Thermal protectors

The thermal switches or temperature limiter of Alpha Therm found everywhere in applications where a reliable protection against over temperature is required. When reaching the switching temperature, the bimetal snaps in temperature switches over, breaking a contact system and thereby interrupting the electrical circuit of the device to be protected. After cooling and after reaching the reset temperature, automatically reset and thus the closing of the contact system. The circuit is thus closed again.


They are frequently used in transformers, power supply units, heaters, electric motors, solenoid valves, fan, water heater, ballasts, alarm systems, electronic circuits, power transistors, and many more.

UK Series


  • AC 250V / 2A
  • 50°C...145°C
  • NC
  • Automatic reset
  • Plastic case
  • Solid or Stranded wire
Thermoschalter UK Serie

BW-D Series


  • AC 250V / 6A
  • DC 24V / 5A
  • 40°C...145°C
  • NC or NO
  • Automatic reset
  • Plastic- or insulated metal case
  • Solid or Stranded wire
  • Flat design (3mm)
Thermoschalter UK Serie

ST06 U1 Series


  • AC 250V / 10A
  • 60°C..180°C
  • NC or NO
  • Automatic reset
  • With shrink cap insulation
  • Stranded wire
  • Pressure resistant

ST01 U2 Series


  • AC 250V / 5A
  • 60°C...180°C
  • NC or NO
  • Automatic reset
  • Without insulation
  • Stranded wire
  • Pressure resistant

ST01 U3 Series


  • AC 250V / 5A
  • 60°C...180°C
  • NC or NO
  • Automatic reset
  • Without insulation
  • Without wire
  • Pressure resistant
  • Clamping contact

ST01 U4 Series


  • AC 250V / 5A
  • 60°C...150°C
  • NC or NO
  • Automatic reset
  • Epoxy insulation
  • Stranded wire
  • Pressure resistant

ST01 U5 Series


  • AC 250V / 5A
  • 60°C...180°C
  • NC or NO
  • Automatic reset
  • With transparent shrink cap insulation
  • Stranded wire
  • Pressure resistant

ST01 U6 Series


  • AC 250V / 5A
  • 60°C...180°C
  • NC or NO
  • Automatic reset
  • Plastic case
  • Stranded wire
  • Pressure resistant
  • Screw-on mounting

ST01 U7 Series


  • AC 250V / 5A
  • 60°C...180°C
  • NC or NO
  • Automatic reset
  • Insulated thread case
  • Stranded wire
  • Pressure resistant
  • With M4 x 6mm thread

ST01 U9 Series


  • AC 250V / 5A
  • 60°C...180°C
  • NC or NO
  • Automatic reset
  • Plastic case
  • Stranded wire
  • Pressure resistant
Thermoschalter Q Serie

ST01 U8 Series


  • AC 250V / 5A
  • 60°C...180°C
  • NC or NO
  • Automatic reset
  • Plastic case
  • Solid wire
  • For PCB-mounting
  • THT-Pitch 5,08mm

Q Series


  • AC 250V / 2,5A
  • 40°C...150°C
  • NC
  • Electric self-holding
  • Plastic case
  • Solid or Stranded wire
Thermoschalter UK Serie

B12 Series


  • AC 250V / 10A (max. 30A)
  • 70°C...190°C
  • NC or NO
  • Automatic reset
  • Sintered
  • Stranded wire

Mounting Bracket


  • For mounting of the UK Series, ST-22 Series, BW-D Series,
    Q Series and much more
  • Spring steel
  • 3,5mm hole
  • Drummed and hardened
  • Thick layer passivated

ST01 U1 Series


  • AC 250V / 5A
  • 60°C...180°C
  • NC or NO
  • Automatic reset
  • With shrink cap insulation
  • Stranded wire
  • Pressure resistant

ST06 U2 Series


  • AC 250V / 10A
  • 60°C..180°C
  • NC or NO
  • Automatic reset
  • Without insulation
  • Stranded wire
  • Pressure resistant

ST-22 Series


  • AC 250V / 7A
  • DC 48V / 3A
  • 50°C...145°C
  • Öffner
  • Automatic reset
  • Plastic case
  • Solid or Stranded wire
Thermoschalter UK Serie

BW-C Series


  • AC 250V / 2A
  • DC 24V / 3A
  • 30°C...150°C
  • Current sensitive
  • NC or NO
  • Automatic reset
  • Plastic case
  • Stranded wire
  • Very flat design (2,4mm)
Thermoschalter UK Serie

ST07  Series


  • AC 250V / 10A
  • AC 120V / 22A
  • DC 16V / 20A
  • 55°C ... 180°C
  • NC
  • Automatic reset
  • Overload protection caused by current sensitivity
  • axial or radial design


α Therm


Alpha Therm GmbH - Your specialist for temperature-limiting

safety components, sensor elements or sensors

© 2018 Alpha Therm GmbH

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Phone: +49 6202 / 575688 - 0

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