LST varistors make surge protection devices more robust, says Littelfuse

Based on Littelfuse’s proprietary thermally protected varistor (TMOV) technology, LST varistors have been developed by the company for Type 1 and Type 2 surge protection devices (SPDs) in residential, commercial and industrial applications.

The LST varistors incorporate both a built-in thermal disconnect function and electric arc shield. This combination provides additional robust protection to prevent catastrophic failure and fire hazard, said Littelfuse, even under the extreme circumstances of abnormal over-voltage conditions or varistor end-of-life.

The varistors are specifically designed for Type 1 and Type 2 surge protective devices (SPDs) in uninterruptible power supplies (UPS), industrial motor control, renewable energy, heating ventilation and air conditioning (HVAC) systems as well as residential, commercial and industrial buildings.

The LST varistor is claimed to have many advantages compared to other technologies currently available. Incorporating the LST into a design brings a wider operating voltage range, high surge current rating and complementary options for microswitch, explained Boris Golubovic, vice president of marketing and strategy at Littelfuse. It will also be more robust to meet the protection demands of applications, he added.

Among the benefits for the LST Varistor are its incorporation of 200kA SCCR, 20kA In, UK1449 Type 4 recognised component assembly, to meet UL1449 listed Type 1 or Type 2 standards. They also offer more options for designing remote indication/monitoring of an SPD product or system via a mechanically triggered AC and DC-rated microswitch (normally open/normally closed, pin length, two- or three-pin or no pin).

A visual tab option provides a working status indication which notifies service technicians and maintenance engineers to replace LST at end-of-life in order to continue optimal surge protection for the end-product.

The varistors have a wide operating range of up to 690V AC for the 50kA version and up to 550V AC for the 75kA version.

The LST varistor series is available in three trays containing 24 pieces each. Sample requests can be placed through authorised Littelfuse distributors worldwide.

Littelfuse is an industrial technology manufacturing company operating across more than 15 countries. Its products are found in a variety of industrial, transportation and electronics end markets.

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