{"id":2699,"date":"2024-08-24T20:55:50","date_gmt":"2024-08-24T20:55:50","guid":{"rendered":"https:\/\/workhouse.sweetdishy.com\/?p=2699"},"modified":"2024-08-24T20:55:50","modified_gmt":"2024-08-24T20:55:50","slug":"self-excited-dc-generators","status":"publish","type":"post","link":"https:\/\/workhouse.sweetdishy.com\/index.php\/2024\/08\/24\/self-excited-dc-generators\/","title":{"rendered":"SELF-EXCITED DC GENERATORS"},"content":{"rendered":"\n

A DC generator whose field winding is excited by the current supplied by the generator itself is called a self-excited DC generator. In a self-excited DC generator, the field coils may be connected in parallel with the armature, in series with the armature or partly in series, and partly in parallel with the armature winding. Accordingly, the self-excited generators may be classified as follows:<\/p>\n\n\n\n

    \n
  1. Shunt-wound generators:<\/strong>\u00a0In this generator, the field winding is connected across the armature winding forming a parallel or shunt circuit. Therefore, full terminal voltage is applied across the field winding. A very small current\u00a0I<\/em>sh<\/sub>\u00a0flows through it, because this winding has many turns of fine wire having very high resistance\u00a0R<\/em>sh<\/sub>\u00a0(of the order of 100 \u03a9). Its conventional diagram is shown in\u00a0Figure 11.17.\u00a0\"image\"Fig. 11.17<\/strong>\u00a0\u00a0Conventional diagram of a shunt wound DC generatorImportant relations<\/em>Shunt field current,\u00a0I<\/em>sh<\/sub>\u00a0=\u00a0V<\/em>\/R<\/em>sh<\/sub>where\u00a0R<\/em>sh<\/sub>\u00a0is the shunt field winding resistance. The field current\u00a0I<\/em>sh<\/sub>\u00a0is practically constant at all loads, and therefore, the DC shunt machine is considered to be constant flux machine.Armature current,\u00a0I<\/em>a<\/sub>\u00a0=\u00a0I<\/em>L<\/sub>\u00a0+\u00a0I<\/em>sh<\/sub>; terminal voltage,\u00a0V<\/em>\u00a0=\u00a0E<\/em>g<\/sub>\u00a0\u2212\u00a0I<\/em>a<\/sub>R<\/em>a<\/sub>Including brush contact drop,\u00a0V<\/em>\u00a0=\u00a0E<\/em>g<\/sub>\u00a0\u2212\u00a0I<\/em>a<\/sub>\u00a0R<\/em>a<\/sub>\u00a0\u2212 2\u03c5<\/em>b<\/sub>Power developed =\u00a0E<\/em>g<\/sub>\u00a0I<\/em>a<\/sub>; power output =\u00a0VI<\/em>L<\/sub><\/li>\n\n\n\n
  2. Series-wound generators:<\/strong>\u00a0In this generator, the field winding is connected in series with the armature winding forming a series circuit. Therefore, full line current\u00a0I<\/em>L<\/sub>\u00a0or armature current\u00a0I<\/em>a<\/sub>\u00a0flows through it. Since the series field winding carries full-load current, it has a few turns of thick wire having low resistance (usually of the order of less than 1 \u03a9). Its conventional diagram is shown in\u00a0Figure 11.18.\u00a0\"image\"Fig. 11.18<\/strong>\u00a0\u00a0Conventional diagram of a series wound DC generatorImportant relations<\/em>Series field current,\u00a0I<\/em>se<\/sub>\u00a0=\u00a0I<\/em>L<\/sub>\u00a0=\u00a0I<\/em>a<\/sub>Series field winding resistance =\u00a0R<\/em>se<\/sub>Terminal voltage,\u00a0V<\/em>\u00a0=\u00a0E<\/em>g<\/sub>\u00a0\u2212\u00a0I<\/em>a<\/sub>\u00a0R<\/em>a<\/sub>\u00a0\u2212\u00a0I<\/em>se<\/sub>\u00a0R<\/em>se<\/sub>\u00a0=\u00a0E<\/em>g<\/sub>\u00a0\u2212\u00a0I<\/em>a<\/sub>\u00a0(R<\/em>a<\/sub>\u00a0+\u00a0R<\/em>se<\/sub>)Including brush contact drop,\u00a0V<\/em>\u00a0=\u00a0E<\/em>g<\/sub>\u00a0\u2212\u00a0I<\/em>a<\/sub>\u00a0(R<\/em>a<\/sub>\u00a0+\u00a0R<\/em>se<\/sub>) \u2212 2v<\/em>b<\/sub>Power developed =\u00a0E<\/em>g<\/sub>I<\/em>a<\/sub>; power output =\u00a0VI<\/em>L<\/sub>\u00a0=\u00a0VI<\/em>a<\/sub>Note:<\/strong>\u00a0The flux developed by the series field winding is directly proportional to the current flowing through it (i.e., \u0278<\/em>\u00a0\u221d\u00a0I<\/em>se<\/sub>). However, it is only true before magnetic saturation. After saturation, flux becomes constant even if the current flowing through it is increased.<\/li>\n\n\n\n
  3. Compound-wound generators:<\/strong>\u00a0In a compound-wound generator, there are two sets of field windings on each pole. One of them is connected in series (having few turns of thick wire) and the other is connected in parallel (having many turns of fine wire) with armature. A compound-wound generator may be classified as follows:\n
      \n
    1. Long shunt:<\/strong>\u00a0In this generator, the shunt field winding is connected in parallel with the combination of both armature and series field winding. The conventional diagram of lone shunt compound generator is shown in\u00a0Figure 11.19.\u00a0\"image\"Fig. 11.19<\/strong>\u00a0\u00a0Conventional diagram of a long shunt compound wound DC generatorImportant relations<\/em>Shunt field current,\u00a0\"image\"Series field current,\u00a0I<\/em>se<\/sub>\u00a0=\u00a0I<\/em>a<\/sub>\u00a0=\u00a0I<\/em>L<\/sub>\u00a0+\u00a0I<\/em>sh<\/sub>Terminal voltage,\u00a0V<\/em>\u00a0=\u00a0E<\/em>g<\/sub>\u00a0\u2212\u00a0I<\/em>a<\/sub>\u00a0R<\/em>a<\/sub>\u00a0\u2212\u00a0I<\/em>se<\/sub>\u00a0R<\/em>se<\/sub>\u00a0=\u00a0E<\/em>g<\/sub>\u00a0\u2212\u00a0I<\/em>a<\/sub>\u00a0(R<\/em>a<\/sub>\u00a0+\u00a0R<\/em>se<\/sub>)\u00a0Including brush contact drop,\u00a0V<\/em>\u00a0=\u00a0E<\/em>g<\/sub>\u00a0\u2212\u00a0I<\/em>a<\/sub>\u00a0(R<\/em>a<\/sub>\u00a0+\u00a0R<\/em>se<\/sub>) \u2212 2v<\/em>b<\/sub>Power developed =\u00a0E<\/em>g<\/sub>\u00a0I<\/em>a<\/sub>; power output =\u00a0VI<\/em>L<\/sub><\/li>\n\n\n\n
    2. Short shunt:<\/strong>\u00a0In this generator, the shunt field winding is connected in parallel with only armature winding. The conventional diagram of short-shunt compound generator is shown in\u00a0Figure 11.20.\u00a0\"image\"Fig. 11.20<\/strong>\u00a0\u00a0Conventional diagram of a short shunt compound wound DC generatorImportant relations<\/em>Series field current,\u00a0I<\/em>se<\/sub>\u00a0=\u00a0I<\/em>L<\/sub>Shunt field current,\u00a0\"image\"I<\/em>a<\/sub>\u00a0=\u00a0I<\/em>L<\/sub>\u00a0+\u00a0I<\/em>sh<\/sub>Terminal voltage,\u00a0V<\/em>\u00a0=\u00a0E<\/em>g<\/sub>\u00a0\u2212\u00a0I<\/em>a<\/sub>R<\/em>a<\/sub>\u00a0\u2212\u00a0I<\/em>L<\/sub>\u00a0R<\/em>se<\/sub>Including brush contact drop,\u00a0V<\/em>\u00a0=\u00a0E<\/em>g<\/sub>\u00a0\u2212\u00a0I<\/em>a<\/sub>\u00a0R<\/em>a<\/sub>\u00a0\u2212\u00a0IL R<\/em>se<\/sub>\u00a0\u2212 2v<\/em>b<\/sub>Power developed =\u00a0E<\/em>g<\/sub>\u00a0I<\/em>a<\/sub>; power output =\u00a0VI<\/em>L<\/sub><\/li>\n<\/ol>\n<\/li>\n<\/ol>\n","protected":false},"excerpt":{"rendered":"

