MOTOR December 3, 2024 Department of EECE, GIT Course Co 114 de and Course Title:19EEE231- Electric circuit analysis  SINGLE PHASE INDUCTION MOTOR Single phase power system is widely used as compared to three phase system for domestic purpose, commercial purpose and to some extent in industrial purpose. As the single phase system is more economical and the power requirement in most of the houses, shops, offices are small, which can be easily met by single phase system. December 3, 2024 Department of EECE, GIT Course Co 115 de and Course Title:19EEE231- Electric circuit analysis  Construction of Single Phase Induction Motor Stator: As its name indicates stator is a stationary part of induction motor. A single phase ac supply is given to the stator of single phase induction motor. The stator of the single phase induction motor has laminated stamping to reduce eddy current losses on its periphery. The slots are provided on its stamping to carry stator or main winding. stamping are made up of silicon steel. Department of EECE, GIT Course Code and Course December 3, 2024 Title:19EEE231- Electric circuit analysis 116  Rotor of Single Phase Induction Motor The construction of the rotor of the single phase induction motor is similar to the squirrel cage three phase induction motor. The rotor is cylindrical in shape and has slots all over its periphery. The slots are not made parallel to each other but are bit skewed as the skewing prevents magnetic locking of stator and rotor teeth and makes the working of induction motor more smooth and quieter i.e less noise. The squirrel cage rotor consists of aluminum, brass or copper bars. These aluminum or copper bars are called rotor conductors and are placed in the slots on the periphery of the rotor. The rotor conductors are permanently shorted by the copper or aluminum rings December 3, 2024 called Department the of EECE, GIT end rings. Course Code and Course 117 Title:19EEE231- Electric circuit analysis  Principle of operation A single phase induction motor is similar in construction to that of a polyphase induction motor with difference that its stator has only one winding. If such a stator is supplied with single phase alternating current, the field produced by it changes in magnitude and direction sinusoidally. Thus the magnetic field produced in the air gap is alternating one but not rotating as a result these kind of motors are NOT SELF STARTING. It is explained by double field revolving theory December 3, 2024 Department of EECE, GIT Course Co 118 de and Course Title:19EEE231- Electric circuit analysis  Double Field Revolving Theory December 3, 2024 Department of EECE, GIT Course Co 119 de and Course Title:19EEE231- Electric circuit analysis  Double Field Revolving Theory December 3, 2024 Department of EECE, GIT Course Co 120 de and Course Title:19EEE231- Electric circuit analysis  Consider two magnetic fields represented by quantities OA and OB of equal magnitude revolving in opposite directions as shown in above figure. The resultant of the two fields of equal magnitude rotating in opposite directions is alternating. Therefore an alternating current can be considered as having two components which are of equal in magnitude and rotating in opposite directions. From the above, it is clear that when a single phase alternating current is supplied to the stator of a single phase motor, the field produced will be of alternating in nature which can be divided into two components of equal magnitude December 3, 2024 one revolving in clockwise Department of EECE, GIT and other Course Coin counter clockwise 121 de and Course Title:19EEE231- Electric circuit analysis  If a stationary squirrel cage rotor is kept in such a field equal forces in opposite direction will act and the rotor will simply vibrate and there will be no rotation. But if the rotor is given a small jerk in any direction in this condition, it will go on revolving and will develop torque in that particular direction. It is clear from the above that a single phase induction motor when having only one winding is not a self-starting. Depending upon the methods for making asynchronous motor as Self Starting Motor, there are mainly four types of single phase induction motor namely,  Split phase induction motor,  Capacitor start inductor motor,  Capacitor start capacitor run induction motor,  Shaded pole induction motor. December 3, 2024 Department of EECE, GIT Course Co 122 de and Course Title:19EEE231- Electric circuit analysis  Split Phase Induction Motor In addition to the main winding or running winding, the stator of single phase induction motor carries another winding called auxiliary winding or starting winding. A centrifugal switch is connected in series with auxiliary winding. The purpose of this switch is to disconnect the auxiliary winding from the main circuit when the motor attains a speed up to 75 to 80% of the synchronous speed. December 3, 2024 Department of EECE, GIT Course Co 123 de and Course Title:19EEE231- Electric circuit analysis  Split Phase Induction Motor The running winding is inductive in nature. Our aim is to create the phase difference between the two winding and this is possible if the starting winding carries high resistance. Let us say Irun is the current flowing through the main or running winding, Istart is the current flowing in starting winding, and VT is the supply voltage. We know that for highly resistive winding the current is almost in phase with the voltage and for highly inductive winding the current lag behind the voltage by large angle. December 3, 2024 Department of EECE, GIT Course Co 124 de and Course Title:19EEE231- Electric circuit analysis  Split Phase Induction Motor The resultant of these two current is IT. The resultant of these two current produce rotating magnetic field which rotates in one direction.  