Abstract: Electronic device for thermal protection of a load (M) by cutting off the polyphase power supply to said load, including current transformers (Ti.sub.1, Ti.sub.2, Ti.sub.3) installed on the wires (L.sub.1, L.sub.2, L.sub.3) of the polyphase line supplying power to said load and connected to an electronic processor circuit (3) adapted to generate a command, characterized in that the outputs of the current transformers (Ti.sub.1, Ti.sub.2, Ti.sub.3) are connected to detector means (51, 52, 53) which supply to the processor circuit (3) logic signals the levels of which depend on the direction or the magnitude of the output current of each current transformer.

Abstract: This invention concerns an electronic thermal protection device adapted to interrupt the power supply on a multiphase line comprising a temperature detector including a resistive element thermally coupled to a temperature sensor that is connected to a digital processing circuit adapted to outputt a control order as a function of the overload detected by the temperature sensor. The temperature detector resistive element is connected to various rectifiers, each powered by a current transformer installed on one line wire such that the sum of the currents delivered by the rectifiers flows in the resistive element.

Abstract: An electronic protection device for providing thermal protection of a load by cutting off the multiphase supply of power to the load includes a thermal sensor having at least one resistive element thermally coupled to a temperature sensor connected to an electronic processor circuit. This circuit generates a command instruction in response to any overload detected by the temperature sensor. Each resistive element of the thermal sensor is fed with current by a current sensor on a phase wire supplying power to the load.