dc Generator Ppt
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1) DC generators convert mechanical energy to electrical energy through Faraday's law of electromagnetic induction. When a conductor moves through a magnetic field, an EMF is induced in the conductor. 2) The main components of a DC generator are the yoke, field electromagnets, armature, commutator, and brushes. The armature is wound with coils and rotates within the magnetic field produced by the field electromagnets to generate an EMF. 3) As the armature rotates, the commutator and brushes are used to periodically reverse the direction of current in the external circuit, thereby producing direct current. Losses in the generator arise from copper, iron, and mechanical components
dc Generator Ppt
- 1. Electric motors and generators Jitendra kumar 1103107
- 2. D.C. GENERATORS-CONSTRUCTION & OPERATION DC Generators Principle of operation Action of Commutator Constructional details of DC Machine Types of DC generators EMF Equation
- 3. DC Generator
- 4. DC motor
- 5. D.C. GENERATORS PRINCIPLE OF OPERATION DC generator converts mechanical energy into electrical energy. when a conductor move in a magnetic field in such a way conductors cuts across a magnetic flux of lines and e.m.f. produces in a generator and it is defined by faradays law of electromagnetic induction e.m.f. causes current to flow if the conductor circuit is closed.
- 6. Faradays laws First Law : Whenever the magnetic flux linked with a circuit changes, an e.m.f. is always induced in it. or Whenever a conductor cuts magnetic flux, an e.m.f. is induced in that conductor. Second Law : The magnitude of the induced e.m.f. is equal to the rate of change of flux linkages.
- 7. Faradays Law of Electromagnetic Induction A changing magnetic flux through a loop or loops of wire induces an electromotive force (voltage) in each loop.
- 8. Lenz’s Law “The induced currents in a conductor are in such a direction as to oppose the change in magnetic field that produces them..” “The direction of induced E.M.F in a coil (conductor) is such that it opposes the cause of producing it..”
- 9. Fleming's Right Hand Rule • The Thumb represents the direction of Motion of the conductor. • The First finger (four finger) represents Field. • The Second finger (Middle finger) represents Current
- 10. Fleming's Right Hand Rule
- 11. Are the basic requirements to be satisfied for generation of E.M.F 1.A uniform Magnetic field 2.A System of conductors 3.Relative motion between the magnetic field and conductors
- 13. Simple loop generator with slip ring
- 14. Generators Basic operation of the generator As the loop rotates, the magnetic flux through it changes with time This induces an e.m.f and a current in the external circuit The ends of the loop are connected to slip rings that rotate with the loop Connections to the external circuit are made by stationary brushes in contact with the slip rings
- 15. Simple loop generator with split ring
- 16. Working Principle of D.C Generator Schematic diagram of a simple DC Generator 1st half cycle(00 to 1800 ) Path of current ABR1B1MLR2B2CD 2st half cycle(1800 to 3600) Path of current DCR2B1MLB2R1BA
- 17. 1)Yoke - Acts as frame of the machine - Mechanical support - low reluctance for magnetic flux - High Permeability -- For Small machines -- Cast iron—low cost -- For Large Machines -- Cast Steel (Rolledsteel) Large DC machine Small DC machine
- 18. 2)pole cores and pole shoes
- 19. Constructional Details Of DC Machine Yoke: Rotor: Stator: Field electromagnets: Pole core and pole shoe: Brushes: Shaft: Armature: Coil: Commutator: Bearings:
- 20. Construction details of DC generator Cross section view of dc machine
- 22. 2)pole cores and pole shoes a) Pole core (Pole body) :- --Carry the field coils --Rectangle Cross sections -- Laminated to reduce heat losses --Fitted to yoke through bolts b) Pole shoe:- Acts as support to field poles and spreads out flux Pole core & Pole shoe are laminated of annealed steel (Of thickness of 1mm to 0.25 mm)
- 23. 4)commutator :--Hard drawn copper bars segments insulated from each other by mica segments (insulation) -- Between armature & External circuit -- Split-Rings (acts like Rectifier AC to DC )
- 24. 5&6 Bearings and Brushes 5)Brushes and brush gear:- Carbon, Carbon graphite, copper used to Collects current from commutation (in case of Generator) 6)Shaft and bearings:- Shaft-- Mechanical link between prime over and armature Bearings– For free rotation
- 26. Armature Winding Armature Winding is classified into two types: Lap winding Wave windings
- 28. Lap Winding: are used in machines designed for low voltage and high current armatures are constructed with large wire because of high current Eg: - are used is in the starter motor of almost all automobiles The windings of a lap wound armature are connected in parallel. This permits the current capacity of each winding to be added and provides a higher operating current. No of parallel path, A=P ; P = no. of poles
- 30. Wave winding: are used in machines designed for high voltage and low current their windings connected in series When the windings are connected in series, the voltage of each winding adds, but the current capacity remains the same are used is in the small generator. No of parallel path, A=2,
- 32. Commutation process in D.C Generator Commutation is the positioning of the DC generator brushes so that the commutator segments change brushes at the same time the armature current changes direction.
- 33. The total losses in a dc machine 1.Cu losses 2.Iron losses 3.Mechanical losses Cupper losses are mainly due to the current passing through the winding. 1.Armature cu losses (30 to 40% of full load losses) Cu losses 2.Shunt field cu losses(20 to30% of full load losses) 3.Series field cu losses
- 34. 1.Cu losses Armature cu losse s= Ia 2 Ra Ra=Armature resistance , Ia= Armature current --Losses due to brush contact resistance is usually include in armature cu losses Shunt field cu losses = Ish 2Rsh Rsh=Shunt field resistance, Ish=Shunt field current Series field cu losses = Ise 2Rse Rse=Series field resistance , Ise=Series field current
- 35. 2.Iron losses (Magnetic losses) (20 to 30% of full load losses) 1)Hysteresis losses 2)Eddy current losses
- 36. 1)Hysteresis losses (Wh) The losses is due to the reversal of magnetisation of the armature core Every portion of the rating core passes under N and S poles alternately. There by attaining S and N polarity respectively. The core undergoes one complete cycle of magnetic reversal after passing under one pair of poles. P=No. of poles N= Armature speed in rpm frequency of magnetic reversals f=NP 120 The losses depends upon the volume and B max and frequency of reversals. Hysteresis losses is given by steinmetz formula Wh=η B1.6 maxf V wats V=Volume of the core in m3 η= Steinmetz hysteresis coefficient
- 37. 2)Eddy current losses:-(We) when the armature core rotates, it cuts the magenetic flux hence an e.m.f induced in in the body of the core according to faradays law of electro magnetic induction. This e. m.f through small sets up large current in the body of the core due to its mall resistance. This current is known as “Eddy Current” We=k B2 maxf2t2v2 watts Bmax=maximum flux densities f=Freequency of the magenetic reversals v=volume of the armaturecore t=Thick ness of lamination
- 38. Efficiency of D.C Generator Efficiency of generator is defined as the ratio of output power to input power Efficiency (η) =output 100 input input=output+ losses (or) output=input-losses For D.C generator input mechanical & output electrical
- 40. We hope our idea would benefit a lot… Thank you!