322 Shipboard Electrical Power Systems
For example, a motor with a design temperature rise of 80°C in 40°C ambient air, the
design average operating temperature of the coils would be 40 + 80 = 120°C, so the
insulation must be rated for 130°C (Class B) to allow a 10°C margin for local hotspot.
If the motor is operating in the boiler room with 65°C ambient air, then its tem-
perature rise must be limited to 55°C, so that the operating temperature does not rise
above the 120°C design limit. For this, the motor horsepower must be appropriately
selected and derated for higher ambient temperature.
Safety in arc welding and metal cutting: For manual arc welding, metal cutting,
or other processes requiring hands-on operations, the industry ...