To choose the right transformer for an 800KW equipment, we need to consider the power factor and the actual load demand. When the power factor is assumed to be 0.8, the apparent power of the equipment is calculated as follows:
800KW/0.8=1000KVA
So a basic recommendation is to select a transformer with a nominal value of 1000KVA. However, the actual selection needs to take into account the efficiency of the transformer and the load profile. According to the Power Engineering Design Guide, for a single transformer supplying power and a relatively smooth load, the recommended load factor is around 85%, which means that a 1000KVA transformer may not be sufficient to meet 85% of the load, and a larger capacity should be selected, such as 1176KVA or more.
In particular, if the equipment is a single motor, the transformer capacity should be increased appropriately to accommodate this instantaneous load as the current increases significantly during starting. In addition, if there is a three-phase imbalance in the equipment, the calculation of transformer capacity also needs to take into account the unevenness of the load on each phase to prevent overloading.
Therefore, these factors should be considered when selecting a transformer to ensure stable operation of the equipment and to avoid wasting excessive capacity. In practice, transformers higher than 1176KVA may be required to cope with motor starting and unbalanced loads.