TDK MT25/MT30 series ThermoFuse® resistors are equipped with monitor outputs and integrated thermal protective components for overvoltage protection.
The MT25 series (B72225M*) currently covers a voltage range from 150VRMS to 385VRMS, and its maximum surge current capability is 20kA at a pulse form of 8/20 µs, according to IEC 61643-11. With dimensions of 25mm x 28mm x 14mm, 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 150VRMS to 750VRMS. Its maximum surge current capability is 25kA at a pulse form of 8/20 µs according to IEC 61643-11, with dimensions of 34mm x 28mm x 14mm. 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.
