NEMA 1 VFD filter

K

Ken H>

Joined
Dec 31, 2011
Messages
4,560
Hello all, I've been using the cheap Chinese VFDs for a few yr now with success. The trick is to either put in a dustproof enclosure, or adequate inlet filters to prevent metal dust from getting inside to the electronics. Here is the way I've attached filters - use the adhesive backed velcro to hold filter in place. A couple of photos makes it easy to see.
The first shows how the velcro is glued around the air inlets. The air movement on these VFDs seem to always be with the fan pulling air in thru all the other openings and out at the fan.

VFD-Filter-Velcro.jpg


The next shows the filter material attached to the velcro. The velcro makes it easy to remove, clean, and install again with the fan not covered so it can exhaust air freely.
VFD-Filter.jpg
 
That’s pretty slick. What is the filter material you used? Is there anything specific that is better/worse?

Jeremy
 
You should stick a few magnets underneath that filter. You maybe surprised how much ferrous shmoo gets past.
 
That's a good idea - think I'll try it and see how goes thru the filters. Darn good idea in fact.
 
Ken, this may be the first post with a photo I've ever seen from you ;)

I did something similar for the air compressor my pops gave me as a gift in my first shop. Worked well, still runs anyways!

-Clint
 
So much for that idea. No idea where I can come up with that kind of $ for those filters.... ;). Thanks for the link.

Jeremy
 
I just bought the same vfd. I had planned to make a box but kind of want to keep it simple and accessible. I think if i mount the vfd away from the grinder and use filters it should be good. If not, $75 isnt all that expensive if it runs for many years.
 
Randy, I mount my VFD drives right there on the grinder, just behind the motor so I can easy see the display. I've programmed the display to show the SFPM belt speed rather than RPM or freq. I've wired a pot and switches in a box to control the VFD. Using the buttons on the VFD just not as convenient.

I like the idea of mounting a magnet inside the VFD cover to attract any stray metal dust that gets thru the inlet filters.
 
Ken,

At wally world i found seversl filters like what you linked. I noticed some were tighter woven then others. I got the tightest ones. I was curious if you did the magnet thing and whaat your results were.
 
Yes, I did do the magnet thing, and found out the magnet doesn't work so well with the electronics of the VFD. I mounted magnet on outside of case (under filter), but the VFD didn't run correctly then. At slow speed it was ok, but when cranked up to 80% to 100% the motor didn't turn as fast as it should, no power, and after a couple of minutes there was smoke coming from inside case where something was getting hot. I quickly turned off, removed magnet - now it runs just fine.

I think the magnet flux affected something inside - I just figured that out yesterday and planned to post my experience today, but the Iron Bowl got in the way (grinning).

I'll just depend on the filter to keep metal dust out. It's been working ok for the last 3 or 4 yrs on the grinder. Just this summer I built the horizontal grinder and disk grinder - added filters to both of those.

I expect the filter material you've got will work just fine.

Ken H>
 
Roll Tide!

Good to know about the magnets and vfd not getting along. Sucks you had to find out that way. Glad i asked!

Moving magnets can induce electrical currents in a closed loop. I am not sure what could cause a stationary magnet to affect a vfd, but i do know there is a lot of complicated stuff happening inside those things.
 
Does this thing have an off switch? I have just been been unplugging it.

Just checked the vfd manual and it says no electromagnetic interference

bctWt1o.jpg
 
I guess they mean it when they say "no electromagnetic interference" {grinning}

Nope, there's not OFF/ON power switch, I always mount a DPST switch to open the power circuit. I mount in same box as the FORWARD/OFF/REVERSE switch which is a SPDT 3 position switch. Depending on which VFD I've got, I'll either mount a 10K pot in the cover of VFD (or in box) for easy speed adjust.
 
I built a box for my TECO as it was also unenclosed. The problem I had with using filters as you did was where the wires all attached. That is right by the intake opening on the bottom of the VFD. I could not see how to isolate that with velcrod (sic) filters. How did you protect that junction?
 
It's by no means sealed around the wires coming in - I just formed some filter material over 'n around the wires coming in and let it go. The filter material provides sort of a "air dam" in front hoping that will prevent metal dust from entering. My thinking it's only a $70 VFD and if it does go bad in a yr or so, not a lot lost and I'll do a better job then. I didn't wish to put my VFD inside a box because I wanted to see the display easy to see the belt speed. I've got the display set to show the SFPM belt speed rather than rpm or freq.
 
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