VFD Placement

An induction motor is totally contactless (at least a 3-phase one is) and contains no rectifying elements: it'll be about as RF free as anything could be on an AC line. If the VFD generates RF and lets it loose on the motor lines then the motor'll radiate -- but only because of the VFD, not as a fault of the motor.

Greetings Wayne, VFDs work by switching on and off rapidly. This creates lots of RF noise. Two machines in my shop have big DC spindles drives. These rectify (ie change AC to DC) the 230 3 phase input and chop up the output to change the speed of the spindle. So they are similar in operation to VFDs. They are really noisy in the AM band. Placed any closer than about 20 feet an AM radio put out a really annoying squeal.If mounting in a VFD encloser you will need to be sure it will get enough cooling. The VFD I have says somewhere in the manual that it needs a certain amount of cooling and there is a way to figure out how much air flow is needed to achieve a certain amount of cooling based on ambient air temp. Can you place some kind of shield in front of it? I'm picturing a piece of sheet metal 6 inches wider and several inches longer. Then it could be bent at an angle and screwed to the wall such that it covers the top, bottom and front while leaving the sides open. There would be a few inches clearance between the front, top, and bottom of the VFD and the piece of sheet metal. The sheet metal would be bent so that when attached to the wall it slopes at the top so any chips that fall on it will slide off. BTW, there is no 3 phase to my shop so I make it with a rotary phase converter (RPC) Three machines in the shop need good 60 hertz 3 phase input to make the servo drives and/or spindle drives work. But all the smaller machines are 1 HP or less and don't have CNC controls. Since the big RPC draws about 1500 watts just idling I'm going to start putting VFDs on the smaller machines and only turn on the RPC when it's needed. I think they are a great invention and wish they were cheaper when I was first wiring the shop 8 years ago. Cheers, Eric

Chips getting into it are a much bigger issue than oil, which is mostly a cosmetic thing, unless by "oil" you mean a water based coolant.

The enclosure won't help much with electrical noise. The biggest problem is noise introduced back into the power line. A line inductor will usually help if this proves to be a problem, but unless you have something very sensitive in the area, or an AM radio, you shouldn't be troubled by noise.

I've got the VFDs on both my lathe and mill mounted out in the open for just this reason.

On the lathe the VFD is on a stanchion, on the mill, obscured by the chain hoist in the photo, the VFD is on the top side of the DRO arm.

Ned Simmons

Your lathe is a great looking machine. What brand and model is it?

Is the motor on the carriage for power cross feed?

WB .................

And some VFDs generate considerable amounts of RFI..I as a service technician can sometimes find new customers by listening to my AM radio in the truck and driving through industrial strips until I get to the maximum noise. Shrug.. They dont seem to bother TV, FM etc..but AM radio is pretty common. And Ive seen some older units put interference into Ethernet networks, though its very very rare.

The manufactures are getting better at making quieter devices. Btw...shielding them in an enclosure seldom helps, as it radiates via the motor wiring.

Gunner

Every normal man must be tempted, at times, to spit on his hands, hoist the black flag, and begin slitting throats. H. L. Mencken

It's the English-only version of this lathe...

There are a couple other Taiwanese makers of similar copies. Victor is one and there's another whose name I can't remember. MSC sells one under their Vectrax name, Wilton also sells a rebadged version. There's also Ganesh, which, based on the name, I was afraid might be an Indian clone, but appears to be Taiwanese as well.

Ned Simmons

Thanks all for the replies.

The verdict is the VFD stays in the open. It is under a cabinet (with breathing room). I'll add a board or piece of plexiglass on the right side of the VFD and up to the cabinet. That should keep it clear enough from anything the lathe wants to toss around.

The only RF noise I heard was AM also. That antenna is in the basement, not far from the lathe. All the other antennas are on the roof.

Wayne D.

Ned, Nice lathe! Nice mounting of DRO & VFD also.