CHAPTER IV 



ARMATURE CORE VENTILATING PIECES 



WHILE amongst the work of the earliest dynamo builders we find 

 frequent instances of careful attention to the provision of means 

 for ventilation, it may nevertheless be said that this aspect of 

 dynamo design has been greatly neglected. In the present 

 treatise we are concerned only with the ventilation of the armature, 

 and, in this particular chapter, with the means for providing radial 



FIG. 75. Ventilating Distance-piece. Allmanna Svenska 

 Elektriska Aktiebolaget. 



ducts through the armature core. At the time when slot-wound 

 armatures first came into extensive use, the most progressive 

 manufacturers adopted the plan of providing a number of these 

 core ducts, and practice in these companies quickly settled down 

 into following the rule that there should be one duct for every 

 four or five inches of core length. These ducts were often only 

 6 or 7 mm. wide, and were generally so obstructed by the distance- 

 pieces as to be very inefficient. Some dozen years of experience 

 has made a slight impression on all but the most obdurately 



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