Applications of Split Phase Induction Motor  Split phase induction motors have low starting current and moderate starting torque.  So these motors are used in fans, blowers, centrifugal pumps, washing machine, grinder, lathes, air conditioning fans, etc.  These motors are available in the size ranging from 1 / 20 to 1 / 2 KW. December 3, 2024 Department of EECE, GIT Course Co 125 de and Course Title:19EEE231- Electric circuit analysis  Capactor start single phase Induction motor In order to produce rotating magnetic field there must be some phase difference. In case of split phase induction motor we use resistance for creating phase difference but here we use capacitor for this purpose. We are familiar with this fact that the current flowing through the capacitor leads the voltage. So, in capacitor start inductor motor we are using two winding, the main winding and the starting winding. With starting winding we connect a capacitor so the current flowing in the capacitor i.e Ist leads the applied voltage by some angle, φst. December 3, 2024 Department of EECE, GIT Course Co 126 de and Course Title:19EEE231- Electric circuit analysis  Capactor start single phase Induction motor The running winding is inductive in nature so, the current flowing in running winding lags behind applied voltage by an angle, φm. Now there occur large phase angle differences between these two currents which produce a resultant current, I and this will produce a rotating magnetic field. Since the torque produced by these motors depends upon the phase angle difference, which is almost 90°.  Applications:  These motors have high starting torque hence they are used in conveyors, grinder, air conditioners, compressor, etc.  They are available up to 6 KW. December 3, 2024 Department of EECE, GIT Course Co 127 de and Course Title:19EEE231- Electric circuit analysis  Stepper motor Also known as stepping or step motors. This motor rotates through a fixed angular step in response to each input current pulse received by its controller. It works on the principle that unlike poles attract each other and like poles repel each other. When stator windings are connected with DC supply, it produces magnetic flux and established north and south poles. December 3, 2024 Department of EECE, GIT Course Co 128 de and Course Title:19EEE231- Electric circuit analysis  A stepper motor is made up of a rotor, which is normally a permanent magnet and it is, as the name suggests the rotating component of the motor. A stator is another part which is in the form of winding. The stator winding allows the current in the coil to change direction when the winding are grounded. The magnetic property of the stator changes and it will selectively attract and repel the rotor, thereby resulting in a stepping motion for the motor. December 3, 2024 Department of EECE, GIT Course Co 129 de and Course Title:19EEE231- Electric circuit analysis  Stator coils Rotor  Rotor Stator Outside Casing Coils Stator Rotor 1 N 2 2 S Internal components of a Stepper Motor 1 Cross Section of a Stepper Motor 1 Stators S N 2 2 S N 1 Rotor  Practical Stepper motor operation The top electromagnet (1) is turned The top electromagnet (1) is on, attracting the nearest teeth of turned off, and the right a gear-shaped iron rotor. With the electromagnet (2) is energized, teeth aligned to electromagnet 1, pulling the nearest teeth slightly they will be slightly offset from to the right. This results in a electromagnet 2 rotation of 3.6° in this example.  The left electromagnet (4) is The bottom electromagnet (3) enabled, rotating again by 3.6°. is energized; another 3.6° When the top electromagnet (1) is rotation occurs. again enabled, the teeth in the sprocket will have rotated by one tooth position; since there are 25 teeth, it will take 100 steps to make a full rotation in this example.  