Why do an inverter or a welding machine affect electronics?
An inverter and a welding machine switch current very fast; the resulting high di/dt produces broadband noise both conducted along the cables and radiated through the air. The welding current returning over the chassis also shifts the chassis potential. The measures are: connecting the welding earth clamp as close as possible to the working point and disconnecting sensitive devices from the circuit while welding.
There are two separate mechanisms. The first is switching noise: at the inverter output the voltage changes with a large jump in less than a microsecond (high di/dt and dv/dt); this fast change both rides on the supply lines and radiates from the cables. The second is specific to welding machines: a welding current of hundreds of amps returns through metal from the workpiece to the earth clamp and shifts the chassis potential along the path it takes. If the electronics enclosure sits on that path, its reference slides out from under it.
Practical measures:
- Connect the welding earth clamp right next to the point you are welding; do not let the current return through the vehicle wiring or the control enclosure.
- Before welding on the vehicle, disconnect the battery terminals and the connectors of sensitive control units.
- Keep the inverter supply cables short and twisted, and separate them from signal cables by at least 15 cm.
- Add a common-mode choke and a suitable X/Y capacitor combination at the inverter input.
- On screened signal cables, connect the shield to chassis at one end only, with 360-degree contact; do not use a pigtail.
Switched-mode welding also creates voltage fluctuation on the vehicle supply; the supply protection components must be chosen to suit these conditions.
The full topic: Installation, redundancy and field continuity