Our company is planning to shift to a new site and I was tasked with finding out the required kVA power to install a PMT. I have the kW ratings, amperage, voltage and power factor for all machines and other equipment in use. Using this as a reference, I found the reactive power for all machines, then summed up the total kW ratings, summed the kVAR ratings, and used the power triangle to get the total real power.
Is this method correct? Is it 'accurate'? I was told it is incorrect and I would have to find the real power for the single-phase and three-phase machines separately, and divide the single-phase total power by 3 because it goes into three-wires. This is the first time I am dealing with a real-life design problem so help would be appreciated. If any other details are required please let me know.
Best Answer
If you just add up the rating plate values for every piece of equipment in the building, you will end up with a figure that far exceeds what you actually use. That's because you haven't allowed for "diversity". In practice, nobody turns every bit of equipment on at the same time, nor is everything running at full power all the time.
You would be better off buying a clamp meter, and clamping it around each of the phases running into your current building in turn, to see what you actually use. Then add a bit of safety margin on top.