Calculate the phase angle of a circuit using some basic trigonometry. Use the power triangle, which is based on the measurements of true power, reactive power and apparent power. True power is measured in watts and symbolized by the letter P. Reactive power is measured in volts-amps-reactive and symbolized by the letter Q. Apparent power is measured in volts-amps and symbolized by the letter S. The adjacent leg of the triangle is formed by P, the opposite leg is formed by Q and the hypotenuse is formed by S. The phase angle, then, is the angle between S and P.
Instructions
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1
Find Q by multiplying amperage squared by the reactive voltage of the circuit. For example, in a circuit with 5 amps and a resistance under load of 60 Ohms the reactive power is 1500.
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2
Find P by multiplying volts by amps, so a 5-amp circuit running at 120 volts yields 600 W of power.
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3
Use the trigonometry formula for a tangent to find the phase angle. So divide P by Q, which in our example gives us 600 divided by 1500 for a quotient of 0.4.
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4
Isolate for the angle by taking the inverse tangent of the quotient which gives a phase angle of 0.38 degrees for our example.