Power transformer temperature switch application case

Power transformers play an extremely important role in the safety of most medical electrical equipment. If the equipment transformer fails during operation, the temperature rise of the transformer winding will be too high, exceeding the maximum temperature that its material parts can withstand, which may cause the transformer insulation failure, causing electric shock and fire hazards. Therefore, attention should be paid to the thermal protection of the transformer.

Our customer is a transformer manufacturer. In order to help customers choose the most suitable temperature switch, we have done a simulation experiment according to the customer's use environment: short-circuit experiment and overload experiment. In the short-circuit experiment, we measured the temperature change value of the winding, and based on other data, we can know which part of the protection device works, and then carry out the overload test based on this result. When carrying out the overload experiment, continue to increase the current to the temperature switch until the maximum value of the temperature switch inactive is measured. The most suitable temperature protection parameters are obtained through these two experiments. It should be noted that there is a certain deviation between the winding temperature when the temperature switch operates and the nominal operating temperature of the temperature switch. This is related to the reaction speed, accuracy and placement position of the temperature switch.

Power transformers commonly use self-recovery temperature switches, such as the HCET-A miniature temperature switch, which switches the circuit on and off by sensing the temperature, thus playing a role in thermal protection. The operating temperature error is generally ±5°C, the reset temperature is generally 20°C lower than the operating temperature, and the error is about ±10°C.

When selecting the temperature switch of the power transformer, attention should be paid to selecting the specifications suitable for the working voltage and working current of the transformer. When installing, try to place it at the innermost end of the winding and close it closely. When welding, pay attention to the good connection of the lead wire to prevent the virtual connection from generating heat and affecting the normal operation of the temperature control switch.