Littelfuse Offers Two Series of Thermally Protected Varistor ProductsDesigned to Address Abnormal Overvoltage Test Requirements of UL1449
Devices in the TMOV34S Varistor Series combine a 34mm-square-format Varistor element (MOV) with high surge capability (up to 40kA) with an integrated thermally activated element. This element will open in the event of overheating due to abnormal overvoltage, limited current conditions. TMOV34S Series devices can offer quick thermal response to overvoltages in high energy circuits due to the close proximity of the integrated thermal element to the MOV body. The integrated configuration also offers lower inductance than most discrete solutions, resulting in improved clamping response to fast overvoltage transients. Some TMOV34S® devices include a monitor lead, which may be connected to signaling circuitry to indicate if the MOV has been disconnected from the circuit.
TMOV34S Series devices are designed to suppress voltage transients by clamping them to a safe level; they are also engineered to disconnect themselves from high energy circuits safely in a sustained overvoltage, limited current condition as outlined in UL1449. Because they use the same pin layout as a standard 34mm Varistor, the two-leaded version of the TMOV34S Series can be used to replace standard devices without the need for a board redesign; the TMOV34S Series also offers the added functionality of thermal protection that standard Varistor devices don’t provide.
Like the TMOV34S Series Varistor line, the 25mm-square-format TMOV25S Series Varistor line is designed for applications that require meeting the abnormal overvoltage requirements of UL1449. Devices in the TMOV25S Varistor Series incorporate a patented thermally responsive element that will open in the event of overheating due to abnormal overvoltages. This series of products is based on the Littelfuse UltraMOV Series, which meets the surge suppressor component recognition requirements of UL1449 for both cord-connected and permanently connected Surge Protection Device (SPD) end products. These devices can be wave soldered without the need for special or expense assembly processes. With a standard operating voltage range of 115VAC to 750VAC to accommodate common AC line voltages, they offer a high peak current rating of 20kA to help circuit designers meet SPD Type 1 requirements easily.
“Together, the TMOV34S and TMOV25S Varistor Series offer our customers a wider range of circuit protection options and exemplify our commitment to provide the industry’s broadest and deepest portfolio of these products,” said Littelfuse Product Manager Johnny Chang.
Littelfuse, the leader in Varistor technology, provides a comprehensive range of products and solutions that provide overcurrent protection for any electronic application. With more than 85 years of experience in building and supplying overcurrent protection products, Littelfuse is dedicated to providing application expertise and support that meets or exceeds customers’ needs.