TDK introduces compact thermofuse varistors for surge protection

CIRCUIT PROTECTION TDK introduces compact thermofuse varistors for surge protection

2026-03-19 From TDK 1 min Reading Time

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TDK Corporation has introduced the MT40 series of ThermoFuse varistors (ordering code B72240M), a new generation of surge protection components (SPC) that combine a compact design with advanced safety features.

TDK has introduced compact thermofuse varistors designed to provide high surge protection of up to 50 kA in industrial and power applications.(Source: TDK) — TDK has introduced compact thermofuse varistors designed to provide high surge protection of up to 50 kA in industrial and power applications.
(Source: TDK)

Thanks to their patented overmolding technology and integrated thermal disconnecting system, these SPCs provide robust protection up to 50 kA while minimizing size (38.0 x 15.2 x 40.9 mm; L x W x H). Consequently, the MT40 series is commonly used in inverters, industrial power supplies, outdoor lighting, telecommunications systems, and surge protection devices (SPDs).

Designed for extreme electrical conditions, the MT40 series has a peak surge current capability of up to 50 kA (8/20 μs pulse) and a short-circuit current rating of up to 200 kA. The series is recognized as a UL 1449 Type 1CA component assembly, designed for use in applications with AC voltages ranging from 150 V to 550 V and DC voltages spanning from 200 V to 750 V. Additional features, such as a galvanically insulated normally open micro-switch for remote monitoring and an optional visual indicator, enhance system integration and operational safety. These MT40 components operate in temperatures ranging from -40 °C to +85 °C.

Bourns expands its surge protection portfolio with high-energy GDT devices in a compact package. (symbolic image) (Source: © Jack - stock.adobe.com)

Supporting sustainable design practices and aligning with TDK’s commitment to environmental responsibility, the MT40 series is encapsulated in a flame-retardant epoxy coating. Its RoHS compliance and lead-free materials underscore its eco-conscious profile while ensuring high reliability under demanding conditions. By combining innovation, safety, and sustainability, MT40 ThermoFuse varistors offer system designers a compact, future-proof solution for next-generation industrial and communication systems.

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