Dirt filled VFD

I found a large control panel in the local scrap yard and pulled a couple 5hp 460V VFDs. Also got a single phase 6KVA 440-220 V transformer. The VFDs had about a half a cup of water in each one. I pulled the covers off them and sat them in the sun to dry for a couple days. I wired up the cleaner VFD (Saftronics G5 which is a rebadged Yaskawa) to the back fed transformer and with some reprogramming, sure enough it ran.

I really couldn't power up the other one - here's a photo of the not so clean one (YASKAWA F7).



Figuring I had nothing to lose, I started pulling the boards (all 7 of them) until I had it down to the heat sink. I used a paint brush to gently brush all the dried mud - and it was on every board. Put it back together, not expecting too much, and plugged it in. Powered right up! About an hour changing parameters until I stopped getting error codes, and then it was running the motor nicely too. A photo of the cleaned internals:



And a photo of the transformer, the newly cleaned VFD, and the 550 V motor that will soon be going back on the tool and cutter grinder now that I have a power source.



The back fed transformer is putting out right around 500 V. The max input setting on both VFDs happens to be 510V, so I figure it will work nicely for feeding 550 V motors that are common on older Canadian machine tools, and you can set the max voltage down to 440 for American made equipment. Now I just need to find (or build) another 220-440V transformer to feed the other VFD. Oh - just about forgot the price. $27 for the transformer, 5 for the cleaner VFD, and nothing for the dirty but newer and nicer one!

Wayne

Nicely done. I have reclaimed (out of necessity) some 2300V 2000HP VFDs that went through total submersion in mud after a flood and landslide. What I did was to put all of the PC boards in my dishwasher, no soap, and run them through 3 cycles, but on the last cycle I poured distiller water into the tub of the dishwasher rather than let it fill with tap water. I let them air dry (no heat in the dishwasher), packed them in rice and baked them at the lowest oven setting, in my case 150F, for 6 hours. Everything worked fine, the drives fired right up!

Mind you, nobody was willing to stay in the room with me when I energized them. I can't understand why...

Side note, did you (hopefully) reform the capacitors by applying low voltage and increasing it slowly? Saftronics drives that were Yaskawa are around 15 years old at least, and if unpowered for a long time, the caps inside would degrade. If you did not reform them, they may work fine at first but may not last long. If not, it's too late and it is what it is, but at that price, you can replace the caps and still be way ahead. But if you get ANY kind of voltage related fault, power it off before there is collateral damage.

+1 for Waynes!

Excellent work, Waynes!

Cleaning out dirty electronics isn't incredibly complex... a carefully-distanced pressure washer is my tool for cleaning out welders... much easier to sort out wire numbers when they're not covered by a quarter-inch of crud, and as J noted, the key is getting it dried off.

The first time I ever used a pressure washer on a VFD, it was a little smaller than the one J noted... it was a traction inverter for a light-rail vehicle that 'turned left in front of an oncoming car'. After the lawsuit settled, they put the LRV into a rehab program, and I took on the task of showing the guys how to restore it to full operation... and like your Yasks, the driver and interface boards were all covered with dirt from the inverter case being bent too much to stay closed.

On that one, I started with a vacuum cleaner and sucked the worst of the loose debris out. This one is about the size of an average coffin, with big hockey-puck solid state devices (I don't recall if they were GTO or IGBT, but same idea). The busbars were all bent, some of the insulators shattered, and there was a 2" puddle of water along one of the corners. Fortunately, the card connectors weren't corroded.

After I got the leaves, water, beechnuts (?) and dead insects out, I hit it with a pressure washer from about 4 feet, which loosened most of the rest of the dirt. Like J noted, once the cards are out, a trip to the dishwasher is next. I used the one in the facility lunchroom during 3rd shift so as to not ruffle feathers. (aside note, a few days later, one of the shop wrenches brought in a portable that he'd recently taken out of his house, and it worked out great, so keep that in mind if you come across a portable that someone's replaced with a built-in)

VFDs have high-freq circuits, so make sure all inductive elements are dry... and dry underneath each IC, particularly IC sockets. Don't use compressed air... the proportionately cold output will cause condensation to go where you're trying to blow moisture out... and most of the time, there will be oil or other debris in the hose.

A hair-dryer does a good job of taking care of the stray moisture... followed by a close inspection of all componentry. There's rarely anything on circuit boards that is adversely affected by water... the biggest issue, is anything that is IN the water... alkalines, acids, petroleums, salt... all bad stuff that you need to get out of there. Every so often there'll be a relay that might pick up water, pop the cover off and dry it out, or if it's on a socket, take it off beforehand, and get a spare on-hand just in case.

The worst, is corrosion on electrical contacts, and the second worst, is moisture that gets into one end of a conductor, and creeps up into the wire a ways where you can't see it.

If it was clean and dry when it was shut down, and clean and dry before you power it up, it should be okay... bring it up easy, and stand near the switch.

Oh, and another handy tool I just remembered... Water-Pik!

DaveKamp said:

There's rarely anything on circuit boards that is adversely affected by water...

Click to expand...

When not energized... important distinction. (I know you mentioned it later, I just thought it's worth repeating for emphasis.)

The first time I figured that out was after watching the process of assembling PC boards, after which they went through what is essentially... a dishwasher.

Thanks guys,

I did not reform the caps, as I didn't think the control panel the VFDs came from had been out of service very long. It wasn't in the scrap yard for more than 3 weeks, as it wasn't there on a previous visit. I did think about it, but from what I've read, it's only applicable for post long term storage. Of course I have no idea how long the control panel had been in the factory before it was scrapped.

I considered washing them with distilled water, but the dirt was fully dried out so it came off very easily dry. My biggest concern was causing static damage to the CMOS components. I really don't know how easily that happens.

Turns out the single phase transformer is 3 KVA, not 6. Still plenty for most of my motors I could use this with. One of the VFDs will be set up with to run the 1/2 hp 550V motor on my Clarkson tool grinder - the single phase motor I put on gives a very poor finish. I'll probably set up the transformer and VFD as a roll around unit as I also have a small surface grinder this could feed. Both will need to be rewired to bypass their switches and use the VFD for control.

One of the workers was watching me pull the 2nd VFD and asked if there's any chance it will work (after seeing me dump water out of it). I told him it probably wouldn't, but it was worth the 5 bucks just for the fun in trying.

Wayne

Hmmm... you MIGHT be able to get 6kva of capacity out of that 3kva transformer IF you wire it up as an autotransformer... in 'boost' configuration. I drew up something like that several years ago, and wired it on a test bench just for grins, and it did seem to work okay, but never needed it, so I can't say how well it performs under a working load...

Oh, and thanks for including the clarification, J- yeah, I meant 'when not powered up'.

I used to use dishwashers to clean up chassis of old tube transmitters and receivers... and the oven on WARM to dry 'em out... until SHE caught me at it...