Motor Protection PTC Thermistors

ATC Semitec stock a full range of motor protection PTC thermistors with temperature switch points from 60°C to 190°C in 10K steps.  At its thermal switching point (Ts), the PTC resistance increases dramatically from a few hundred ohms to several thousand ohms over a few degrees.  Thus the PTC acts as a solid-state thermal switch and so can trigger an electronic circuit used to switch off an over-loaded electric motor, over-heated bearing or electrical appliance.

Colour-coded 26AWG PTFE leads ensure compliance to the DIN44081 standard and 3-phase motor triplet versions to DIN44082.  Owing to their very low cold impedance and step-function PTC characteristic, several motor protection PTCs can be wired in series so that multiple points (i.e. 2 or 3 motor phases) can be monitored at the same time – any one over-temperature condition triggering a motor protection relay circuit and thus thermally protecting the motor.

Call our experienced team to discuss our full range of PTC thermistors.


  • Motor winding protection
  • Bearing temperature monitoring


  • Temperature switch points: 60°C to 190°C in 10K steps
  • Max sensor voltage: 2.5VDC
  • Standard lead length: 200mm
  • Custom versions: Different lead lengths and doubles/triplets possible
Motor Protection PTC Thermistors Line Drawing