
98 7 ◊ Transformers and Reactors
Transformers that rely on forced air from an external source or are
convection cooled may require some attention to airflow. If no air is
admitted to the enclosure, the internal air will become heated as it
rises through the coils and will tend to stratify with the hot air accu-
mulating at the top of the compartment. The only heat exchange is
then by radiation and convection from the enclosure, so the obvious
thing to do is to admit air at the bottom of the enclosure and exhaust it
at the top. But this may not end the matter. The coils represent a high
head loss to airflow, whereas the surrounding space offers little. ...