Passives

Power varistor series operates at high temperatures

15th November 2016
Alice Matthews

A varistor series has been introduced by Littelfuse that is designed for high power applications and can operate at ambient temperatures up to 125°C with 2,500V isolation voltage. The HMOV Varistor Series’ high operating temperature is an advance made possible through the use of a silicone coating technology.

Competitive epoxy-coated varistor designs are typically limited to maximum temperatures of just 85°C. The products were announced at the company’s booth during electronica, the international trade fair for electronic components, systems and applications, held 8th to 11th November 2016, at the Munich Trade Fair Centre. 

The HMOV Varistor Series’ high operating temperature makes it possible to reduce end-product production costs by eliminating the need for an additional heat sink or potting process. The series has a high operating temperature, high surge current absorption of up to 10kA (8/20µs), reliability confirmed by a 1,000-cycle thermal stress test, and high isolation voltage (2,500V). The series is available in disc diameters of 10, 14 and 20mm.

The HMOV Varistor Series is best-suited for high temperature and high power DC or AC applications including:

  • Industrial automation controls
  • Solar power inverters
  • Security systems
  • Fire alarm and smoke detectors
  • Smart meters
  • Outdoor LED lighting
  • Base Transceiver Station (BTS) power supplies
  • Harsh environment/outdoor power supplies

“The HMOV Varistor Series combines the ability to operate at ambient temperatures up to 125°C with superior surge current handling capability,” said Johnny Chang, Littelfuse Product Manager for the HMOV Series Varistor line. “That allows it to provide the safest, most reliable, energy-efficient and cost-saving circuit protection solution available for DC and AC applications that require higher power in extremely hot indoor and outdoor environments.”

The HMOV Varistor Series offers these key benefits:

  • High operating temperature of 125ºC allows the high power end products into which it’s built to run safely at higher ambient temperatures and saves costs by eliminating the need for an additional heat sink or potting process.
  • High isolation voltage (2,500V) eliminates the need for additional insulation material and helps minimise PCB size by reducing the space required between the varistor and other components on the board.
  • Thermal shock testing (1,000 cycles from -55 to 125ºC) offers enhanced reliability that can extend the lifetime of the end products.
  • Meets UL 1449 and IEC 60950-1, which supports worldwide compliance for end products.

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