ring armature การใช้

• Sutton designed an electric continuous current dynamo with a practical ring armature.
• Early form of the Gramme ring armature with coils penetrating the interior of the ring.
• Brush's design modified the Gramme dynamo by shaping the ring armature like a disc rather than a cylinder shape.
• In 1860 an important improvement had been made by Dr . Antonio Pacinotti of Pisa who devised the first electric machine with a ring armature.
• This condition causes a serious defect in the action of ring armature armatures rendering the winding around the interior useless for the production of electromotive force.
• With more than a few coils on the Gramme ring armature, the resulting voltage waveform is practically constant, thus producing a near direct current supply.
• Figure 248 : Early form of Gramme ring armature, the core being shown cut through, and some of the coils displaced to make it clearer.
• While the Gramme ring permitted a more steady power output, it suffered from a technical design inefficiency due to how magnetic lines of force pass through a ring armature.
• For a very large power-generation armature several feet in diameter, using a hollow ring armature requires far less metal and is lighter than a solid core drum armature.
• Hence, in ring armatures only about half of the winding is effective, the rest being " " dead wire " ", adding its resistance to the circuit, thus decreasing the efficiency of the machine.
• A major turning point in the development of DC machines took place in 1864, when Antonio Pacinotti described for the first time the ring armature with its symmetrically grouped coils closed upon themselves and connected to the bars of a commutator, the brushes of which delivered practically non-fluctuating current.