API St 547 pdf download.General-purpose Form-wound Squirrel Cage Induction Motors—250 Horsepower and Larger 1.3 UNUSUAL SERVICE CONDITIONS Unusual service conditions should be brought to the atten- tion of those responsible for the design, manufacture, applica- tion, and operation of the motor. Among such unusual conditions are: a. Exposure to: 1. Combustible, explosive, abrasive, or conductive dust. 2. Dirty operating conditions...