Circuits for providing overcurrent protection are disclosed herein. The circuits feature depletion mode MOSFETs connected to resistive elements, preferably, Positive Temperature Coefficient (PTC) devices, configured in such a way so that the voltage across the PTC device is the same as the gate-to-source voltage of the MOSFET. The circuit may further be configured using a TVS diode, for clamping the drain-to-source voltage of the MOSFET during the overcurrent events. Heat transfer between the MOSFET and the PTC device facilitates overcurrent protection. A two-terminal device including a depletion mode MOSFET, a PTC device, and a TVS diode may provide overcurrent protection to other circuits. A bidirectional circuit c including two MOSFETS disposed on either side of a PTC is also contemplated for AC voltage overcurrent protection.

A thermal hazard protection circuit for a transportation vehicle comprises an interruptible power circuit connected between a power source and load, and a failsafe circuit operative to permanently interrupt current flow under an overcurrent condition. The interruptible power circuit comprises a Positive Temperature Coefficient (PTC) component in series with bi-stable relay configured as a SPST switch. The failsafe circuit comprises a failsafe relay energized by current in the interruptible power circuit. An input of the failsafe relay is connected to the power source, and a normally closed (NC) output (not connected to the input so long as the failsafe relay is energized) is connected to a control input of the bi-stable relay that opens the SPST switch. In an overcurrent condition, the PTC component limits current flow, switching the failsafe relay input to its NC outputs, providing a control signal to open the SPST switch, rendering the interruptible power circuit non-conductive and isolating the load.

Circuits for providing overcurrent protection are disclosed herein. The circuits feature depletion mode MOSFETs connected to resistive elements, preferably, Positive Temperature Coefficient (PTC) devices, configured in such a way so that the voltage across the PTC device is the same as the gate-to-source voltage of the MOSFET. The circuit may further be configured using a TVS diode, for clamping the drain-to-source voltage of the MOSFET during the overcurrent events. Heat transfer between the MOSFET and the PTC device facilitates overcurrent protection. A two-terminal device including a depletion mode MOSFET, a PTC device, and a TVS diode may provide overcurrent protection to other circuits. A bidirectional circuit c including two MOSFETS disposed on either side of a PTC is also contemplated for AC voltage overcurrent protection.

A current cut-off device for high-voltage DC current includes: between a primary point and an intermediate point, a primary diversion member and, in parallel, a primary surge protector; a secondary mechanical switch between the intermediate point and the secondary point; a main resonator whose terminal is linked to the secondary point; a main oscillation switch; a main surge protector, in parallel with a main capacitance of the main resonator; wherein the main oscillation switch includes three terminals linked respectively to the primary point, to the intermediate point and to the other terminal of the main resonator; the changeover switch can switch at least between three direct, inverting and isolated states.

An electric component with a fail safe element is disclosed. In an embodiment a component includes a functional element and a fail safe element electrically interconnected therewith, wherein the fail safe element is configured to ensure a minimum resistance or a minimum conductivity of the component in the event of a failure of the functional element.

A surface-mounted polymer PTC overcurrent protection element having a small package size, comprising a PTC chip, an insulating layer (30), end electrodes (41, 42), and at least one conductive member (60). A dividing gap is designed on a first conductive electrode (21) to form first and second conductive areas (211, 212); the conductive member (60) is arranged at the edge or at least a corner of the first conductive area (211) side of the PTC chip, is used for conducting the first conductive area (211) and a second conductive electrode (22) on the PTC chip, and is not in contact with the end electrodes (41, 42); the main portion comprised in the dividing gap (70) of the first conductive electrode (21) is parallel to the longitudinal direction of the first end electrode (41) and the second end electrode (42). Also provided is a preparation method for the protection element. Thus, the miniaturized overcurrent protection element can satisfy the current PCB process to achieve requirements of mass production. It is convenient to design an overcurrent protection element resistance scheme, and reduce adjustment of a PTC core material formulation.

A motor is connectable to a single-phase AC power supply and forms a hermetic compressor. The motor includes a main circuit connected in parallel with the auxiliary circuit, and a winding structure having a main winding arranged as part of the main circuit and an auxiliary winding arranged as part of the auxiliary circuit. The motor includes a rotor arranged to be rotated by a current in the winding structure. To provide a motor durable and cheap to manufacture and to ensure a suitable response to overload situations, the auxiliary circuit has a first section and a second section extending in parallel where an NTC is inserted in the first section. A PTC is inserted in the second section, and a relay is arranged to activate and deactivate current in the first section of the auxiliary circuit based on a current level in the main circuit.

A pPTC heating device having areas with different power densities distributed over the surface of the device. The device is constructed using a base layer composed of a pPTC material having a layer of sectioned conductive plates disposed over and under the layer of pPTC such as to control the path of the current through the device, thereby controlling resistance of the device and the power density of the device.

The present invention provides an apparatus having a protecting element for protecting the apparatus in an emergency, wherein the protecting element is a polymer PTC element, the polymer PTC element has a polymer PTC member, and the polymer PTC member is formed from a polymer composition containing a polyvinylidene fluoride as a main component.

A protection circuit including an inrush current detector operable to detect an inrush current from a DC link is disclosed herein. The inrush current detector includes a transistor switch that is turned on in normal operation of the protection circuit. The protection circuit operates to detect when the voltage across the transistor switch exceeds a threshold voltage in response to a detected inrush current, and in response operates to turn off the transistor switch.