Thermal modeling and measurement of a transformer using pcb sensor sheet
Hassan Rouhi · Aaltodoc (Aalto University) · 2019
A transformer is a device that usually has at least two windings and converts voltage from a level to another level without changing the frequency. Transformers are used widely in the power networks and due to their high price, it is extremely crucial to evaluate their losses, the value of the temperature rise (for protecting the insulation) and their efficiency. The temperature above the limit may leads to serious damage in the transformer components. Traditional way of obtaining the total power loss in a transformer is subtracting the output power from the input power with the help of a power analyzer. But high harmonics can affect the quality of the measurements and as a result, leads to inaccurate power loss calculation. This thesis aims to develop a thermal model in COMSOL and find the value of temperature rise in the transformer and compare it with the temperature rise in the lab. The losses of the transformer can be calculated inversely from the value of the temperature rise. The measurements in different conditions and at different frequencies are done in the lab and the core loss obtained by the method discussed in chapter 3. Secondly, the electromagnetic model of the transformer in COMSOL is developed to obtain the core loss of the transformer and compare it with the core loss obtained from the measurements. Finally, the thermal model of the transformer is developed in COMSOL and the values of the core loss obtained from the electromagnetic model injected into the thermal model for estimating the temperature rise in the transformer. The temperature rise verified by the temperature rise measurement in the lab. Two PT-100 temperature sensors are used for the measurements in the lab. The sensors are located in the middle of the transformer and the temperature was read by Agilent 34970 A. The results obtained from both the electromagnetic model and thermal model are in good agreement with the results from the measurement.