When is the PTC thermistor as suitable for ICL?

The thermistors are classified into a positive temperature coefficient thermistor (PTC) and a negative temperature coefficient thermistor (NTC) according to the temperature coefficient. In some applications, the use of PTC thermistors as ICLs provides superior performance. The resistance of NTCICL when the power is turned on depends on the ambient temperature. At lower ambient temperatures, the resistance of the NTC thermistor will be higher, resulting in lower charging current and longer charging time.

On the other hand, higher ambient temperatures control the ability of NTCICL to suppress inrush currents because NTC thermistors are already in a low-impedance state. This temperature dependence can cause problems for some applications, especially for applications with a wide operating temperature range. For example, an outdoor power source used in the winter in the north may never be able to rise enough to keep the resistance value low enough.

Conversely, the hot water circulation pump may be already hot at startup, which prevents the NTC thermistor from controlling the inrush current. After the system is turned off, the ice cold time of the NTC thermistor usually varies from 30S to 120S, depending on the specific equipment, installation method and ambient temperature. The charging current can be controlled again only after the NTCICL is completely cold. In many cases, the ice cold time is fast enough; however, sometimes the surge current needs to be controlled before the NTC is sufficiently cold and cold.