TDK Electronics · TDK Europe

October 15, 2020

ThermoFuse® varistors: TDK releases new series of varistors for overvoltage protection and enhanced monitoring


TDK Corporation (TSE: 6762) presents two new series of ThermoFuse® varistors, which are equipped with monitor outputs and integrated thermal protective components for overvoltage protection.

The MT25 series (B72225M*) currently covers a voltage range from 150 VRMS to 385 VRMS, and its maximum surge current capability is 20 kA at a pulse form of 8/20 µs, according to IEC 61643-11. With dimensions of 25 x 28 x 14 mm, the completely encapsulated protective components feature a particularly compact design. Their monitor outputs are optionally available with or without electrical isolation.

The MT30 series (B72230M*) includes types, which are designed for voltages from 150 VRMS to 750 VRMS. Its maximum surge current capability is 25 kA at a pulse form of 8/20 µs according to IEC 61643-11, with dimensions of 34 x 28 x 14 mm. The monitor outputs of these varistors are designed with electrical isolation.

The new ThermoFuse varistors are specially developed quadratic disk varistors, which are connected in series with a patented thermal protective component design. In the case of a persistent overvoltage and therefore heating of the varistor, the fuse is activated and separates the varistor from the circuit with a high level of reliability, preventing potential damage to the PCB or the components installed in the varistor’s vicinity. What’s more, disconnection from the mains protects against a thermal runaway.

Thanks to their high thermal resistance and use of flame retardant materials for the housing, the ThermoFuse MT25 and MT30 series varistors meet the requirements of flammability rating UL 94 V-0. They are listed in the UL 1449 standard 4th Edition.

These varistors’ main applications include photovoltaic inverters, powerful industrial power supplies and inverters, as well as power supplies for lighting systems and telecommunications systems.

Main applications

  • Photovoltaic inverters
  • Powerful industrial power supplies
  • Inverters
  • Power supplies for lighting systems and telecommunications systems

Main features and benefits

  • Wide voltage range from 150 VRMS to 750 VRMS
  • High surge current capability of up to 25 kA (8/20 µs)
  • Monitor outputs with or without electrical isolation
  • Complete encapsulation
  • Particularly compact design

Further information on the products can be found under  

About TDK Corporation

TDK Corporation is a world leader in electronic solutions for the smart society based in Tokyo, Japan. Built on a foundation of material sciences mastery, TDK welcomes societal transformation by resolutely remaining at the forefront of technological evolution and deliberately “Attracting Tomorrow.” It was established in 1935 to commercialize ferrite, a key material in electronic and magnetic products. TDK's comprehensive, innovation-driven portfolio features passive components such as ceramic, aluminum electrolytic and film capacitors, as well as magnetics, high-frequency, and piezo and protection devices. The product spectrum also includes sensors and sensor systems such as temperature and pressure, magnetic, and MEMS sensors. In addition, TDK provides power supplies and energy devices, magnetic heads and more. These products are marketed under the product brands TDK, EPCOS, InvenSense, Micronas, Tronics and TDK-Lambda. TDK focuses on demanding markets in automotive, industrial and consumer electronics, and information and communication technology. The company has a network of design and manufacturing locations and sales offices in Asia, Europe, and in North and South America. In fiscal 2020, TDK posted total sales of USD 12.5 billion and employed about 107,000 people worldwide.

Media Contact

Christoph Jehle TDK Electronics AG Munich/Germany Phone +49 89 54020-2441 Get in contact
Debbie Martin TDK Electronics Inc. Fountain Hills, AZ/USA Phone +1 480 836-4104 Get in contact
Candido Dall'Agnoll TDK Electronics do Brasil Ltda. São Paulo/Brazil Phone +55 51 3484-7007 Get in contact
Himalaya Baghel TDK India Private Limited Mumbai/India Phone +91 12 04 50 58 42 Get in contact
Stella Suen TDK Electronics Hong Kong Limited Phone +852 3669-8224 Get in contact
Vincent Gaff Tronic's Microsystems SA Phone +33 4 76 97 29 60 Get in contact

Stay Connected

Press Newsletter

We would be happy to keep you informed via e-mail. Please note that this service is for journalists only.


Social Media