EE 212L: Power Factor Correction

Objective: The purpose of this lab is to use power factor correction (via a capacitor) to change a load's behavior such that it appears purely resistive, i.e., had a power factor of 1.

Pre-lab:

1. For the circuit shown in Figure 1 below, determine the following:
• impedance ZL of the load
• power factor angle of the load
• power factor of the load
• complex power absorbed by the load
• expected time shift between the load's voltage and current
2. Determine the value of a capacitor C that when placed in parallel with the original load impedance (see Figure 2) yields an equivalent power factor of 1. What is the value of this equivalent impedance? What relationship do we expect between the compensated load's voltage and current.

Laboratory Procedure: Recall that average power absorbed by a device or circuit is P = (1/2)VIcos(θ) W where V, I are the amplitudes of voltage and current, respectively, and θ = φV - φI is the phase difference between the element's sinusoidal voltage v(t) and current i(t). To obtain the most efficient use of the current delivered to a device or circuit, it is desired that the load voltage and current be in phase (θ = 0 and pf = 1).

• An inductor is a coil of wire and wire has resistance. Measure the resistance of your 0.47mH inductor. If this resistance is significant include it your calculations.
• Construct the following circuit.
• Experimentally determine the load's impedance ZL, power factor angle θ, power factor pf, and complex power using voltage and current measurements. Compare these to your predicted values found in the prelab.