High power transformers are vital components within power supply systems and work to either ‘step up’ or ‘step down’ an incoming power supply. This is done by a precise relationship between the number of turns on the primary and secondary coils. Put simply, a transformer converts energy at one voltage level to energy at another voltage level. Heat generated in dry transformers must be dissipated over the surface of the coil. A combination of transformer cooling fans are ideally suited for this purpose. Our range of axial and centrifugal fans manufactured by Rosenberg, help to remove the dissipated heat and, simultaneously, use the ambient air (outside the transformer) to cool down the transformer.
Transformers do not have any moving parts but they do suffer losses, these are called either ‘copper losses’ or ‘iron losses’. Copper loss is the electrical power lost in heat as a result of circulating the currents around the transformers copper windings, this is often referred to as hot spots and can have a negative impact on the life span the transformer. Hysteresis, or Iron loss, is the lagging of the magnetised iron molecules within the core. The magnetised iron molecules are responding to the alternating magnetic flux generated by the AC input current. This lagging (or out-of-phase) condition is due to the fact that it requires power to reverse magnetic molecules; they do not reverse until the flux has attained sufficient force to reverse them.
The higher the capacity of the transformer, the higher the losses and resultant heat generation. This means the temperature of the windings and the core increase. Thus, an effective cooling technique needs to be implemented to prevent the system over heating and ultimately failing.
The following advantages result from efficient transformer cooling via forced air circulation using fans:
Both centrifugal and axial fans can work together as per the diagram. In this case, a centrifugal fan is pulling warm air down, extracting it away from the transformer whilst an axial fan provides cool supply air. There can be multiple configurations like this depending on the air volume and pressure requirements. Ensuring the complete control of the operation temperature reduces the risk of overheating and will prolong the life of the transformer. System failures due to overheating result in a loss in productivity which must be avoided at all costs in applications distributing a constant supply of electrical power.
Our Centrifugal fans particularly suit compact transformer units with high pressure losses through the cooling coils, as this demands a higher-pressure development from the fan than larger units. There will be a similar total air flow requirement in both sizes of transformer as the heat generation will be alike.
Our Axial fans are suited to larger transformer units with lower pressure loss as they require a lower pressure fan. They will provide a similar air flow to centrifugal fans but at a lower pressure development.
Our DKNR range of centrifugal fans with free running impellers:
Our AKSD / AKFD ranges of axial fans: