![]() No further rounding or conversion is needed, since 30 KVA is a standard three-phase transformer size. Taking our final three-phase figure of 30 KVA, we can see that it matches with a standard three-phase transformer size above, i.e., 30 KVA. As a solution, simply round up to the next standard single-phase KVA size: 7.5 KVA. Taking our answer from the single-phase example above – 6 KVA or 7.2 KVA (with 20% spare capacity) we can see that there is no standard single-phase equivalent available. If you cannot find the size you need, simply round up again to the next standard KVA size.įor referencing, the standard KVA sizes for singe-phase transformers are 1, 1.5, 2, 3, 5, 7.5, 10, 15, 25, 37.5, 50, 75, 100, 167, 200, 250 and 333 KVA. In most cases, this is because there are standard KVA sizes for transformers. Engineering ToolBox - SketchUp Extension - Online 3D modeling 3D. Lastly, one may find that the specific transformer size needed is not being offered or is unavailable by the store or preferred manufacturer. Inductive loads and power factors with electrical three-phase motors. s AC Power Calculator is an online electrical engineering tool to calculate the power consumed by the load connected in single phase, three phase or two phase four wired transmission lines or circuits. Taking the three-phase sample again, we simply add 20 percent to the rounded figure: Next, in order to factor in future expansion and prevent risks associated with accidental overloading, one should add 20 percent of spare capacity. It is best practice to always round up and not down. As a result, the value must be rounded up, as seen in the sample above. Most computations (especially for three-phase loads) do not provide a whole number. = 24.94 KVA (or 25 KVA after rounding up) Future Expansion and Standard Transformer SizesĬomputing for the required KVA is not the final step in determining the proper transformer size. With this in mind, the new formula can be found below:Įxample: Find the KVA or transformer size for load voltage of 240 3PH and a load current of 60 amps. ![]() ![]() Furthermore, three-phase transformers handle three lines of AC power, with each of the three lines 120 degrees out of phase from the other two lines. This figure is a constant found in three phase, as the phases do not generate the same amount of power (simultaneously). Note that load voltage is not the same as line voltage, which is also known as primary voltage or input.Įxample: Find the KVA or transformer size for load voltage of 120V 1PH and a load current of 50A.īusinesses that require three-phase power need to add an extra component in the formula to arrive at the correct transformer size, i.e., square root of 3 (√3) or 1.732. The formula for finding the required KVA or transformer size for single-phase power is the following:īased on the equation, one would need to plug in the proper load/output (secondary) voltage and current (amps) to compute for KVA.
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