In practical application, transformers are used to deliver electric power from the power source or generators to the user. Transformers transfer electricity from one electrical circuit to another, through mutual electromagnetic induction. They work by increasing or decreasing alternating current voltage in circuits. Power of one voltage is transformed into the power of another voltage level. The reason for this is because it is easier for high voltages to travel long distances, but when delivering the electric power to the user, less voltage is a lot safer and easier. A typical example would be high voltages of about 7,200 volts which are transformed to the more suitable levels of 220-240 volts typically used to power electric appliances and equipment in residential homes and businesses.
Heat is a normal occurrence in transformers as the regular operation of any transformer naturally generates waste heat. Coolants are provided to dissipate this excess heat, although air circulation may be sufficient to cool smaller transformers of up to a few kilowatts. For larger transformers, oil is often used as a coolant, while larger, high-powered transformers are equipped with additional cooling equipment such as fans.
Despite the presence of coolants, however, transformers can and sometimes do get overheated. There are different possible reasons why a transformer could overheat, and the solution should be based on the cause of why excessive heating happened in the first place. Below are some of the possible causes for excessive heat in transformers, and the recommended solution for each:
Each transformer has a kVA rating, and kVA ratings are dependent on temperature. If the total load exceeds the transformer’s kVA rating, the transformer could overheat.
As a solution, you could reduce the size of the load or replace the transformer with a larger one, with an increased maximum load and additional cooling features such as fans.
- Excessive ambient temperatures
Transformer ratings also provide for ambient temperatures, and when this is exceeded, a transformer may overheat.
The solution in such a situation is to relocate the transformer to a different area with lower ambient temperatures, or if possible, the ambient temperature at the primary location must be reduced. Small rooms, for instance, could be equipped with proper ventilation to reduce the room temperature.
- Excessive or sustained airflow by excessive winds or fans
You might think that high winds in the environment would make for cooler temperatures for the transformer. But it can also happen that the high winds traveling horizontally may disrupt the cooling fans of the transformer so that they can no longer function well, thus causing the transformer to overheat.
To prevent this from happening, you can either block the wind or relocate the transformer to an area that is less prone to high winds.
- Misaligned or broken transformer fans
This is a breakdown of the original cooling provision for the transformer and can be resolved by simply fixing the fan or replacing them.
- Improper Input Voltages
Check that the taps are set correctly for the input voltage. If there is continuous overvoltage or undervoltage, a difference of as low as 5-10% may cause overheating.
- Check the no-load current
The no-load current values vary depending on transformer efficiency, but mostly they are less than 2-3% of the total kVA. If it is higher, there may be damage to the core or the coils. The transformer should be returned to the manufacturer so that the core and coils can be properly checked. If there was a short between the core and coil, then the transformer will have to be repaired or replaced.
- Flames or Smoke
Sometimes the issue goes way past excessive temperatures and right to visible smoke and flames. This may be a sign that the transformer’s insulation may have been damaged and needs to be repaired or replaced.