Applications of Stepper motor 3D printing equipment. Textile machines. Printing presses. Gaming machines. Medical imaging machinery. Small robotics. CNC milling machines. Welding equipment. December 3, 2024 Department of EECE, GIT Course Co 135 de and Course Title:19EEE231- Electric circuit analysis  Stepper motor applications Stepping Motor to move read-write head  Stepper motor applications Paper feeder on printers Stepper motors CNC lathes  SERVOMOTOR Also called control motors and have high torque capabilities. Used for precise speed and position control at high torques. A servomotor is a rotary actuator or linear actuator that allows for precise control of angular or linear position, velocity and acceleration. It consists of a suitable motor coupled to a sensor for position feedback. It also requires a relatively sophisticated controller, often a dedicated module designed specifically for use with servomotors. December 3, 2024 Department of EECE, GIT Course Co 138 de and Course Title:19EEE231- Electric circuit analysis The stator of ac servo motor consists of two separate windings uniformly distributed and separated at 90°, in space. Out of the two windings, one is referred as main or fixed winding while the other one is called control winding. A constant ac signal as input is provided to the main winding of the stator. However, as the name suggests, the control winding is provided with the variable control voltage. This variable control voltage is obtained from the servo amplifier. December 3, 2024 Department of EECE, GIT Course Co 139 de and Course Title:19EEE231- Electric circuit analysis December 3, 2024 Department of EECE, GIT Course Co 140 de and Course Title:19EEE231- Electric circuit analysis  Applications of servo motor used in robotics to activate movements, giving the arm to its precise angle. used to start, move and stop conveyor belts carrying the product along with many stages. For instance, product labeling, bottling and packaging used in robotic vehicle to control the robot wheels, producing plenty torque to move, start and stop the vehicle and control its speed. The servo motor is built into the camera to correct a lens of the camera to improve out of focus images. December 3, 2024 Department of EECE, GIT Course Co 141 de and Course Title:19EEE231- Electric circuit analysis  Applications of servo motor used in solar tracking system to correct the angle of the panel so that each solar panel stays to face the sun used in metal forming and cutting machines to provide specific motion control for milling machines used in Textiles to control spinning and weaving machines, knitting machines and looms used in automatic door openers to control the door in public places like supermarkets, hospitals and theatres December 3, 2024 Department of EECE, GIT Course Co 142 de and Course Title:19EEE231- Electric circuit analysis  BLDC MOTOR BLDC Motor also known as Brushless DC Motor. BLDC motor is operated without brushes to overcome certain difficulties. The basic difference between a brushed one and BLDC is operating with and without brushes. December 3, 2024 Department of EECE, GIT Course Co 143 de and Course Title:19EEE231- Electric circuit analysis  BLDC MOTOR A normal machine operates with brushes used to either collect or send current to the commutator. But due to the usage of brushes, sparking occurs at the brush location. As and when the rotor rotates it moves between brushes. At this time, the brushes undergo sparking during the rotation of the shaft. Due to this efficiency decrease and life expectancy are also reduced. To overcome these disadvantages, a BLDC is invented that performs a very smooth operation apart from the normal one. December 3, 2024 Department of EECE, GIT Course Co 144 de and Course Title:19EEE231- Electric circuit analysis  Construction of BLDC MOTOR BLDC motor also consists of two main parts a stator and a rotor. The rotor is the rotating part and the stator is the stationary part. The frame is used to hold the inner peripherals and also used to protect them from the environment. The rotor is fixed with some permanent magnets and stator has some coils that act as an electromagnet. The number of poles depends upon the operational requirement. December 3, 2024 Department of EECE, GIT Course Co 145 de and Course Title:19EEE231- Electric circuit analysis  Working Principle of BLDC MOTOR The BLDC operates on the same law as of a regular type. This type requires some coils to be energized in order to make the rotor rotate. The coils placed in the stator slots are named as A, B, and C. When the coil A is energized by a DC supply, it gets excited and attracts the rotor permanent magnet. Similarly, when the coil B is energized rotor permanent magnet is attracted this continues when the coil C is also energized. After the coil C is energized, the coil A is again energized but with negative polarity. This continues with the remaining coils as well with negative polarity. This cycle continues alternately, and the rotor continuously rotates. December 3, 2024 Department of EECE, GIT Course Co 146 de and Course Title:19EEE231- Electric circuit analysis December 3, 2024 Department of EECE, GIT Course Co 147 de and Course Title:19EEE231- Electric circuit analysis  Applications of BLDC motor small toys hairdryers electronic cars or bikes. projectors drills machines, power supply AC CCTV PC DVR Servers mixer grinders Trimmers air cleaners ventilation fan December 3, 2024 Department of EECE, GIT Course Co 148 de and Course Title:19EEE231- Electric circuit analysis