ECE5320 Mechatronics Assignment#01: Literature Survey on Sensors and Actuators Topic: AC induction motorOutlineReference listTo explore further (survival pointers of web references etc)Major ApplicationsOverviewOverview - GeneralOverview – SlipPrinciple – General OperationPrinciple – SlipRotor TypesSquirrel Cage RotorSlip Ring RotorSolid Core RotorPrinciple – Single Phase StartingPrinciple – Starting Larger MotorsTypical ApplicationMajor SpecificationsLimitationsCost and availabilityNonlinearitiesSlide 22Slide 23Other ConsiderationsSlide 25ECE5320 MechatronicsAssignment#01: Literature Survey on Sensors and Actuators Assignment#01: Literature Survey on Sensors and Actuators Topic: AC induction motorPrepared by: Mike TygerDept. of Electrical and Computer Engineering Utah State University3/06/200901/13/19ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuatorsSlide-2Outline –Reference List–Explore Further–Major applications–Overview–Basic working principles–Typical Application–Major specifications–Limitations01/13/19ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuatorsSlide-3Reference list•Wikipedia, ‘Induction motor ’, en.wikipedia.org/wiki/AC_induction_motor.•Wikipedia, ‘Squirrel-cage rotor’, en.wikipedia.org/wiki/Squirrel-cage_rotor. •Wikipedia, ‘Slip Ring’, en.wikipedia.org/wiki/Slip_ring.01/13/19ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuatorsSlide-4To explore further (survival pointers of web references etc) •http://www.physclips.unsw.edu.au/jw/electricmotors.html#ACmotors –Animations of how an AC motor operates•http://hyperphysics.phy-astr.gsu.edu/HBASE/magnetic/indmot.html–Physics of an AC motorMajor Applications•Drive motor for small household appliances–Fans–Blenders–Vacuums•Drive motor for larger applications–Pumps–Compressors–Treadmills–Forced air heating system01/13/19ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuatorsSlide-5Overview•A polyphase sinusoidal voltage passed though the stators of a motor produces a rotating magnetic field.•By placing conductive material in the rotor the rotating magnetic field will induce a current in the rotor which will in turn create a magnetic field in the rotor.•The rotor magnetic field is opposed by the stator magnetic filed so a torque is generated. 01/13/19ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuatorsSlide-6Overview - General01/13/19ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuatorsSlide-7A 3-Phase power supply creates a rotating magnetic field in an induction motor.Illustration courtesy of wikipedia.orghttp://upload.wikimedia.org/wikipedia/commons/thumb/a/a6/Rotatingfield.png/180px-Rotatingfield.pngOverview – Slip01/13/19ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuatorsSlide-8For a current to be induced the magnetic field in relation to the rotor must be changing so the speed of the rotor will never be the same as the rotational speed of the magnetic field. This difference is known as slip.F = supply frequencyP = Number of Stator PolesNs = speed of the rotating fieldS = slipPrinciple – General Operation 01/13/19ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuatorsSlide-9An AC induction motor does not have any direct supply onto the rotor. A secondary current is induced in the rotor. To achieve this, stator windings are arranged around the rotor so that when energized with a polyphase supply they create a rotating magnetic field pattern which sweeps past the rotor. This changing magnetic field pattern induces a current in the rotor conductors. These currents create a magnetic field which interacts with the rotating magnetic field created by the stator and the rotor will turn.Principle – Slip 01/13/19ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuatorsSlide-10For a current to be induced in the rotor, the speed of the rotor and the speed of the rotating magnetic field in the stator must be different. If the rotor reaches the speed of the rotating magnetic field the current will stop being induced and the rotor will slow slightly until a current is re-induced and then the rotor continues as before. The difference between the speed of the rotor and speed of the rotating magnetic field in the stator is called slip. It is the ratio between the relative speed of the magnetic field as seen by the rotor (the slip speed) to the speed of the rotating stator field.Rotor Types•Squirrel Cage Rotor–Most common type of rotor•Slip Ring Rotor–Least common type of rotor•Solid Core Rotor–Simplest rotor to manufacture01/13/19ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuatorsSlide-11Squirrel Cage Rotor01/13/19ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuatorsSlide-12The core of the rotor is built of a stack of iron laminations. The image above shows only three laminations of the stack but many more are used. Longitudinal conductive bars of aluminum or copper are set into grooves in the laminations and connected together at both ends by shorting rings forming a cage-like shape.http://upload.wikimedia.org/wikipedia/commons/thumb/d/da/Squirrel_cage.jpg/180px-Squirrel_cage.jpgSlip Ring Rotor01/13/19ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuatorsSlide-13A slip ring rotor replaces the bars of the squirrel cage rotor with windings that are connected to slip rings. A slip ring is a conductive band mounted to and insulated from the motor shaft. If the slip rings are shorted to each other the rotor behaves similarly to the squirrel cage rotor.Solid Core Rotor01/13/19ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuatorsSlide-14A solid core rotor uses a solid piece of mild steel for the rotor. The rotation is caused by the induced currentPrinciple – Single Phase Starting01/13/19ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuatorsSlide-15In a single phase induction motor a starting circuit must be used to start rotation of the rotor. A single phase induction motor can rotate in either direction. The starting circuit determines the rotational direction.For small motors it is usual to "shade" the stator poles by means of a single turn of heavy copper wire around one corner of the pole. The current induced in the single turn is out of phase with the supply current and so causes an out-of-phase component in the magnetic field. This imparts sufficient torque to
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