Description

Thermal motor protection without a temperature probe is an inverter function that can protect motors without temperature probes (e.g. PTC thermistors, bimetallic switches) against overheating. The level of protection is similar to that of a thermal overload relay.

Thermal motor protection without a temperature probe has the following characteristics:

• Motor protection takes reduced cooling into account, especially at lower speeds.
• Motor protection does not take insufficient cooling conditions and increased ambient temperature into account.
• In the event of overloads in the low speed range, increased motor winding temperatures may occur which may damage the motor winding or lead to premature aging of the motor.
• The cooling of the motor is stronger at low temperatures. For motors with a temperature probe, the temperature probe measures an overtemperature only at increased motor utilization and switches off the motor. This increased motor utilization is not possible with thermal motor protection without a temperature probe.

This means that thermal motor protection without a temperature probe only represents basic protection.