      A DC generator whose field winding is excited by the current supplied by the generator itself is called a self-excited DC generator. In a self-excited DC generator, the field coils may be connected in parallel with the armature, in series with the armature or partly in series, and partly in parallel with the armature winding. […]<\/p>\n","protected":false},"author":1,"featured_media":2700,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[414],"tags":[],"class_list":["post-2699","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-dc-machines-generators-and-motors"],"jetpack_featured_media_url":"https:\/\/workhouse.sweetdishy.com\/wp-content\/uploads\/2024\/08\/direct-current-generator-components-fig1.webp","_links":{"self":[{"href":"https:\/\/workhouse.sweetdishy.com\/index.php\/wp-json\/wp\/v2\/posts\/2699","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/workhouse.sweetdishy.com\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/workhouse.sweetdishy.com\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/workhouse.sweetdishy.com\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/workhouse.sweetdishy.com\/index.php\/wp-json\/wp\/v2\/comments?post=2699"}],"version-history":[{"count":1,"href":"https:\/\/workhouse.sweetdishy.com\/index.php\/wp-json\/wp\/v2\/posts\/2699\/revisions"}],"predecessor-version":[{"id":2701,"href":"https:\/\/workhouse.sweetdishy.com\/index.php\/wp-json\/wp\/v2\/posts\/2699\/revisions\/2701"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/workhouse.sweetdishy.com\/index.php\/wp-json\/wp\/v2\/media\/2700"}],"wp:attachment":[{"href":"https:\/\/workhouse.sweetdishy.com\/index.php\/wp-json\/wp\/v2\/media?parent=2699"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/workhouse.sweetdishy.com\/index.php\/wp-json\/wp\/v2\/categories?post=2699"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/workhouse.sweetdishy.com\/index.php\/wp-json\/wp\/v2\/tags?post=2699"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}