Okay, let's break down what you're seeing and try to interpret the readings from your line reactor installation on your well VFD. You're trying to reduce harmonic distortion from the VFD, primarily to avoid issues with your AFCI breakers.

Understanding Line Reactors & VFDs VFDs and Harmonics

VFDs (Variable Frequency Drives) are great for controlling motor speed efficiently, but their internal switching creates harmonic currents and voltages. These harmonics are multiples of the fundamental frequency (60 Hz in the US). They can cause problems like: Overheating in transformers and wiring. Nuisance tripping of circuit breakers (especially AFCIs and GFCIs). Interference with sensitive electronic equipment.

Line Reactors

Line reactors (also called chokes) are inductors placed in series with the AC line feeding a VFD. Their purpose is to: Reduce the magnitude of harmonic currents being drawn by the VFD. Reduce the rate of rise (dv/dt) of voltage transients caused by the VFD switching. Improve the power factor of the VFD system (though this is typically a secondary benefit).

Interpreting Your Measurements1. Voltage and Current Sine Waves at Panel

The fact that you don't see a dramatic difference in the voltage and current sine waves at the main panel after installing the line reactor is not entirely unexpected, especially with just a visual inspection on your Fluke 43B. The level of distortion could be relatively low to begin with (the VFD could be small or the system impedance is low). Harmonic currents often represent a small percentage of the total current. A more detailed harmonic analysis with the Fluke 43B (or a dedicated harmonic analyzer) before and after would give you quantitative data to see the reduction in the harmonic content. You want to look specifically at THD (Total Harmonic Distortion) and the individual harmonic magnitudes (3rd, 5th, 7th, etc.).2.

Frequency Measurements (Fluke 87)



A1 to A2 (Line Side) = 60 Hz

This is exactly what you expect. The incoming line frequency should be a clean 60 Hz.

C1 to C2 (Load Side) = 120 Hz

This is very likely a result of the VFD's internal switching. VFDs rectify the AC input to DC and then use a PWM (Pulse Width Modulation) inverter to recreate a variable-frequency AC output for the motor. This PWM creates a complex waveform with a strong 2nd harmonic (120 Hz). It indicates the line reactor is not able to remove all of the generated harmonics.

C1/C2 to EG (Equipment Ground) = 2.56 kHz

This is the most interesting and concerning measurement. This higher frequency component suggests high-frequency noise or ringing on the output of the VFD, likely due to the PWM switching frequency and the impedance of the motor cable. The line reactor is likely filtering some of this. This noise is a major cause of problems with AFCIs and can also cause radio frequency interference (RFI).

What You Can Conclude & What You Should Do The Line Reactor is likely having some effect

The presence of the 120 Hz and 2.56 kHz components on the load side (VFD input side) of the reactor, and their relative absence on the line side, suggests the reactor is attenuating some of the high-frequency noise generated by the VFD.

The Reactor May Not Be Enough (Alone)

The 2.56 kHz component to ground is still present. This is a significant indicator that the reactor, by itself, might not completely solve your AFCI tripping issues.

Meaningless? The measurements are not meaningless if it leads to further investigation. However, frequency readings aren't as conclusive as harmonic analysis.

Recommendations


Harmonic Analysis

Use your Fluke 43B to do a proper harmonic analysis before and after the line reactor. Measure Total Harmonic Distortion (THD) and individual harmonic magnitudes (3rd, 5th, 7th, etc.) on both the line side (A1/A2) and load side (C1/C2) of the reactor. This will give you concrete numbers to quantify the reactor's performance.2.

Motor Cable

The type and length of motor cable running from the VFD to the well pump motor are critical. Use a shielded cable specifically designed for VFD applications (e.g., VFD cable or a cable meeting UL 1277 and CSA 22.2 No. 239 standards). Make sure the shield is properly grounded at both ends (VFD enclosure and motor enclosure). Long cable runs greatly increase the capacitive coupling between the VFD output and ground, creating a path for high-frequency noise.3.

Load Reactor

Consider adding a load reactor (also called a motor choke) at the VFD output terminals and near the VFD. This will provide additional filtering to reduce the voltage distortion and dV/dt at the motor terminals, further reducing the high-frequency noise being radiated.4.

AFCI Breaker Type

Some older AFCI breakers are more prone to nuisance tripping than newer models. If possible, try using a newer "dual-function" AFCI breaker that is less sensitive to harmonic currents. (Check compatibility with local codes!)5.

Grounding

Ensure proper grounding throughout the system, especially at the VFD, motor, and main electrical panel. A solid, low-impedance ground path is essential for diverting high-frequency noise. Use a star grounding configuration if possible.6.

Check VFD Settings

Some VFDs have adjustable PWM switching frequencies. Lowering the switching frequency can reduce harmonic noise (but might also slightly decrease motor performance). Consult your VFD manual for instructions.7.

Ferrite Bead

Clip-on ferrite beads on the conductors.

Regarding Your AFCI

The fact that your AFCI breaker "threw sparks and failed" during a test is not normal and indicates a serious problem. Replace the breaker immediately! Do not try to reuse it. And double-check the wiring to that circuit.

In summary: You've taken some initial steps. Continue with the harmonic analysis to get quantitative data. Pay close attention to the motor cable, grounding, and consider a load reactor. And most importantly, replace that failed AFCI breaker before something bad happens! Flag for review