EPCOS ThermoFuse™ Varistors – Intrinsically-safe Over-voltage Protection

The new T series of ThermoFuse™ varistors is a housed component, consisting of a disk varistor in series with a thermally coupled fuse. If the varistor overheats, the thermal fuse activates and disconnects it from the power circuit, thus preventing the occurrence of fires, in the worst case. This increases reliability and protects the
equipment. Both the housing and the coating of the varistor are made of flame-retardant material.

The ThermoFuse™ varistor has three terminal wires. Two are connected to the active lines while the third terminal can be used for status signalling. The T series lineup currently comprises types that feature disk varistors with diameters of 14 mm and 20 mm and are designed for maximum operating voltages of between 130 and 1000 VRMS. The new ThermoFuse varistors can withstand surge currents of up to 10.000 A (8/20 μs) and absorb up to 410 J (2 ms).

Key Features

• Terminal wires in line for easy assembly
• Rated voltages of 130 to 1000 VRMS
• Robust and flame-retardant housing for physical protection of adjacent components
• 5 mm spring opening distance for reliable disconnection from power circuit
• Disconnection function according to limited current abnormal overvoltage test in UL 1449, 3rd edition, section 39.4, and as per thermal stability test in IEC 61643, edition 1 (2011), section
• T14/ T20 pin compatible for same PCB layout and different surge current levels (130 up to 420 V)
• Flammability according to UL 94 V-0

ThermoFuse™ Varistors, T Series


Household appliances

Lighting applications

Power supply units

Communication and data systems

Inverters in solar power systems

Transient voltage surge suppression (TVSS)