The ambient temperature rise is also called the Celsius
rise. It's the amount of temperature rise the motor can withstand during
normal operation. This value is listed in degrees Celsius (°C). A typical
open motor can withstand a rise of 40°C (104°F) and an enclosed motor
can withstand a 50°C (122°F) rise. This means the motor should not be
exposed to environments where the temperature is 104°F above the ambient.
If the ambient is considered 72°F, it means the motor is limited to temperatures
of 176°F. Another classification that will help determine the amount
of temperature a motor will be able to withstand is the type of insulation
the motor winding has. The classes of insulation that are used with motors and the amount of temperature these classes can handle are listed here.