Why thermal overload relays are not always sufficient
Thermal relays mainly monitor current. However, a motor can overheat even without a significant overcurrent, for example, due to poor ventilation.
What are PTC and PT100
They are temperature sensors placed inside or near the windings.
How they provide protection
When the temperature exceeds the limit, they send a command to a relay or control system to stop the motor.
Advantage
We measure the thermal state directly rather than just the current.
