Modular converter

The present invention relates to a converter for an electric motor or a transformer and more particularly but not exclusively a converter for a motor that is asynchronous or synchronous, that has permanent magnets, or that operates on DC. A converter for an electric motor or transformer, the converter being comprising a connection box having passages for electrical conductors and having a semiconductor electronic module removably fixed to the connection box. The electronic module has a radiator-forming box that is open at one end, at least one electronic card at least partially embedded in a resin cast inside said radiator-forming box, and at least one connector emerging from the resin. The opening of the radiator-forming box enables it to be fitted to the connection box. The connection box has at least one window giving access to the connector(s) of the electronic module.