In the case where an aluminium pan (pot) approaches the cooker coil, it works the same as if the secondary winding of the transformer is short-circuited. The primary winding leads higher current that can destroy the transformer. For that reason the cooker has the protective function that detects the excessive current and switches off the coil source, together with the failure warnings. (It works the same way as if there is no pot on the plate—there is no consumption on the ‘secondary’ side.)