Abstract: 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.

Abstract: A magnet is affixed to a shaft or other pivoting or rotating member of a switch mechanism, on the axis of rotation. The radial position of the resulting magnetic field is monitored. A change in the magnetic field radial position, optionally in excess of a threshold, indicates the onset of switch actuation, prior to operative actuation of the switch mechanism. The radial position of the magnetic field is sensed by a magnetic rotary encoder. The detection of switch actuation onset may be used to remove current from a circuit prior to operative switch actuation. Because the magnet is rigidly affixed to the shaft, there is no lost motion. Because the shaft position and encoder are magnetically coupled, the detection mechanism contains no moving parts and no mechanical linkage or coupling, and its performance does not degrade due to shock, thermal effects, vibration, or wear.

Abstract: A magnet is affixed to a shaft or other pivoting or rotating member of a switch mechanism, on the axis of rotation. The radial position of the resulting magnetic field is monitored. A change in the magnetic field radial position, optionally in excess of a threshold, indicates the onset of switch actuation, prior to operative actuation of the switch mechanism. The radial position of the magnetic field is sensed by a magnetic rotary encoder. The detection of switch actuation onset may be used to remove current from a circuit prior to operative switch actuation. Because the magnet is rigidly affixed to the shaft, there is no lost motion. Because the shaft position and encoder are magnetically coupled, the detection mechanism contains no moving parts and no mechanical linkage or coupling, and its performance does not degrade due to shock, thermal effects, vibration, or wear.

Abstract: An overcurrent protection circuit for low-voltage, high-current electrical systems comprises a Positive Temperature Coefficient (PTC) resistor in series with an auto-reset thermal breaker. The breaker allows for intermittent current within an assumed product usage duty cycle, and repeatedly trips and resets on sustained high current usage or during a short-circuit fault. The PTC resistor limits current in the system to a low value when the temperature rises to the PTC resistor's trip point. The PTC resistor protects the system from thermal damage during the non-breaker-tripped portions of sustained high current use, or during continuous low-current use. The use of both the PTC resistor and auto-reset breaker provides thermal overcurrent protection while allowing for performance claims based on an assumed duty cycle of product use.

Abstract: An overcurrent protection circuit for low-voltage, high-current electrical systems comprises a Positive Temperature Coefficient (PTC) resistor in series with an auto-reset thermal breaker. The breaker allows for intermittent current within an assumed product usage duty cycle, and repeatedly trips and resets on sustained high current usage or during a short-circuit fault. The PTC resistor limits current in the system to a low value when the temperature rises to the PTC resistor's trip point. The PTC resistor protects the system from thermal damage during the non-breaker-tripped portions of sustained high current use, or during continuous low-current use. The use of both the PTC resistor and auto-reset breaker provides thermal overcurrent protection while allowing for performance claims based on an assumed duty cycle of product use.