Size a transformer in kVA for a given load, with headroom and diversity applied.
Connected load overstates demand because not everything runs simultaneously, so diversity is applied first. Headroom and a continuous-loading limit are then added, and the result rounded up to a standard size. Transformers loaded continuously above about 80 per cent age rapidly, so the loading figure at the chosen standard size is the number that determines service life.
Transformer Size
Required kVA = connected load × diversity ÷ power factor × (1 + headroom) ÷ max loading
Required kVA = connected load × diversity ÷ power factor × (1 + headroom) ÷ max loading Connected load overstates demand because not everything runs simultaneously, so diversity is applied first. Headroom and a continuous-loading limit are then added, and the result rounded up to a standard size.
Transformers loaded continuously above about 80 per cent age rapidly, so the loading figure at the chosen standard size is the number that determines service life.
This calculator takes 5 inputs: Connected load, Average power factor, Diversity factor, Headroom for future load, Maximum continuous loading. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.