Industrial Engineer · phase 14 of 16
Motor Thermistor / PTC
Temperature-sensitive device embedded in a motor and connected to the drive or protection relay.
The Explain card
- Plain English
- A thermistor is a temperature sensor embedded in the motor windings. A PTC type has a resistance that rises sharply when the winding reaches its limit, and the drive or a relay reads that change as a trip.
- Example
- A motor wired with a PTC in its windings runs at low speed under heavy load. The winding heats past its rating, the PTC resistance jumps, and the drive trips on motor overtemperature.
- Why it matters
- The electronic overload model guesses the motor temperature, and the thermistor measures it. On motors that run slow, run hot or sit in bad ambient, the sensor catches what the model misses, and it needs its own input on the drive.
- Hook
- A thermometer inside the winding, telling the truth.
Where it sits in the deck
Phase 14: VFD Safety, Faults, and Diagnostics
What a drive does when it trips, what the fault codes are telling you, and how safe torque off stops the motor without killing the panel.
