TDK Introduces Compact Thermofuse Varistors For Surge Protection Of Up To 50 kA

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. 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.

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.

Features & Applications
Main applications

• PV systems
• Industrial power supplies
• Outdoor lighting systems
• Telecommunication systems
• Surge protective device (SPD)

Main features and benefits

• Strap-terminated varistor with a thermal disconnecting system
• Compact size
• Flame-retardant epoxy encapsulation
• Short circuit current rating (SCCR) up to 200 kA acc. to UL 1449
• High peak surge current up to 50 kA
• UL 1449-recognized as a type 1CA for both AC and DC applications (file number E321126)
• Normally open micro-switch for remote indication/monitoring circuit
• Same electrode footprint of PCB for all types
• RoHS, REACH, and PFAS compliant