FARTS OF A DYNAMO-ELECTRIC MACHINE 



91 



trough -and pushed into the slot and the formed coil is 

 pushed and hammered down into the slot inside this paper 

 trough. This insulating trough extends beyond the ends 

 of the armature core so that as the formed coil is hammered 

 into place there may be no risk of sharp edges on the iron 

 core cutting through the insulation of the coil and so 

 grounding it on the armature core. 



Shape of Conductor. In small machines the armature 

 conductor is generally a round wire, which can easily be 



FIG. 51. Insulation in Slot of a Bar-wound Armature. Allis-Chalmers 



Co. 



bent and shaped in sizes up to about No. 4. B. & S If 

 it is necessary to use larger cross-section than No. 4, several 

 smaller wires may be used in parallel. When the cross- 

 section necessary is larger than that of a No. 4 wire, 

 a specially shaped conductor would probably be used. A 

 round wire does not use the space in a slot very economi- 

 cally and so a rectangular shaped conductor is generally 

 used on large machines. Fig. 51 shows a cross-section 

 through the slot of a high voltage machine showing how 

 such copper bars fit into a slo,t, with the insulation around 



