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8/20/2019 Edwin Beee Unit 2
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UNIT II
Electrical Mechanics
1
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CONTENTS
Construction of DC machine
Working principle of DC generator
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DC Machine Construction
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DC machine stator with poles visible.
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Rotor of a dc machine
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Cutaway view of a dc machine
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Working principle of DC generator
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Con'ersion of (C to DC
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Construction of DCgenerator
• ( DC generator has the follo*ingparts
• 1+ ,oke
• 2+ -el. s/stem
• $+ (rmature
•
+Commutator• %+ 0rushes
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,oke
• ,oke of DC generator ser'es t*o purposes
• 3i+ It hol.s the magnetic pole cores of thegenerator an. acts as co'er of the
generator4 3ii+ It carries the magnetic -el.5u4
• In small generator /oke are ma.e of castiron4 Cast iron is cheaper in cost
• lighter cast steel or rolle. steel isprefera7le for constructing /oke of largesi8e DC generator4
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9iel. s/stem
• The pole core is -e. to the inner peripher/ ofthe /oke 7/ means of 7olts through the /oke an.into the pole 7o./4
• The pole shoes are so t/picall/ shape. thatthe/ sprea. out the magnetic 5u in the air gapan. re.uce the reluctance of the magnetic path4
• The -el. coils or pole coils are *oun. aroun. thepole core4 These are a simple coil of insulate.copper *ire or strip *hich place. on the pole*hich place. 7et*een /oke an. pole shoes
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• The purpose of armature core is tohol. the armature *in.ing
• (rmature *in.ing are generall/forme. *oun.4 The con.uctors areplace. in the armature slots *hichare line. *ith tough insulating
material4
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Commutator
• It collects current from armature an.sen.s it to the loa. as .irect current4It actuall/ takes alternating current
from armature an. con'erts it to.irect current an. then sen. it toeternal loa.4
EE 6!1 Electrical machines "Iunit # DC motors
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http://www.electrical4u.com/electric-current-and-theory-of-electricity/http://www.electrical4u.com/electric-current-and-theory-of-electricity/http://www.electrical4u.com/electric-current-and-theory-of-electricity/http://www.electrical4u.com/electric-current-and-theory-of-electricity/http://www.electrical4u.com/electric-current-and-theory-of-electricity/http://www.electrical4u.com/electric-current-and-theory-of-electricity/
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0rushes
• The 7rushes are ma.e of car7on4 These are rectangular 7lock shape.4 The onl/ function of these car7on
7rushes of DC generator is to collectcurrent from commutator segments4
The 7rushes are house. in the
rectangular 7o shape. 7rush hol.er
EE 6!1 Electrical machines "Iunit # DC motors
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http://www.electrical4u.com/principle-of-dc-generator/http://www.electrical4u.com/electric-current-and-theory-of-electricity/http://www.electrical4u.com/electric-current-and-theory-of-electricity/http://www.electrical4u.com/principle-of-dc-generator/