The disclosure relates to electrical converters for use in aircraft electrical power systems and to methods of operating such electrical converters to maintain reliable operation of semiconductor components over varying cosmic radiation levels at altitude. Exemplary embodiments include an electrical converter comprising: a converter circuit having a plurality of semiconductor devices configured to convert an input electrical supply to an output electrical supply; and a controller connected configured to receive an input altitude signal, wherein the controller is further configured to control a temperature of the plurality of semiconductor devices according to the received input altitude signal to reduce an effect of increased incident cosmic radiation on the converter circuit.