TDK presents two new series of ThermoFuse varistors that are equipped with monitor outputs for monitoring purposes. The MT25 series (B72225M*) currently covers a voltage range from 150 VRMS to 385 VRMS, and its maximum surge current capability is 20 kA with a pulse shape of 8/20 µs in accordance with IEC IEC61643-11. With dimensions of 25 x 28 x 14 mm, the fully encapsulated protective components are very compact. Their monitor outputs are optionally available with or without galvanic isolation.
The MT30 series (B72230M*) includes types designed for voltages from 150 VRMS to 750 VRMS. Their maximum surge current carrying capacity is 25 kA with a pulse shape of 8/20 µs in accordance with IEC IEC61643-11, and the dimensions are 34 x 28 x 14 mm. The monitor outputs of these varistors are designed with galvanic isolation.
The specially developed square disk varistors are connected in series with a thermal protection element. The design of the protective element is patented. In the event of continuous overvoltage and thus heating of the varistor, this fuse responds and disconnects the varistor from the circuit with a high degree of reliability. This prevents potential damage to the circuit board or components mounted close to the varistor. In addition, disconnection from the mains protects against thermal runaway. Thanks to their high thermal load capacity and the use of flame-retardant material for the housings, the ThermoFuse varistors in the MT25 and MT30 series meet the requirements of flammability class UL 94 V-0 and are listed in the UL 1449 4th Edition standard. The main applications are photovoltaic inverters, high-performance industrial power supplies and inverters as well as power supplies for lighting systems and telecommunications equipment.
