SEKI ST-30 Bimetal Thermal Switch

The SEKI ST-30 is the smallest, encapsulated bimetallic thermal cut-out in the ST series, allowing for easy integration into numerous products like electric motors and transformers.  They could also be used in battery packs and battery chargers.

The ST-30 uses a snap action bimetal strip that is factory calibrated to any setting (in 5K steps) from 50℃ to 150℃.  The bimetal disc snaps open at its predetermined setting and then closes again on cooling, thus protecting the appliance from over-temperature and/or over-current conditions.

The SEKI ST-30 is housed in a PBT resin case with an epoxy seal ensuring long-term integrity and reliability.  The standard lead-wires are 70mm long XLPE but longer versions and short bare wires can be supplied for volume applications.


  • Electric Motors
  • Battery Chargers and Packs
  • Transformers
  • Power Supplies
  • Heating Pads
  • Solenoids
  • LED Lighting


  • Snap Action with Automatic Reset
  • Superior Heat Response
  • Contact Rating: 5A/250V AC (10,000 cycles)
  • Factory calibrations from 50℃ to 150℃
  • UL/cUL, VDE, CQC, KC
  • PBT Resin Case with Epoxy Sealing
  • IP45 rating
cost-effective, reliable range of thermal protectors and thermostats from ATC Semitec SEKI ST-30 Thermal Cut-out Drawing