I have a cnc router in my shop that has a VFD (variable frequency drive) I have been running it for ten years. when I first got it I had snow on the monitors when it was running. that went away with the use of hdmi cables. or the monitors changed who knows? but around the iPhone 5 or 5s not sure when I tried charging my phone when the machine was running I could not use it because the touch screen was so glitchy. I did not have to charge often because they did not have pokemon go back then (G) so since then I charge with a battery. it has gotten a little better with each new phone. it is there only a little on the 8 but it can still make it less then accurate trying to use the phone while charging. what disappointed me is it is the same with the mophie wireless charger too. Now I have had people charge their android phones in m,y shop and it does not effect their phones. The VFD is on a 3 phase line but it effects both of my 110 lines. . my power comes from another main box that other people use but it does not reach their outlets.