Abstract :
THE ADVENT of the diesel-electric locomotive and its rapid large-scale acceptance by the railroads of the United States has brought to the fore many problems for which solutions must be found. Among the problems related to this tremendous increase in heavy d-c electric traction equipment is that of adequate joints between coil leads and commutator bars in motors subjected to severe operating conditions. This is a problem of long standing in motors operated at high temperatures, but it has become much more acute with the development and use of insulating materials that will withstand more and more heat. The first substantial increase in permissible operating temperatures of such equipment was brought about a number of years ago by the introduction of full Class-B insulation to replace the then standard Class-A, or composite, insulation. This permissible temperature now has been further increased by the acceptance of Class-H (Silicone) insulation as standard in certain types of traction motors.
