Industrial Engineer · phase 14 of 16 · noun
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.
Word knowledge
How the word is built, where it came from, and what it sits beside in memory.
In a sentence
During commissioning, the technician verifies that the motor thermistor trips the VFD when the PTC input reaches its threshold.
Why these words
- motor Latin motor, mover specifies the equipment associated with the thermistor
- thermistor English blend of thermal and resistor serves as the head noun of the phrase
Where it came from
- Origin
- English technical phrase using motor, from Latin motor, and thermistor, coined from thermal plus resistor
- Entered the language
- 1940s
- What changed
- Motor shifted from a general mover to a machine term, while thermistor became the name for resistive temperature-sensing components; PTC abbreviates positive temperature coefficient.
How it is spelled
- Pattern
- The phrase is written as the open compound motor thermistor.
- Pattern
- Thermistor keeps the Greek-derived therm- spelling and the -istor ending found in several electronic component names.
- Breaks the pattern
- Thermistor is a compressed blend that omits letters from both thermal and resistor.
Spelled like
- resistor
- varistor
- transistor
Broken into chunks
-
motor
- motion
- motive
- motorize
-
therm
- thermal
- thermostat
- thermocouple
-
istor
- resistor
- varistor
- transistor
What it sits beside
Same subject
- VFD
- motor overload relay
- winding temperature
- PTC input
- RTD
Same shape
- resistor
- varistor
- transistor
motor temperature devices
- PTC thermistor
- NTC thermistor
- RTD
temperature coefficient labels
- PTC
- NTC
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.
