An arrangement to cool a coil, comprising an enclosure, which at least partially incorporates or houses the coil, and a device to create an airflow to cool the coil, wherein the coil comprises at least one cooling channel to guide the airflow through the windings of the coil and an outer air duct lying radially in the outer circumference area of the coil or lying radially inside below an outer part of the coil, characterized in that an air guidance plate is placed at or near one longitudinal end of the outer air duct and/or of the coil to prevent bypasses of the airflow and/or to block at least partially the airflow through and/or along the outer air duct, achieves the object to cool a coil, especially a coil of a transformer, in an efficient manner using space-saving means.