110V to 220V VFD

"Bob La Londe" fired this volley in news:nftn4s$o3q$1 @dont-email.me:

Just the 'doing it" part.

It sounds like a "sound" plan to me.

Lloyd

Can you use a 110:220 transformer, assuming the machine only has 120 V wired in it?

Or, maybe I'm totally missing the problem. Your existing spindle has a 110 V 3-phase motor in it? Or, is it a 220 V motor with a VFD that runs from

110 V?

Jon

Some VFD's are programmable for motor voltage, so the VFD could just have its parameter changed instead of swapping it.

Bob

I could, but I would still have to pick up a 220 VFD to replace the 110V VFD.

Yes.

No.

I forgot all about that. The machine has a 110V VFD. I suppose I need to see if I have a manual for it or if I can find one.

Caveat, I have never used or seen a VFD, But a standard 110:220 transformer will have very poor performance from 0 to 55 Hertz and probably just about as bad from 70 to 120 Hertz. Mikek

You would not use it on the output. You would use it on the input.

Oh! :-)

I just picked up a little Teco 1Hp VFD that takes 120V single phase in and puts out 220 3 phase. Surplus Center has them for about $150. I have not measured the output voltage, but the currents look right and the motor runs fine.

Good Luck, BobH

That little Teco would be perfect for a drill press speed control. Maybe not for my ideal current application (need 400hz and external control inputs), but I do want to convert my drill presses for speed control someday. I will definitely try to remember it. The price is right.

amdx fired this volley in news:nfu2cr$5b9$1@dont- email.me:

That's meaningless in this regime, Mike. VFDs don't work through a large iron core transformer.

When they need to boost or buck voltage at all, they do it through small, tightly-coupled, and HIGHLY responsive toroidal transformers -- one for each leg. And they respond rapidly, with small excitation current, and with almost NO DC impedance or current penalties.

Lloyd

I think that I might have implied the wrong thing. I meant that a VFD that is rated to generate 240v can be programmed to output 120. I don't think that a 120 output VFD can be programmed to 240 output.

Bob

Bob La Londe explained my Duh moment. On the other hand I don't see a single VFD schematic showing tightly coupled toroidal transformers. There my be a few series inductors, but nothing even showing transformers on the output. All I see are circuits with a DC buss and transistors directly driving the output. If you find something different, please post it.

Can you explain excitation current, DC impedance and current penalties, without referring to Google for corrections?

Mikek

I am no expert myself only having programmed 3 VFDs so far in my life, but I do recall voltage output being a programmable parameter on atleast one of them. I figured I'd pull the manual and see what I found. I went ahead and ordered the 110in/220out Hitachi along with a 220V spindle. I am using this machine daily to make money so I can't afford extended down time. I plan to have a spare spindle on hand at all times after I figure out the best application.

Greetings Bob, What brand spindle are you using? I'm intetested in adapting a high speed spindle of some sort for engraving on one of my mills. Thanks, Eric

I have two spindles from China ordered through Solar.Jean on Ebay. One is a

2.2kw 220, and the other is a .8kw 110. They both work fine, but are not currently installed on a machine. The .8kw was used briefly as a companion on the Hurco. It was also the main spindle on my Little Taig mill for a while. (The Taig is on a shelf doing nothing now).) The 2.2 was just powered up and run for a couple hours to test, and put back in the box pending completion of the machine its going on.

The one on the machine I am using everyday is a .8kw of unknown source. It came on the machine. It only has about 1000 hrs on it, but to be fair the cooling pump failed at some point so I have no idea how long it ran without coolant. Yesterday when I finished for the day it was making near constant noise. I can now feel the damage in the bearings when I turn the spindle by hand. Oddly enough it is still tight, and still spins up to full speed. It even still produces decent surface finishes. I did not power it up today. I've been busy all day doing secondary operations. Pinning mold hinges, installing alignment pins, putting on handles. That sort of thing.

I also have a 1.5kw 220V spindle from UgraCNC that was used for a while as a companion on the Hurco, and it worked fine, but it currently is waiting for me to finish the new machine it will be going on. It may be going back on the Hurco as a companion in the next few days as I have become very dependent on high speed spindles for 3D material removal rates with small cutters, and I have jobs stacking up.

So the Chinese spindles I see all over ebay work OK? They say they only have .005mm runout, is that true in your experience? Also, can I just use the coolant pump on the machine and pump water soluble coolant through the spindle or do I need to install a water only system? The mill I want to put the spindle on is a Fadal with the typical centrifugal coolant pump so the pressure isn't real high but there is lots of volume. Thanks, Eric

Yes and no. Some sellers seem to have better products than others. Stay away from the chepest sellers, those whose feedback listings are all private, those with low number of feedback, those who do not have feedback on the actual items you want to buy, and those with a disproportionate number of buyer to seller feedback.

I did buy one that was crap. It was a combination spindle, pump, mount, and tubing for a really good price. The spindle failed in veyr little time. Cheap bearings. Being my first one I destroyed the motor trying to repair it. It is what it is.

Most probably have that or better inside the spindle nose taper, but perpendicularity may not be perfect. The further your tool sticks out the worse it may be. Buying quality collets and closers from a decent source does help some. I try to only use stub length tools. I may even have some of the larger sizes I use custom made with short flutes and extra short shanks.

I would definitely not run cutting coolant through it. Many people run straight distilled water (** which will become slightly acidic over time with exposure to air). I run 50/50 automotive mix with its own pump and reservoir.

The mill I want to put the spindle on is a Fadal with the

That should be fine. Most people cool these with a small several hundred GPM pond pump. Your pump will probably put more coolant through it than most.

I would add that if you plan to do nothing but short job, light engraving you may even be able to run an air cooled motor, but the air cooled motors are open. You can't run cutting water soluble cutting coolant if you do. Even on the liquided motors the connector on the top is not water proof. After verifying proper operation I tape the connector and fill the backside with resin.

No matter what spindle you use I reccomened light fast machining approaches to keep load on the spindle at a minimum. I like to max in corners and stepover at 25% of rated spindle HP or less. They may in theory run their rated HP, but not for very long. For just shallow engraving a .8kw or even a .4kw spindle is more than adequate. HP calculations will show nearly zero.

Thanks for the info Bob. I looked for 62mm dia spindles like the one you described but only found 65mm dia spindles. Not that it matters. I will, at least at first, only be engraving with single flute engraving tools. I considered air cooled spindles but only briefly because of the coolant issue. I'll just order me a little pump when I order the spindle /VFD combination. I wanted to have a spindle that could be mounted in a CAT 40 tool holder and built myself a prototype out of a BLDC liquid cooled RC motor. It worked OK but I need to make some improvements and just recently an old customer returned who wants a lot of brass and parts engraved. He didn't know I could do this type of work and the huge range of fonts available. He gets stuff stamped with his text but it's expensive, especially if the font needs to be changed because a new stamp must be made. On top of that the folks doing the metal stamping keep the stamp. He saw some parts I had engraved for another customer and was bowled over that I could easily do this type of work because he really doesn't know what the capabilities of modern CNC are. Cheers, Eric