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Trip Amplifiers for Temperature Measurement [Application Report]

Isolator modules with trip relays offer an economic solution for control of electrical machines


Electrical machines perform basic functions in automation technology, e.g., as drives for worm conveyors, conveyor belts, and pumps. They must be reliably monitored and controlled due to potentially significant consequences in the event of a fault. Monitoring approaches are required that can detect faults and trigger corrective measures. This task does not necessarily have to be performed by a process control system or PLC. An economic solution can be implemented by using isolator modules with trip relays.


The objective of a monitoring concept is to prevent failure, overload, or malfunction, as well as reliably control safety-relevant parameters and shut down the affected device in the event of a fault. This allows danger to persons and the environment, damage to the machine, and a system shutdown to be prevented.


With temperature converters such as KFD2-GUT*, switch signals are available on the module output without having to rely on a central controller
With temperature converters such as KFD2-GUT*, switch signals are available on the module output without having to rely on a central controller

Isolator modules must be used between field level and the controller due to long and interference-prone signal paths – either as isolated barriers to protect the hazardous area against too high an energy input, or as signal conditioners for non-hazardous areas. If GUT temperature converters such as KFD2-GUT* with limit value outputs that can be parameterized are used as isolator modules, switch signals are already available on the module output without having to rely on a central controller.


When measuring temperatures on electrical machines, the readings from the stator, bearings, and surfaces are very relevant. For example, they reflect anomalies in induction currents, lubricant pressure, or cooling. If the electrical machine is used as a drive for a pump, monitoring the temperatures of the pumped fluids can be an effective way to prevent the drive from becoming overloaded.

If fluids have a solidification point above the ambient temperature, monitoring of the temperature can be used to delay the start-up of the pump until the viscosity of the fluid reaches operating level. The transmitted signals are continuously monitored by the module for under- or overruns of selectable trip values. If the set values are reached, defined processes are triggered: In the most basic of instances, this is a shutdown of the affected component.

At a glance

  • Temperature converters with trip values allow the temperature to be monitored without having to intervene in the control system, for example if the trip points
  • These are suitable for all types of sensors used to measure temperature (thermocouples, resistance thermometers, potentiometers)
  • The module is part of the K-System product family, which includes additional trip amplifiers. This means virtually all critical parameters (rotation speed monitoring synchronization monitoring, transimtter power supply with programmable high or low alarm) can be monitored using modules from the same system