Inrush Current Limiting NTC Thermistors Designed to Withstand High Currents

Ametherm, Inc. today introduced a new series of inrush current limiting NTC thermistors designed to withstand high steady-state currents from 6 A to 50 A and 250 J to 800 J of input energy in a wide range of applications. Recognized by Underwriters Laboratories (UL) for ensured safety, AS Series devices provide lower current density, faster reset times, and a wider temperature range without derating compared with traditional inrush current limiters.

The thermistors released today limit inrush currents for the protection of pre-charge circuits in lithium-ion batteries; variable-frequency drives in sports equipment such as treadmills, high-speed computers, and processors; switch mode power supplies for plasma cutters and welders; and audio amplifiers, MRIs, and X-ray machines. Providing a simple one-component alternative to using power resistors with timers and relays, the AS Series reduces costs and greatly simplifies designs.

While traditional inrush current limiters handle approximately 167 A per square inch for the duration of the inrush current, AS Series devices are designed to withstand 400 A per square inch. This lower current density, in combination with a uniform temperature gradient throughout the disc, increases reliability by eliminating hot spots from fatigue.

The AS Series features Hot R from 0.0074 Ω to 0.380 Ω, resistance at 25 °C from .50 Ω to 50 Ω, and maximum capacitance at 680 VAC from 500 µF to 1730 µF. The devices are available with diameters of 30 mm and 36 mm.