I have heard that some guys have put a motor in the circuit just to deal with the harmonics as a filter to shore the sine wave up. An interesting idea, worth a try, but I bet it works on a case-by-case basis.
-- Will On Mon, Dec 21, 2015 at 10:12 PM, Jon Elson <el...@pico-systems.com> wrote: > On 12/21/2015 09:03 PM, William Donzelli wrote: >> >> If you can get a rotary one, those are really nice - just wasteful and >> loud. With proper maintenance they last forever, can take a beating, >> and do not give waveshape issues that cheap solid state units can >> have. And, maybe most importantly, you can make one yourself. >> >> But considering the mix of 50 and 60 Hz stuff you likely have by now >> (that is what you get for moving!), spending some decent money on a >> real VFD might be worth it. I might think a cheap VFD may give >> ferroresonant iron fits with all those extra harmonics. >> > You can't run electronics with VFDs designed to run motors, only. They put > out PWM chopped square waves at 300+ Volts. A motor's winding inductance > smooths that out to a proper current waveform, and it only causes a little > extra eddy current losses. But, typical transformers will have real fits > with that kind of waveform. > > There are "frequency changers" made by Elgar and others that will do the job > right, but they will cost a REAL bundle of cash! (Also known as frequency > converters.) > > It may be possible to retune the resonant circuit of the constant voltage > transformer by adding capacitance in parallel to the existing capacitor. > > Jon > >
