![]() ![]() Power triangle relating apparent power to true power and reactive power. We call this the power triangle: (Figure below). These three types of power-true, reactive, and apparent-relate to one another in trigonometric form. True power, reactive power, and apparent power for a resistive/reactive load. True power, reactive power, and apparent power for a purely reactive load. True power, reactive power, and apparent power for a purely resistive load. There are three equations available for the calculation of apparent power, P=IE being useful only for that purpose.Įxamine the following circuits and see how these three types of power interrelate for: a purely resistive load, a purely reactive load, and a resistive/reactive load. Please note that there are two equations each for the calculation of true and reactive power. There are several power equations relating the three types of power to resistance, reactance, and impedance (all using scalar quantities): If I’m calculating apparent power from voltage and impedance, both of these formerly complex quantities must be reduced to their polar magnitudes for the scalar arithmetic. Since we’re dealing with scalar quantities for power calculation, any complex starting quantities such as voltage, current, and impedance must be represented by their polar magnitudes, not by real or imaginary rectangular components.įor instance, if I’m calculating true power from current and resistance, I must use the polar magnitude for current, and not merely the “real” or “imaginary” portion of the current. Reactive power is a function of a circuit’s reactance (X).Īpparent power is a function of a circuit’s total impedance (Z). Calculating for Reactive, True, or Apparent PowerĪs a rule, true power is a function of a circuit’s dissipative elements, usually resistances (R). The combination of reactive power and true power is called apparent power, and it is the product of a circuit’s voltage and current, without reference to phase angle.Īpparent power is measured in the unit of Volt-Amps (VA) and is symbolized by the capital letter S. The actual amount of power being used, or dissipated, in a circuit is called true power, and it is measured in watts (symbolized by the capital letter P, as always). The mathematical symbol for reactive power is (unfortunately) the capital letter Q. ![]() This “phantom power” is called reactive power, and it is measured in a unit called Volt-Amps-Reactive (VAR), rather than watts. So amps are equal to 1000 times kilovolt-amps divided by 3 times volts.We know that reactive loads such as inductors and capacitors dissipate zero power, yet the fact that they drop voltage and draw current gives the deceptive impression that they actually do dissipate power. The line to line RMS voltage supply is 190 volts?ģ times the line to line RMS voltage V in volts: Question: What is the phase current in amps when the apparent power is 3 kVA and So amps are equal to 1000 times kilovolt-amps divided by the The square root of 3 times the line to line RMS voltage V in volts: The phase current I in amps is equal to 1000 times the apparent power I = 1000 × 3kVA / 110V = 27.27A 3 phase kVA to amps calculation formula Calculation with line to line voltage Question: What is the phase current in amps when the apparent power is 3 kVA and the RMS voltage supply is 110 volts? So amps are equal to 1000 times kilovolt-amps divided by volts. The phase current I in amps is equal to 1000 times the apparent power S in kilovolt-amps, divided by Single phase kVA to amps calculation formula Volts, but you can't convert kilovolt-amps to amps since kilovolt-amps and amps units do not measure the same quantity. You can calculate amps from kilovolt-amps and How to convert apparent power in kilovolt-amps (kVA) to electric ![]()
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