How to convert VA to Watts and KVA to Kilowatts Basics Since watts are volts time’s amps, what is VA? VA (or volt-amps) is also volts times amps, the concept however has been extended to AC power. For DC current VA = Watts (DC current). In AC if the volts and amps are in phase (for example a resistive load) then the equation is also VA=Watts (resistive load) where V is the RMS voltage and A the RMS amperage. In AC the volts and amps are not always in phase (meaning that the peak of the voltage curve is does not happen at the peak of the current curve). So in AC, if the volts and amps are not precisely in phase you have to calculate the watts by multiplying the volts times the amps at each moment in time and take the average over time. The ratio between the VA (i.e. rms volts time rms amps) and Watts is called the power factor PF. VA·PF = Watts (any load, including inductive loads) In other words, volt-amps x power factor = watts. Similarly, KVA*PF = KW, Or kilovolt-amps times power factor equals kilowatts. When you want to know how much the electricity is costing you, you use watts. When you are specifying equipment loads, fuses, and wiring sizes you use the VA, or the rms voltage and rms amperage. This is because VA considers the peak of both current and voltage, without taking into account if they happen at the same time or not Finding the Power Factor How do you find the power factor? This isn’t easy. For computer power supplies and other supplies that are power factor corrected the power factor is usually over 90%. For high power motors under heavy load the power factor can be as low as 35%. Industry standard rule-of-thumb is that you plan for a power factor of 60%, which somebody came up with as a kind of average power factor. Converting VA to Amps How to convert VA to amps? Use the following formula: Where A stands for the RMS amps, VA stands for volt-amps, V stands for RMS volts and PF stands for the power factor. Converting VA to Volts How to convert VA to volts? Use the following formula: Where V stands for RMS volts, A stands for the RMS amps, VA stands for volt-amps, and PF stands for the power factor. What is KVA? KVA is just kilovolt-amps, or volts time’s amps divided by 1000: KVA·PF = KW (any load, including inductive loads) Where KVA stands for kilovolt-amps, KW stands for kilowatts, and PF stands for the power factor. Keep the factor of 1000 straight when dealing with mixed units: KVA·PF = W/1000 (any load, including inductive loads) VA·PF = 1000·KW (Kilowatts to VA) The Following equations can be used to convert between amps, volts, and VA. To convert between kilovolt-amps, kilowatts, and kiloamps, keep track of the factor of 1000. Converting VA to Amps (voltage fixed) The conversion of VA to Amps is governed by the equation Amps = VA·PF/Volts) For example 12 VA·0.6/(12 volts) = 0.6 amp Converting KVA to KW (Kilovolt-amps to Kilowatts) The conversion of KVA to KW is governed by the equation KVA = Watts/PF) For example, if the power factor is 0.6 120 KVA·0.6 = 72 Kilowatts Converting Amps to VA (voltage fixed) The conversion of Amps to VA is governed by the equation VA = Amps · Volts/PF For example 1 amp * 110 volts/0.6 = 183 VA Converting Amps to KVA (voltage fixed) The conversion of Amps to KVA is governed by the equation KVA = Amps · Volts/(1000·PF) For example 100 amp * 110 volts/(1000*0.6) = 18.3 KVA Converting VA to Volts (current fixed) The conversion of VA to Volts is governed by the equation Volts = VA·PF/Amps For example 100 VA · 0.6/10 amps = 6 volts Converting Volts to VA (current fixed) The conversion of Volts to VA is governed by the equation VA = Amps · Volts/PF For example 1.5 amps * 12 volts/0.6 = 30 VA Converting Volts to Amps at fixed VA The conversion of Volts to Amps is governed by the equation Amps = VA·PF/Volts For example 120 VA* 0.6 /110 volts = 0.65 amps Converting Amps to Volts at fixed VA The conversion of Amps to Volts is governed by the equation Volts = VA·PF/Amps For Example, 48 VA · 0.6 / 12 Amps = 2.4 Volts Explanation Amps are how many electrons flow past a certain point per second. A volt is a measure of how much force that each electron is under. Think of water in a hose. A gallon a minute (think amps) just dribbles out if it is under low pressure (think voltage). But if you restrict the end of the hose, letting the pressure build up, the water can have more power (like watts), even though it is still only one gallon a minute. In fact the power can grow enormous as the pressure builds, to the point that a water knife can cut a sheet of glass. In the same manner as the voltage is increased a small amount of current can turn into a lot of watts.
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