Smithsonian Report. 1947. — Bass 



Plate 2 



1. Silicone-insulated test motors are operated alternately at temperatures up to 

 310 degrees centigrade and exposed to 100 percent relative humidity. Tests 

 show that moisture is excluded after thousands of hours of thermal aging. 



Left, rl:t>^ i; iiiMilalcd niotdr (lulvA alti'i .j,7(i() liour.-- at 200 deiirci'.-- centigi-aiie; 

 right, silicone-insulated motor failed after 5,178 hours at 300 degrees centigrade. 

 Both windings look about alike and show at)Out the same degree of deteriora- 

 tion. The class B motor caught fire on failure, while the silicone-insulated motor 

 failed because of oxidation of the copper. . 



