COMPARATIVE PERFORMANCE OF OPEN AND TOTALLY ENCLOSED MACHINES

Continuous improvements in insulating materials, manufacturing consist encies in sealed windings, and extensive laboratory testing of various systems show that synchronous machines with NEMA II construction can replace totally enclosed machines, Tests on windings in corrosive atmo sphere show that sealed insulation systems are impervious to the envir onment. Standard maintenance ensures that incendive arcing will not be generated in potentially hazardous environments. When compared to tot ally enclosed machines, the NEMA II-type construction is lighter, more efficient, has lower short-circuit current and associated torques, an d is easier to maintain.