What do motor insulation classes represent?

Motor insulation classes define the maximum operating temperature the insulation can withstand continuously. Class A allows 105C, Class B 130C, Class F 155C, and Class H 180C. Higher class insulation costs more but allows operation at higher ambient temperatures or with higher loading. Motor life halves for every 10C above rated temperature. Modern industrial motors typically use Class F insulation with Class B temperature rise, providing a safety margin.