The cooling methods of dry-type test transformer are divided into natural air cooling (AN) and forced air cooling (AF). Under normal operating conditions, the transformer can operate continuously at rated capacity for a long time with natural air cooling. With forced air cooling, under normal operating conditions, the output capacity of the transformer can be increased by 50%, suitable for intermittent overload operation or emergency overload operation; however, due to the significant increase in load loss and impedance voltage during overload, it is in a non-economic operating state, so it should not be subjected to long-term continuous overload operation.
For transformers with natural air cooling and forced air cooling, it is necessary to ensure good ventilation in the transformer room. When the transformer is installed in a basement or in an environment with poor ventilation, additional heat dissipation and ventilation devices must be installed. The ventilation volume can be selected based on 2 to 4 m3/min of air volume per 1kW loss (Po+Pk).
The new curtain-type fan air cooling system has reduced noise, uniform cooling, and good effect; it is small in size, occupies little space, and does not exceed the overall outline dimensions of the transformer body; the fan capacity is small, for distribution transformers below 2500kVA, the fan power is only 180W to 540W, and it uses single-phase AC220V power supply. However, it should be noted that this power supply should be taken from the circuit breaker in the low-voltage MCC or PC distribution panel, and not directly from the low-voltage outgoing busbar of the transformer.
