Temperature Control with PT100 as a protective measure for Electrical Motors

Monitoring the temperature of an electrical machine or system, with PT100 for example, is one of the most important factors when it comes to safeguarding these systems. In addition to over-current monitoring, which is intended to limit excessive current, it is vitally important to control the temperature of motors. High temperatures inside machines can cause all types of damage, including thermal wastage. High loads and stress on cables and bearings helps to cause this type of deformation over time.

Measuring and Recording Temperature Values with PT100

Basically, several options are available for recording different temperatures. The easiest way is to use PT100 thermistors or PTC thermistors. However, temperatures can also be recorded by using laser or infrared measurements.
The PT100 thermistor is a variable electrical resistor with a nearly linear load (only the linear range is used), which changes its value whenever the temperature fluctuates. Changes in thermistor resistance can be used to determine current or voltage changes. Changes in resistance can be used to make a resistance curve which indicates the corresponding temperature. Today this entire process happens automatically in circuits or programs. Thermistors are divided into hot and cold leads, which are known as NTC (PT100) and PTC thermistors.

Using an Frequency Inverter with PT100 to prevent excessive Motor Temperatures

Technicians and installers often use external cooling systems as a solution for high temperatures. However, this depends on what exactly is causing the overload and the associated increase in temperature. This increase often occurs with large currents. Optimal control and a PT100 can be used to counteract this. This type of scheme may be implemented by controlling the rotational speed. The rotational speed or cyclic frequency of the AC power supply in a three-phase motor changes and thus changes the speed and load of the engine. This type of arrangement with a PT100 and a frequency inverter is ideal for reducing stress and consequently, lowering the temperature of an engine.

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