Published December 18, 2025 · by Tyler Wray
Variable frequency drives on agricultural pumps are one of the easier wins for energy efficiency on a Central Valley parcel. They are also one of the easier ways to create a power-quality problem you didn't know you had — until PG&E shows up with a meter.
Why ag pumps are different
A 200 HP deep-well pump runs near-continuous duty during irrigation season. The drive's input current is rich in 5th, 7th, 11th and 13th harmonics. On a residential or light-commercial distribution branch, those harmonics distort the voltage waveform for everyone fed from the same transformer.
What we specify
- A line reactor sized to the drive at minimum — not optional.
- An 18-pulse drive or an active front end on anything above 100 HP fed from a shared transformer.
- A passive harmonic filter when 18-pulse hardware is impractical.
- An actual measurement, not an assumption, before and after commissioning.
What gets skipped
All of the above, frequently. The drive ships, the installer wires it up, the pump runs, and nobody measures total harmonic distortion until the irrigation district or the utility calls. Build the filter and the measurement into the original quote — it is cheaper than the retrofit.