vfd and my am radio addiction

oscer · Mar 9, 2011

Thanks to all who post on this forum. I was able to select and install a vfd on my bridgeport by reading on here. I thought I was good to go when I started it, changed speeds, reversed motor and then shut it off

But then I turned on the radio while it was running and it's all static :bawling:

So is this usual or did I miss something? I used a Teco jnev 101-h1. Input is 115 vac, output 230 vac 3phase. It's rated for 1HP the mill has a 1HP motor. I used shielded wire for the control circuit.

jim rozen · Mar 9, 2011

Me too. I typically tune in canada (CHWO) while working nights in the home shop.
VFD puts out enough hash (basically higher order fourier components in the PWM
waveform) to completely blanket out the signal coming in from external antenna.

My guess is that could be minimized by putting *all* the wiring between VFD and motor
into well shielded jacketing, AND putting the VFD in an all metal enclosure with an
RF gasketed cover, AND putting RF suppression at the power input, in the form of
feedthrough filters for power, and for the LF control lines.

oscer · Mar 9, 2011

Here are pics of the vfd. the arm is attached to the 5/8 -11tpi hole on top of the ram, it can be swiveled to the other side of the head if needed.

biometrics · Mar 9, 2011

Have you checked to see if this radio station streams its audio over the internet from their website... lots of stations do this. If you are receiving the audio through your PC (that you are using to presumably use this forum) there won't be ANY static... no matter what equipment you are running.

oughtsix · Mar 9, 2011

Dump the VFD and get a big Rotary phase converter. Mine is so loud I have never considered trying to listen to the radio while it is running!

Seriously though: The 3 phase power leads between the VFD and motor are big transmitting antennas. Shield... shield.. shield!!!

Try putting a ferrite core around the cable from the wall to the VFD... it might help some but I doubt you will ever be able to get a clean signal when the VFD is running.

oscer · Mar 9, 2011

Thanks for the help fellas, sounds expensive though, I think I'll just turn off the radio. I didn't want to put it in an enclosure because I wanted to use the pot. and the display. I would like to put one on my heavy 10 but between the two of them that will really cut into my easy listening.

HelicalCut · Mar 9, 2011

There is cable designed for use between the VFD and the motor, it is braid covered. I use it always because I found I was messing up the neighbours reception. Failing that anaconda or some other steel conduit might help. Read the VFD manual, most cover grounding and EMI in detail. Put a line filter on the feed as well.

fsmyth · Mar 10, 2011

Solution is simple:
Put the VFD and controls in a metal enclosure, and
use flexible metal conduit in and out. I started
running into this problem with all the plastic VFD
housings (mostly interference with wireless ethernet).
I use liquid-tight conduit - it is easier to keep clean.
In extreme cases, we have had to add RF chokes to
the output lines. Usually this is because the motor
itself is not completely enclosed. Ground EVERYTHING.
<als>

DaveKamp · Mar 10, 2011

And...

Another way, is to check your AM receiver for external antenna connections... if so, use those connections to go to an outside antenna.

Improving signal to noise ratio... is mainly about reducing noise, but increasing signal is a very effective method of offsetting that ratio, too.

oscer · Mar 10, 2011

I'll try some of this avise when I get the mill back together. I started taking it apart to paint it. Someone painted part of it a nasty looking tan. Might not have bothered me so much if it was all the same color but now's the time to paint it because it's going to take me a while to buy tooling for it. I won't be chomping at the bit so bad to start running it if it's all tore apart.

mrvinton · Mar 10, 2011

Try this convert your AM to FM. Works great where you cant get AM inside of a building. VFD could still be a problem

C. Crane Company - Digital FM Transmitter - Toll Free (800) 522-8863

Marcibb · Mar 11, 2011

I added a home made FR Choke to the input line of my FM50 it took care of the problem entirely. I will take a picture or two and post them later.

Marci

My daughter has my camera but here is the schematic

The only parts that may not be readily available off the shelf are the inductor L1,2,3 but you can make them your self using insulated size 14 wire (you can get this from any motor repair shop get the high copper content stuff it bends much easier) and a toroid loop

this one is available for about $1.50 from mpja wind as many turns as you can

Hope this helps

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