TDK launches compact ThermoFuse varistors for 50 kA surge protection
TDK has unveiled a new generation of surge protection components aimed at industrial and infrastructure electronics. The company’s MT40 series of ThermoFuse varistors combines high surge capability with a compact form factor and integrated safety features.
The components are designed to deliver robust protection in demanding electrical environments while keeping system size under control. For engineers designing power and infrastructure equipment, this development could simplify surge protection design while improving reliability and monitoring capabilities.
Compact design with high surge capability
The new MT40 series integrates a varistor with a thermal disconnecting system in a single compact package measuring 38.0 x 15.2 x 40.9 mm. Using patented overmolding technology, the devices are able to handle peak surge currents of up to 50 kA using the standard 8/20 µs pulse waveform.
In addition to high surge performance, the components feature a short-circuit current rating (SCCR) of up to 200 kA according to UL 1449 requirements. This combination of surge capability and fault protection targets applications exposed to extreme electrical transients.
TDK says the MT40 series is recognized as a UL 1449 Type 1CA component assembly, enabling use in both AC and DC surge protection applications. The devices support AC voltages from 150 V to 550 V and DC voltages between 200 V and 750 V.
Built for industrial and infrastructure electronics
Typical applications for the MT40 series include PV systems, industrial power supplies, outdoor lighting infrastructure, telecommunications equipment, and surge protection devices (SPDs). In these systems, protection components must withstand high surge currents while maintaining safe operation and system availability.
To support system monitoring and integration, the devices can include a galvanically insulated, normally open micro-switch that enables remote indication and monitoring. An optional visual indicator can also signal device status, allowing easier maintenance in field installations.
The varistors are designed to operate in temperatures ranging from -40°C to +85°C, making them suitable for outdoor and industrial environments.
Safety and sustainability considerations
TDK also emphasizes safety and environmental compliance in the MT40 design. The components are encapsulated in a flame-retardant epoxy coating, helping improve fire safety under fault conditions.
The series is compliant with RoHS, REACH, and PFAS requirements and uses lead-free materials. According to the company, these characteristics align with its broader sustainability goals while ensuring reliability in demanding electrical applications.
By combining high surge capability, monitoring features, and compact packaging, the MT40 ThermoFuse varistors are positioned as a protection solution for next-generation industrial, renewable energy, and communications systems.
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