OVERVOLTAGE PROTECTION DEVICE SUBMODULES INCLUDING UNBREAKABLE THERMAL DISCONNECT MECHANISMS AND METHODS INCLUDING THEM

Abstract

A surge protection device (SPD) module includes a module housing, first and second module electrical terminals mounted on the module housing, a surge limiting element electrically connected between the first and second module electrical terminals, and a thermal disconnect mechanism. The thermal disconnect mechanism is mounted in a ready configuration, where the surge limiting element is electrically connected to the second module electrical terminal. The thermal disconnect mechanism can be repositioned to electrically disconnect the surge limiting element from the second module electrical terminal.The thermal decoupling mechanism includes: an electrode electrically connected to the surge limiting element; a decoupling spring resiliently deflectable and electrically connected to the electrode in the ready configuration; a tin that secures the decoupling spring in electrical connection to the electrode in the ready configuration; and a heat sink member thermally superposed between the electrode and the tin, the heat sink member having thermal capacity. The tin can melt in response to overheating of the surge limiting element. The decoupling spring is configured to electrically disconnect the surge limiting element from the second electrical terminal of the module when the tin melts.The thermal capacitance of the reservoir member regulates and dissipates heat from the surge limiting element to prevent tin melting in response to at least some surge currents through the SPD module.