Now, if you look at the “1,000 ÷ 1.732V” portion of this equation, you can see that by inserting the respective 3-phase voltage for “V” and multiplying it by 1.732, you can then divide that resulting quantity into “1,000” to get a specific number (or constant) you can use to multiply “kW” to get the current draw of that 3-phase load at the respective 3-phase voltage. We Deliver.Lower Cost, Quality Products, and Personal Service. From this we can derive the following equations: Active power. Formulas for calculating motor amps, horsepower(hp), kilowatts(kW) and kVA for DC, single phase AC, and 3 phase AC motors- Elliott Electric Supply wholesale electrical supplies. If you have a piece of equipment that draws 80A, then you can calculate the relative size of the required power source, which is 10kW (80 ÷ 8.33).īy using this same procedure but inserting the respective single-phase voltage, you get the following single-phase constants, as shown in Table 1.įor 3-phase systems, we use the following equation:Īgain, assuming unity PF and solving this equation for “I,” you get: One of the consequences of using the power triangle is that we can easily establish the mathematical relationship between the three values with the use of the Pythagorean theorem: S² P² + Q². So, if you have a 10kW load, you can calculate the current draw to be 83.3A (10 × 8.33). Wire Circular Mils (Conductor Resistivity) (2) (Amps) (One Way Distance in Feet) Allowable Voltage Drop For 3-phase circuits: Wire Circular Mils (Conductor Resistivity) (2) (Amps) (One Way Distance in Feet) (. Now, if we look at the “1,000 ÷ V” portion of this equation, you can see that by inserting the respective single-phase voltage for “V” and dividing it into the “1,000,” you get a specific number (or constant) you can use to multiply “kW” to get the current draw of that load at the respective voltage.įor example, the constant for the 120V calculation is 8.33 (1,000 ÷ 120). Single-Phase Calculationsīasic electrical theory tells us that for a single-phase system,įor the sake of simplicity, let's assume the power factor (PF) is unity. You can use constants that apply to specific single- and 3-phase voltages to calculate current (I) and kilowatts (kW). No matter what the circumference and diameter of the respective circle, their ratio is always pi. You may ask, “What exactly is a constant?” An example of a constant with which you're very much familiar is pi (π), which is derived by dividing a circle's circumference by its diameter. We'll also show you how you can do these calculations “in your head,” with very reasonable accuracy, through the use of constants. This month, we'll discuss the most fundamental of calculations - those for current (I) and kilowatts (kW).
2 PHASE POWER CALCULATOR ONLINE SERIES
Welcome to the first in a series of articles focusing on electrical calculation basics. right UPS to protect your servers, switches, routers and networking devices in distributed IT and edge environment (single phase power up to 20 kVA).
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