logging in or signing up 505456 aSGuest12825 Download Post to : URL : Related Presentations : Let's Connect Share Add to Flag Embed Email Send to Blogs and Networks Add to Channel Copy embed code: Embed: Flash iPad Dynamic Copy Does not support media & animations Automatically changes to Flash or non-Flash embed WordPress Embed Customize Embed URL: Copy Thumbnail: Copy The presentation is successfully added In Your Favorites. Views: 683 Category: Science & Tech.. License: All Rights Reserved Like it (0) Dislike it (0) Added: February 11, 2009 This Presentation is Public Favorites: 1 Presentation Description No description available. Comments Posting comment... Premium member Presentation Transcript Welcome toLectures on D.C.Machine : 2/11/2009 Welcome toLectures on D.C.Machine Slide 2: 2/11/2009 D. C. Generator Slide 3: 2/11/2009 Portable D. C. Generator DIRECT CURRENT MACHINES : 2/11/2009 DIRECT CURRENT MACHINES DC machine Construction The major advantages of DC machines are: easy speed and torque regulation. The stator of the DC motor has poles, which are excited by DC current to produce magnetic fields. The rotor has a ring-shaped laminated iron-core with slots. Coils with several turns are placed in the slots. The distance between the two legs of the coil is about 180 electric degrees. N S Stator with with poles Brush Rotor Field Slide 5: 2/11/2009 D. C. Generator Principle of Operation When a conductor rotates in a magnetic field, dynamically induced e.m.f is produced in it according to Faraday’s law of electromagnetic induction Slide 6: 2/11/2009 Generated EMF Let Slide 7: 2/11/2009 Hence, according to Faraday’s Laws of electromagnetic induction, Slide 8: 2/11/2009 For Wave wound Generator No. of Parallel Paths = 2 No. of Conductors (in series) in 1 path = Z/2 Slide 9: 2/11/2009 For Lap wound Generator No. of Parallel Paths = P No. of Conductors (in series) in 1 path = Z/P Slide 10: 2/11/2009 In General, Generated EMF Slide 11: 2/11/2009 Also, For a given D.C. Machine, Z, P and A are constants Hence, Putting Slide 12: 2/11/2009 Types of D.C. Generators According to the way in which their fields are excited, generators are classified into : Separately excited D.C. Generator Self- excited D.C. Generator Slide 13: 2/11/2009 Separately excited D.C. Generators are those whose field magnets are energized from an independent source of D.C. Current Ra = Armature Resistance Slide 14: 2/11/2009 ii) Self excited D.C. Generators are those whose field magnets are energized by the currents produced by the generators themselves. There are 3 types of self-excited D.C. Generators named according to the manner in which their field coils are connected to the armature. These are : Shunt wound D.C. Generator Series wound D.C. Generator Compound wound D.C. Generator Slide 15: 2/11/2009 Shunt wound D.C. Generator Rsh – Shunt Field Resistance Ra - Armature Resistance Slide 16: 2/11/2009 ii) Series wound D.C. Generator Slide 17: 2/11/2009 iii) Compound wound D.C. Generator Short Shunt Slide 18: 2/11/2009 Long Shunt Slide 19: 2/11/2009 Ex.1 A D.C. Shunt Generator delivers 450A at 230V and the resistance of the shunt field and armature are 50O and 0.03 O respectively. Calculate the generated EMF. Slide 20: 2/11/2009 Ex.2 An 8 - pole D.C. Shunt Generator with 778 wave wound armature conductors running at 500 rpm supplies a load of 12.5O resistance at terminal voltage of 250V. The armature resistance is 0.24O and the field resistance is 250O . Find the armature current, the generated EMF and the flux per pole. You do not have the permission to view this presentation. In order to view it, please contact the author of the presentation.