Self-Protecting PTC Thermistors EPCOS / TDK Self-Protecting PTC Thermistors are suitable for smoothing capacitors in power supplies in the event of a short circuit. These self-protecting PTC thermistors are ideal for high pulse currents and a high number of operating cycles. Inrush current limiters are not damaged when directly connected to Vmax, even without additional current limitation. Applications for EPCOS / TDK Self-Protecting PTC Thermistors include inrush current limiters (charging resistors) for smoothing and DC link capacitors and for the replacement of high-power fixed resistors for capacitor charging.