Static frequency converter, especially a frequency converter controlling and/or adjusting the performance data of an electromotor

A pump assembly comprising an electromotor, a rotor chamber for receiving fluid to be circulated, an additional chamber which also receives said fluid to be circulated and communicates with said rotor chamber, a housing which surrounds said electromotor and defines said additional chamber, a heat conductive casing arranged in said additional chamber, a frequency converter comprising an input circuit and an output circuit arranged inside said casing, said input circuit being coupled to a power source and said output circuit being electrically coupled to said electromotor, and heat conductive and electrically insulative filler means which fill the remaining space inside said casing, said casing being in thermal contact with and sealed from said fluid in said additional chamber, whereby said filler means conducts heat from said input and output circuits to said casing, and said casing thereafter dissipates said heat to said fluid to be circulated.