Inrush current limiting for solid state devices using NTC resistor

This paper proposes a passive method to limit inrush currents for solid state switching devices, such as circuit breakers, contactors, relays, and other electrical apparatuses. The method proposes to limit inrush currents with a negative temperature coefficient resistor in series connection with the power semiconductor switching device and integrated into the switching device. This new configuration permits to avoid excessive overrating of power semiconductor devices and thus to reduce the cost of solid state switching devices. In the event of an inrush current at closing of the device, the negative temperature coefficient resistor limits the current to an acceptable level. In this way, overheating and failure of power semiconductor switching devices can be avoided.