The windings of the standard motors are insulated with materials of class F (overtemperature of 105°C) even if they are designed for limit overtemperatures of class B (thermal supply). The copper wire is insulated with a double layer of insulating enamel of class H (overtemperature of 125°C).  This means longer life of the insulating devices and the possibility to use, for brief periods, the motors over the load and temperature limits normally established for such motors. An increased insulation is supplied, on request, for the particular use of motors with inverters.