Page 194 - Electrician - TT (Volume 1)

ELECTRICIAN - CITS

Slip rings
Copper / Brass /phosphorous bronze slip rings
Yoke

small dc generator - cast iron – cheap
big dc generator of cast steel / rolled steel – high permeability
Pole core& pole shoe
small dc generator - solid pole core and laminated pole shoe

big dc generator – both are laminated
Armature core
Cylindrical – laminations of approx. 0.5mm, with keyway and airducts.
Types of dc generators
Permanent magnet dc generators

Applications
Dynamos
Meggar
Advantages

Simple to build and requires very less maintenance
Disadvantages
As the field strength is fixed, voltage variation is not possible by flux control
Difficult to regulate.
Separately excited dc generators
Electromagnet is used as field. Separate source of power needed to excite. Excitation is independent of load.
Wide voltage variations are attainable.

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CITS : Power - Electrician & Wireman - Lesson 30-37