TDK Electronics launches S series current limiters for high power systems

Applications such as switch-mode power supplies, frequency converters, photovoltaic inverters, uninterruptible power supplies, and soft-start motors increasingly require robust protection against inrush currents. These systems operate with high capacitances and rapidly rising input loads, making stable, reliable inrush current suppression essential for long-term efficiency and component longevity.

Expanded High-Power Capability with the S Series
To address these needs, TDK Corporation has released its new S series of inrush current limiters, comprising the S30 and S36 NTC thermistor families. The devices are engineered for demanding power environments, offering maximum steady-state currents up to 35 A and energy absorption capabilities up to 750 J. This positions the series among the higher-performance NTC ICL options available for designers needing both durability and wide operating margins.

Design Characteristics that Reduce Losses
The S30 series, built with a 30 mm disk and 7.5 mm lead spacing, supports power handling up to 19 W, while the larger 36 mm S36 variant extends this capability to 25 W through its 19 mm lead spacing. Both versions are rated for the 55/170/21 climatic category under IEC 60068-1, enabling stable operation across broad temperature extremes. The components cover resistance values from 2 Ω to 20 Ω, permissible capacitances up to 13,050 µF at 240 V AC, and continuous current ratings from 10 A to 35 A.

A key differentiator from conventional resistor-and-relay soft-start solutions is the reduced power loss during continuous operation. By maintaining low resistance once self-heated, the NTC-based design improves system efficiency, which can translate directly to lower energy consumption for end users. Competing fixed-resistor approaches tend to generate higher losses and require additional switching circuitry, making the S series a simpler, more energy-efficient alternative.

Robust Construction for Demanding Environments
Both the S30 and S36 series use leaded, coated NTC thermistor construction with tinned copper wire. The coating material is flame-retardant to UL 94 V-0, and the devices are designed for stable electrical characteristics over their service life. This design focus helps ensure predictable behavior under repeated inrush conditions, a critical requirement for industrial and renewable-energy systems exposed to frequent power cycling.

Support Tools for Component Selection
To assist designers in selecting the correct thermistor for their power profile, TDK provides a web-based NTC ICL selection tool. By entering system parameters, users can quickly evaluate the most suitable device for achieving the desired balance of protection, energy efficiency, and thermal performance.

www.tdk-electronics.tdk.com