The dry mode of the dry type transformer
is divided into natural air cooling (AN) and forced air cooling (AF). In the case of natural air cooling, the transformer can be operated continuously for a long time under the rated capacity under normal use conditions. When forced air cooling, under normal conditions of use, the output capacity of the transformer can be increased by 50%, which is suitable for intermittent overload operation or emergency accident overload operation. Since the load loss and the impedance voltage increase greatly during overload, it is in a non-economic operation state, so it should not be subjected to long-term continuous overload operation.
For natural air-cooled and forced air-cooled transformers, it is necessary to ensure that the transformer room has good ventilation capacity. When the transformer is installed in the basement or the environment with poor ventilation capacity, a heat dissipation ventilation device shall be added. The ventilation volume may be selected according to the air volume per 1 kW loss (Po+Pk) of 2 to 4 m³/min.
The new curtain fan air cooling system has low noise, uniform cooling and good effect. The size is small, the occupied space is small, and the outline size of the transformer body is not exceeded. The distribution transformer fan with small fan capacity and 2500kVA or less is only 180W~540W, and adopts 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 power distribution panel, and cannot be directly taken from the low-voltage output busbar of the transformer.