EN 206 - Power Electronics and Machines

1 EN 206 - Power Electronics and MachinesInduction MotorSuryanarayana DoollaDepartment of Energy Science and EngineeringIndian Institute of Technology, March 2011 Prof. Doolla ()EN 2061/1607 March 20111 / 16 Lecture Organization - ModulesIntroduction and Power Semiconductor SwitchesModule 1: TransformersModule 2: AC/DC converter / RectifierModule 3: DC Machines and DrivesModule 4: DC/DC converterModule 5: induction MachineModule 6: DC/AC converter / InverterModule 7: AC/AC converter / Cyclo converterModule 8: Synchronous MachineModule 9: Special Topics: Machines , HVDC, APFProf.

2 Doolla ()EN 2062/1607 March 20112 / 16basic principleRotating Magnetic FieldWhen balanced polyphase currents flow in a balanced polyphasewindings, a rotating magnetic field is a 3 phase machine , the three windings are displaced from eachother by 120oelectrical space degrees along the air-gap of rotating magnetic field can be verified both bygraphical and mathematical Doolla ()EN 2063/1607 March 20113 / 16basic principleRotating Magnetic FieldWhen balanced polyphase currents flow in a balanced polyphasewindings, a rotating magnetic field is a 3 phase machine , the three windings are displaced from eachother by 120oelectrical space degrees along the air-gap of rotating magnetic field can be verified both bygraphical and mathematical Doolla ()

3 EN 2063/1607 March 20113 / 16basic principleRotating Magnetic FieldWhen balanced polyphase currents flow in a balanced polyphasewindings, a rotating magnetic field is a 3 phase machine , the three windings are displaced from eachother by 120oelectrical space degrees along the air-gap of rotating magnetic field can be verified both bygraphical and mathematical Doolla ()EN 2063/1607 March 20113 / 16basic principleRotating Magnetic FieldThree phase winding space distributed by 120oelectrical, Three coilsrepresent three phase winding and Three phase instantaneous currentsProf.

4 Doolla ()EN 2064/1607 March 20114 / 16basic principleRotating Magnetic FieldState-1Ia=Im;Ib= Im/2;Ic= Im/2 The maximum mmf set by thecurrent isFm,The resultant mmfFris given byFr=Fm+2 Fmcos(60)2directedalong a axisState-2Ia= Im/2;Ib= Im/2;Ic=ImThe resultant mmfFris given byFr=Fm+2 Fmcos(60)2directedalong c axisProf. Doolla ()EN 2065/1607 March 20115 / 16basic principleRotating Magnetic FieldState-3Ia= Im/2;Ib=Im;Ic= Im/2 The resultant mmfFris given byFr=Fm+2 Fmcos(60)2directedalong b axisWhen a poly phase current flow in a balanced poly phase circuit, arotating magnetic field of constant magnitude is created and thespeed of rotation is synchronous speedThe effect of polyphase currents in polyphase windings is equivalentto the mechanical rotation of permanent magnets, or dc excited fieldpoles, at synchronous Doolla ()EN 2066/1607 March 20116 / 16basic principleRotating Magnetic FieldState-3Ia= Im/2;Ib=Im.

5 Ic= Im/2 The resultant mmfFris given byFr=Fm+2 Fmcos(60)2directedalong b axisWhen a poly phase current flow in a balanced poly phase circuit, arotating magnetic field of constant magnitude is created and thespeed of rotation is synchronous speedThe effect of polyphase currents in polyphase windings is equivalentto the mechanical rotation of permanent magnets, or dc excited fieldpoles, at synchronous Doolla ()EN 2066/1607 March 20116 / 16basic principleProduction of RMF- Space Phasor MMFProf. Doolla ()EN 2067/1607 March 20117 / 16basic principleRotating flux in a polyphase machineWhen a poly phase current flow in a balanced poly phase circuit, arotating magnetic field of constant magnitude is created and thespeed of rotation is synchronous speedSynchronous speed(Ns) is given byNs=120fP, whereNsin mmf is assumed to be sinusoidally distributed in space ie.

6 ,along the air gap peripheryThe stator mmf and rotor mmf produce set of pole pairs which eithertend to attract or repel each otherThis attraction or repulsion results in development of electromagnetictorqueElectromagnetic torque is proportional to product of interactingmagnetic fields and sine of electrical space angle between theirmagnetic Doolla ()EN 2068/1607 March 20118 / 16basic principleRotating flux in a polyphase machineWhen a poly phase current flow in a balanced poly phase circuit, arotating magnetic field of constant magnitude is created and thespeed of rotation is synchronous speedSynchronous speed(Ns) is given byNs=120fP, whereNsin mmf is assumed to be sinusoidally distributed in space ie.

7 ,along the air gap peripheryThe stator mmf and rotor mmf produce set of pole pairs which eithertend to attract or repel each otherThis attraction or repulsion results in development of electromagnetictorqueElectromagnetic torque is proportional to product of interactingmagnetic fields and sine of electrical space angle between theirmagnetic Doolla ()EN 2068/1607 March 20118 / 16basic principleRotating flux in a polyphase machineWhen a poly phase current flow in a balanced poly phase circuit, arotating magnetic field of constant magnitude is created and thespeed of rotation is synchronous speedSynchronous speed(Ns) is given byNs=120fP, whereNsin mmf is assumed to be sinusoidally distributed in space ie.

8 ,along the air gap peripheryThe stator mmf and rotor mmf produce set of pole pairs which eithertend to attract or repel each otherThis attraction or repulsion results in development of electromagnetictorqueElectromagnetic torque is proportional to product of interactingmagnetic fields and sine of electrical space angle between theirmagnetic Doolla ()EN 2068/1607 March 20118 / 16basic principleRotating flux in a polyphase machineWhen a poly phase current flow in a balanced poly phase circuit, arotating magnetic field of constant magnitude is created and thespeed of rotation is synchronous speedSynchronous speed(Ns) is given byNs=120fP, whereNsin mmf is assumed to be sinusoidally distributed in space ie.

9 ,along the air gap peripheryThe stator mmf and rotor mmf produce set of pole pairs which eithertend to attract or repel each otherThis attraction or repulsion results in development of electromagnetictorqueElectromagnetic torque is proportional to product of interactingmagnetic fields and sine of electrical space angle between theirmagnetic Doolla ()EN 2068/1607 March 20118 / 16basic principleRotating flux in a polyphase machineWhen a poly phase current flow in a balanced poly phase circuit, arotating magnetic field of constant magnitude is created and thespeed of rotation is synchronous speedSynchronous speed(Ns) is given byNs=120fP, whereNsin mmf is assumed to be sinusoidally distributed in space ie.

10 ,along the air gap peripheryThe stator mmf and rotor mmf produce set of pole pairs which eithertend to attract or repel each otherThis attraction or repulsion results in development of electromagnetictorqueElectromagnetic torque is proportional to product of interactingmagnetic fields and sine of electrical space angle between theirmagnetic Doolla ()EN 2068/1607 March 20118 / 16basic principleRotating flux in a polyphase machineWhen a poly phase current flow in a balanced poly phase circuit, arotating magnetic field of constant magnitude is created and thespeed of rotation is synchronous speedSynchronous speed(Ns) is given byNs=120fP, whereNsin mmf is assumed to be sinusoidally distributed in space ie.