In the last month, I have been contacted by two women driven out of their homes by illness caused by neighborhood installation of water pumps with variable frequency drives (VFD) or variable speed drives (VSD) or controllers. These are solid state devices which replace mechanical motor switches to controlmotor speed and torque by varying motor input frequency and voltage. One was a solar powered water pump using a maximum power point tracking (MPPT) controller to maximize charging of batteries which powered a water pump motor. The other was a VFD on a replacement deep well pump motor. When this pump was running, dirty electricity levels in the house spiked as did the primary neutral to earth voltage dumped into the earth at a transformer near the house. These devices all interrupt current flow and generate high levels of high frequency voltage transients or dirty electricity. The industry calls this radiated noise or common mode noise. See: http://www.belden.com/docs/
Dairy farmers were the first to recognize the problem, since installation of VFDs on milk pump motors caused an immediate drop in milk production. A 10 millivolt change in dirty electricity in the milking parlor floor equals a change of about a pound of milk per day in each cow.
Sci Total Environ. 2013 Mar 1;447:500-14. doi: 10.1016/j.scitotenv.2012.12.
VFDs are also being put on the motors of many new air conditioners and furnace fans.
The inverters and controllers on residential and commercial photovoltaic solar systems and wind turbines all generate dirty electricity.
Best, Sam Milham