Re: [CAD_CAM_EDM_DRO] RF problem with VFD help

OK I have tried the smaller capacitors as I had drawn and the 1uf and it did not seem to make any difference. I next changed the carrier frequency setting from 4 (10kzh) down to 1 which is aprox
2.5khz. This carrier freq reduction helpped by aprox 60 or so reduction in RFI. Is there anything else that I can do to reduce this more?

Thanks
Stan


Jon Elson wrote:

> stan mcdonald wrote:
>
> > Hello list.
> > I have an inverter 220 single phase 40 amps draw at full load, it
> > generates alot of RF noise on the AM radios.
> >
> > To eliminate this noise problem seems to be more of a challange then I
> > had hoped for but I have to eliminate this. I have installed a 1" pipe
> > in the ground about four feet down and then removed a screw from the
> > condute inspection cover from the hydro meter and ran a wire from the
> > meter cover down to this grounding rod. This helps some. I also grounded
> > the machine to the breaker box since it is about 20 feet from the box I
> > took the liberty of using alot heavier wire then is required. I also
> > installed the inverter in a steel NEMA box. I have two options that I
> > know of left. Build a filter or use an isolation transformer.
> >
> > The transformer is expensive so I looked through some electronics books
> > and found a low pass filter which is suposed to pass 60 HZ
> >
> > 220 single phase in __________L1_____I___________ SINGLE PHASE OUT
> > I
> > I
> > C1
> > I
> > I
> > 220 single phase in __________L2______I____________SINGLE PHASE OUT
> >
> > C1=0.01 UF
> > L1 & L2 1MH
> >
> > The capacitor is no problem but where can I get a coil that will pass
> > the 40 amps?
> > Is there a better way to eliminate this RF?
>
> You can make your own inductors. You may not need a lot of inductance.
> If you can find some ferrite material, just winding insulated wire around
> it makes an inductor. Even without the ferrite core, just winding wire into
> a coil provides inductance, just not as much. Also, what you want is to
> put the capacitors (need to be rated for line to ground service) from line
> to ground. .01 uF is pretty small. You may need as much as .1 uF of
> capacitance, and may need to use 4 of them, 2 before the inductors, and
> 2 after.
>
> I had the same problem (drove my computer controlled air compressor
> wild, and also put fuzz on the video monitor on my CNC machine) but I
> was only running 1 Hp on the mill, so I used a modest commercial line filter
> unit. I have seen some of these in larger sizes in such catalogs as
> C&H, Herbach&Rademan, Surplus Center, etc.
>
> Jon
>
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