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VFD dust issues

Kevin Jenness

Kevin Jenness

Joined
Nov 15, 2020
Messages
843
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Location
Huntington, VT
A friend from my turning club said that he had burned out the vfd on his Powermatic 3520 due to dust buildup, and that he regularly blows the replacement out with compressed air. On reflection it seems a bit surprising that PM locates the vfd in a location relatively vulnerable to physical damage and dust buildup. I have three vfds in the shop, all in enclosures of some kind (in the headstock pedestal on my lathe) and I know that Oneway at least has theirs in an enclosure. How common is it for lathe manufacturers to do as PM does, and is it really an issue? I get the sense that the 3520 vfds are fairly durable. I would think it sensible to at least blow out an exposed unit from time to time to avoid overheating.
 
You do not want to use your shop compressed air to remove dust from a VFD. You should use a small can of compressed air to limit the
force of the air on the components of the VFD. You do not want to expose any static electrical charges onto the circuit boards inside the
VFD enclosure. If you use a small computer vacuum, it must be properly grounded at the nozzle to prevent static discharge. A shop vacuum
will create a static charge with the volume of air moving through the plastic suction line. Compressed air flowing through a polymer hose can
also create a static charge waiting to be released to a grounded component like a circuit board. You should always ground yourself when
working on circuit boards with various types of memory chips onboard.

Heat is the main cause of most VFD failures, some VFD's have air filters and cooling fans that need regular maintenance. Some VFD's require
air conditioning if they are in a high ambient temperature throughout the day. I have installed vortex coolers on a few of these where we had
compressed air readily available in the area. In an industrial environment small air conditioners mounted on electronic enclosures can be a
pain to maintain, the filters get plugged up continually and the compressors fail prematurely. The biggest drawback to a vortex cooler is they
use a constant supply of compressed air to create the cooling effect.

The other option is using a good quality VFD with a good heat sink designed into the enclosure to pull the heat away from the VFD.
The heat sink usually has external cooling fins that can be cleaned with compressed air to optimize the cooling of the enclosure.
 
I'm no expert on VFD's, but I can't imagine the Powermatic 3520 having heat buildup problems. I've turned for a couple of hours and the motor is just barely warm to the touch and the VFD isn't warm at all.
 
VFDs generate heat themselves and need to dissipate it. I don't know which model lathe and vfd you have, but commonly, the 3520 vfd is mounted to a ventilated aluminum chunk with fins, solely to get rid of the vfd heat. Other models of vfd have internal systems or even fans to dissipate the heat. Guess which one costs less? Yep, Powermatic made an economic decision to use a cheap vfd without an internal heat management solution. Oneway apparently made a different decision.
 
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The Powermatic 3520C's vfd has an internal cooling fan that runs after the lathe is stopped. When I am done for the day, I leave the power switch (under the vfd) on. The fan shuts off after a period of time (I have never timed it). I normally check the shop after dinner ... that's when I kill power to the lathe.
 
Mike Johnson said:
You do not want to use your shop compressed air to remove dust from a VFD. You should use a small can of compressed air to limit the
force of the air on the components of the VFD.
Click to expand...
What's wrong with turning down the output air from the compressor to 5psi? There seems to be nothing more wasteful to me than a can or air. A straw in your mouth is a second great option if you just need a puff or air. To get a can of air you have two factories involved plus lots of mileage for logistics and sales. I bet if you asked for a can of air in 3/4 of the world, you would get nothing more than a good laugh.
 
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