Finding sum of phasors when real components cancel out

In summary, the problem involves adding two phasors together and determining the phase when the real parts cancel out. The solution involves converting the phasors to rectangular form, adding them together, and then finding the magnitude and phase of the resulting vector. In this case, the resulting vector is purely imaginary and therefore the phase is 90°.
  • #1
CE Trainee
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0

Homework Statement



I'm working on a problem where I have to add two phasors together. The problem is, the real parts cancel out and I can't figure out how to express the phase because arctan(y / 0) isn't defined.

Homework Equations



x1 = 10<45 degrees

x2 = 10<135 degrees

x1 + x2 = ?


The Attempt at a Solution



x1 in rectangular form = 7.07 + j7.07

x2 in rectangular form = -7.07 + j7.07

x3 = x1 + x2 = 0 + j14.14

x3 magnitude = 14.14

x3 phase = arctan( 14.14 / 0 )?
 
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  • #2
CE Trainee said:

The Attempt at a Solution



x1 in rectangular form = 7.07 + j7.07

x2 in rectangular form = -7.07 + j7.07

x3 = x1 + x2 = 0 + j14.14

x3 magnitude = 14.14

x3 phase = arctan( 14.14 / 0 )?


if x3=14.14j, then it is purely imaginary and thus the vector is parallel to the imaginary plane. So the angle it makes with the real plane is just 90°.
 

1. What is a phasor?

A phasor is a complex number used to represent a sinusoidal function in the frequency domain. It has a magnitude and a phase angle, which represent the amplitude and phase of the sinusoid, respectively.

2. Why do the real components cancel out in some cases?

In some circuits or systems, there may be equal and opposite real components that cancel out each other. For example, in an RLC circuit, the reactive components (inductance and capacitance) can cancel out the resistance, resulting in a purely imaginary impedance.

3. How do you find the sum of phasors when the real components cancel out?

To find the sum of phasors when the real components cancel out, you can use the Pythagorean theorem. First, square the magnitudes of the phasors, then add them together. Finally, take the square root of the sum to find the magnitude of the resulting phasor. The phase angle of the resulting phasor can be found using trigonometric functions.

4. What is the significance of finding the sum of phasors with canceled real components?

Finding the sum of phasors can help in analyzing and solving complex circuits or systems. When the real components cancel out, it means that the system has a purely reactive impedance, which can affect the behavior of the system. By finding the sum of phasors, we can determine the overall impedance and phase angle of the system.

5. Can the sum of phasors with canceled real components be a negative value?

No, the sum of phasors will always result in a positive magnitude, as it is the square root of the sum of squared magnitudes. However, the phase angle of the resulting phasor can be positive or negative, depending on the direction of the phasors in the complex plane.

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