Abstract: The invention is directed at an electric power converter, such as an electric motor drive for driving an electric motor. The converter includes a cooling system with a heat sink for dissipating thermal energy generated by the converter and with coolant flow means for cooling the heat sink, first measuring means for measuring the coolant inlet temperature, second measuring means for measuring the heat sink temperature, estimating means for estimating the thermal energy transferred to the heat sink, wherein the converter is provided for estimating the thermal resistance of the heat sink based on the measured temperatures and the estimated thermal energy transferred to the heat sink, for comparing the estimated thermal resistance to reference values and for outputting a signal, if the difference between the estimated thermal resistance and the reference values exceeds a threshold value. The invention is also directed at a method for operating the electric power converter.

Abstract: A method for cooling a device such as an electric motor drive or a general power converter, said device comprising a heatsink, electronic components connected to the heatsink, a heat pipe connected to the heatsink, an inlet air temperature measuring device and a cooling fan. According to the method, the drive establishes whether the inlet air temperature is below a first temperature threshold value and operates the cooling fan at a low inlet air temperature speed regime if the inlet air temperature is below the first temperature threshold value. The invention is also directed at a device such as an electric motor drive or a general power converter for performing the cooling method.