x CONTENTS 



CHAPTER V 



ARMATURE WINDINGS AND SLOT INSULATION 

 ART. PAQB 



21. Introductory 83 



22. Ring- and drum-wound armatures 84 



23. Multiple and series windings 84 



24. Equalizing connections for multiple-wound armatures 90 



25. Insulation of armature windings 91 



26. Number of teeth on armature 93 



27. Number of commutator segments Potential difference between 



segments 93 



28. Nature and thickness of slot insulation 94 



29. Current density in armature conductors 96 



30. Length and resistance of armature winding 97 



CHAPTER VI 



LOSSES IN ARMATURES VENTILATION TEMPERATURE RISE 



31. Hysteresis and eddy-current losses in armature stampings ... 100 



32. Usual densities and losses in armature cores 104 



33. Ventilation of armatures 105 



34. Cooling surfaces and temperature rise of armature 107 



35. Summary, and syllabus of following chapters 113 



CHAPTER VII 

 FLUX DISTRIBUTION OVER ARMATURE SURFACE 



36. Air-gap flux distribution with toothed armatures 115 



37. Actual tooth density in terms of air-gap density 119 



38. Correction for taper of tooth '. . . 121 



39. Variation of permeance over pole pitch Permeance curve . . .123 



40. Open-circuit flux distribution and m.m.f. curves 128 



41. Practical method of predetermining flux distribution 129 



42. Open-circuit flux distribution curves as influenced by tooth satura- 



tion 132 



43. Effect of armature current in modifying flux distribution .... 135 



CHAPTER VIII 



COMMUTATION 



44. Introductory 140 



45. Theory of commutation 142 



46. Effect of slot flux .149 



47. Effect of end flux .151 



48. Calculation of end flux 155 



49. Calculation of slot flux cut by coil during commutation 160 



50. Corhmutating interpoles 165 



51. Example of interpole design 171 





