So we’re talking talking about transformers, which are commonly used to step down from the ver

So we’re talking talking about transformers, which are commonly used to step down from the very high voltages present on utility lines to the lower voltages available in a commercial or residential setting. In this scenario, we’re going from a 20 kV line voltage to a 240 V local voltage. We’ll assume that the 240 V off that transformer is supplying 15 buildings with a supply of 150 A each. What kind of turns ratio is needed for this transformer, and how much power does it need to be rated for?The turns ratio will be the same as the ratio of the voltages between the primary and secondary coils. In this case, it works out to 0.012.To figure out the power rating, we need to know current and voltage. We know what that is on the secondary side, but the primary side is where it’s really going to be a problem. We know there’s 20 kV on that side, but we don’t know the current. Fortunately, we can figure it out knowing the current on the secondary side and the turns ratio.We now have the current and voltage present on the primary side. From here, we can get the power by multiplying them together.Here, the transformer needs to be rated for at least 540 kVA. -- source link

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