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Electrical noise from drives and welders

Drives and welders are easy to blame for Wi-Fi drops, but most drive noise sits far below the Wi-Fi bands, so prove it with a spectrum capture and a timing match before you act on it.

Ben RutterIndustrial network engineer
  • Updated
  • Reviewed
  • 2 min read
  • 5 sources
On this page5 sections
  1. How it presents
  2. Why it happens
  3. How to confirm it
  4. The fix
  5. Prevent it at design time

Is this your problem? It presents like this

  • Drops cluster near specific machinery, such as drive cabinets, welding cells, or large motors.
  • They follow that machine's duty cycle rather than time of day or traffic load.
  • Short flickers are more common than long outages.
  • A fixed device mounted on or beside the machine suffers most.
  • The noise floor reported by the access point or client rises when the machine runs.
Not sure?
Rank the likely causes from your symptoms

Why it happens

Most drive and motor noise lives far below Wi-Fi. A drive’s fast switching produces conducted interference in the 150 kHz to 30 MHz1 range and radiated interference from 30 MHz to 1 GHz. NIST notes that noise from rotating motors typically affects bands below 400 MHz2. The Wi-Fi bands on a typical plant floor start at 2.4 GHz.

Arcs are the exception worth testing. NIST separates low-frequency noise from motors and solenoids from higher-frequency noise from arc-generating equipment. A trade article on industrial WLANs warns that brushed motors arc and spark like a spark-gap transmitter, and that drives can disrupt wired and wireless links when they are poorly located and wired. Welding cells and brushed motors deserve a measurement, not a verdict.

The evidence is a match in both time and frequency. NIST recommends spectrum monitoring that can correlate spectral activity to factory activities, and one industrial Wi-Fi guide says it directly: do not blame every electric motor near a null. Misattribution runs both ways, too. A drive supplier quoted in the trade press notes that arc welding can trip drives while the drive takes the blame. If the Wi-Fi channel looks the same with the machine on and off, the machine is not your problem.

How to confirm it

  1. Log the machine's run, weld, or drive state with timestamps from its controller or the production log.
  2. Line those timestamps up with client drops, retries, and noise floor readings. A match across many cycles is evidence; one coincidence is not.
  3. Record a spectrogram at the affected device, on the Wi-Fi channel in use, with the machine running and then stopped.
  4. Look for broadband energy inside the Wi-Fi channel that starts and stops with the machine. If the Wi-Fi channel looks the same either way, the machine is not your RF problem.
  5. If production allows, start and stop the machine on purpose and watch the link.
  6. Check the device's power supply and cabling. Noise that enters through a shared supply or an unshielded cable is a wiring fault, not an RF one.
  7. If the spectrum stays clean, move on to the other causes in this library before you touch the machine.

The fix

  • If the spectrum confirms it, add distance or a metal barrier between the antenna and the source, or move the antenna.
  • Fix the installation with shielded motor cable, proper grounding and bonding, separated power and signal runs, and filters as the drive supplier specifies.
  • Move the client to a band the measured noise does not reach.

Prevent it at design time

  • Keep access point and client antennas away from drive cabinets, motor leads, and welding cells.
  • Follow the drive supplier's EMC installation guidance for cabling and filtering.
  • Record a baseline spectrogram with the machines running during the site survey.

Related causes

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About this page

Built from 5 sources: 2 standards bodies and labs and 3 other sources. Researched and drafted with AI assistance, then reviewed and approved by Ben Rutter on . How pages are made

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Cite this page

Plain

Ben Rutter. "Electrical noise from drives and welders." OT Wireless, published October 5, 2026. https://otwireless.com/causes/electrical-noise-from-drives-and-welders/

APA 7

Rutter, B. (2026, October 5). Electrical noise from drives and welders. OT Wireless. https://otwireless.com/causes/electrical-noise-from-drives-and-welders/

BibTeX

@misc{rutter2026electricalnoisefromdrivesandwelders,
  author = {Rutter, Ben},
  title = {{Electrical noise from drives and welders}},
  year = {2026},
  howpublished = {\url{https://otwireless.com/causes/electrical-noise-from-drives-and-welders/}},
  organization = {OT Wireless},
}