A component protects electronic systems from power surges. It helps improve safety in power, industrial, and communication systems.
TDK Corporation has introduced the MT40 series of ThermoFuse varistors, designed to protect electronic systems from high-energy surges. The components can handle peak surge currents of up to 50 kA and short-circuit currents up to 200 kA while maintaining a compact size of 38.0 × 15.2 × 40.9 mm (L × W × H). The devices combine a metal oxide varistor with an integrated thermal disconnection system to improve safety during fault conditions.
The MT40 series is recognized as a UL 1449 Type 1CA component assembly. It supports AC operating voltages from 150 V to 550 V and DC voltages from 200 V to 750 V. The devices also include a galvanically insulated normally open micro-switch for remote monitoring, along with an optional visual indicator to show device status. They are designed to operate in temperatures ranging from –40 °C to +85 °C.
The compact design is achieved using a patented overmolding technology that integrates the varistor and thermal protection in a single package. The components are encapsulated in flame-retardant epoxy and use lead-free materials, meeting RoHS requirements.
Key features of the MT40 series include:
- 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
These varistors are used in several systems that require surge protection. Key applications include photovoltaic (PV) systems, industrial power supplies, outdoor lighting infrastructure, telecommunication systems, and surge protective devices (SPDs). In such environments, electrical equipment is often exposed to lightning strikes, switching transients, and other high-energy disturbances. The MT40 series is designed to limit these surges and protect connected electronics.
