3.1.17 When is a forced cooling fan installed on a gear motor with a frequency inverter?

Since a normal electric motor is cooled on its own by a mechanical fan, the self-cooling cannot be reduced as desired. The guideline value for this is 30Hz; if the frequency inverter control falls below this frequency, a forced cooling fan must be used. This guide value applies to drives in operating mode S9, i.e., operation with non-periodic load and speed changes.