Testing a 380-480V 3 Phase VFD with 240V Single Phase
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    Default Testing a 380-480V 3 Phase VFD with 240V Single Phase

    I ended up with a 380-480V 3 phase VFD. I have no use for it but it was cheap so I bought it. Figured I can eventually trade it for something I need.

    It was suppose to be new but it's used. For the price I paid that's OK, but now I need to test it, something I didn't think I would have to do.

    The only power source I have is 240V single phase. Can I at least test to see if it turns on without damaging it? From what I've read I believe I can, but thought I'd check before doing so.

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    It may not turn on. When testing those, I have always used a "4 way" transformer, 120/240 to 240/480. other than that, no damage from a basic test of turn on and run. Some can refuse to work if they get 1 phase in, and some may refuse to work with no load on output.

    We always use a "CMOS motor", a very low power motor of the right voltage, so as to verify actual operation. Which remonds me, we do not currently have a good low power motor, and I need to find another. They are not common.

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    I worked with some Toshiba 380-440 V VFDs.

    They would safely light up the control boards at 240V. But would fault with a "low voltage" display.

    I used a variac (tandem unit for 240V) to boost the supply. The units went fully functional at 320V.

    Like JST I use a small motor to test output and control. In my case a Minarelli Delta- Wye wound 2-3 amp unit. Cute little guy ;-)

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    Thanks. I don't have a small motor and was just hoping to see the display light up. At least that would give me some hope that it's working.

    Long day today but I'll give it a try tonight if I get home early enough.

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    Just a word of warning, if it has been sitting around with no power on it for 2 or more years, you could damage it just by connecting power to it. See if you can determine how long it has been since it has had power applied. If 2 or more years, you need to be VERY careful about SLOWLY increasing the voltage to the drive over the course of hours (called "capacitor reforming"), something most people are not equipped to do.

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    Quote Originally Posted by ptsmith View Post
    Thanks. I don't have a small motor and was just hoping to see the display light up. At least that would give me some hope that it's working.

    Long day today but I'll give it a try tonight if I get home early enough.
    You don't need a lot of CURRENT, given no or low load will do to light-up the controls & display panel (usually a derived 24 V or thereabouts critter..).

    Even a small Variac - handy to have in any case - PLUS a small boost transformer can give you the range to reform the caps.

    Texas is too far away for you to help me get shut of close-on 400 lbs Avoir of an all-copper elliptical-coil R.E. Uptegraf 240 <=> 480 V Delta-Delta transformer once intended to run a 10 HP Altivar 71, but the bugger is surplus because I chose to NOT run AC voltages above "300 Volt Class", nor Delta, either one.

    IOW.. with need of some serious transformer-fu to put it to WORK, just WTF do you plan to DO with this VFD, even if it is in decent working order?

    I simply pitched the Altivar. It was "owed" all-new capacitors. That made less economic sense than writing it off, outright did.

    YMMV

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    Quote Originally Posted by Jraef View Post
    Just a word of warning, if it has been sitting around with no power on it for 2 or more years, you could damage it just by connecting power to it. See if you can determine how long it has been since it has had power applied. If 2 or more years, you need to be VERY careful about SLOWLY increasing the voltage to the drive over the course of hours (called "capacitor reforming"), something most people are not equipped to do.
    The Variac came in handy for the reforming process on the Toshiba units as well.

    I started at <50V and bumped the voltage up 30 or 40V every couple of hours until Mains voltage was reached. (240V at my place) Then I reconfigured for over mains boost.

    I did not know if the units needed the reforming, but one of them is still in service today, In fact it is powered up right now. Trouble free for about ten years IIRC.

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    If all you have is a 4 way transformer, going in with 115 on the 480 winding, coming out the 240 and leaving that for 30 min or so, then 115 into 240:240 winding, leaving that for 30 min or so, then the same on 240 input, and finally going in with 240 to the 240 winding and out on the 480 will do a decent job in most cases. It steps up the voltage in reasonable increments.

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    Quote Originally Posted by CalG View Post
    The Variac came in handy for the reforming process on the Toshiba units as well.

    I started at <50V and bumped the voltage up 30 or 40V every couple of hours until Mains voltage was reached. (240V at my place) Then I reconfigured for over mains boost.

    I did not know if the units needed the reforming, but one of them is still in service today, In fact it is powered up right now. Trouble free for about ten years IIRC.
    Agreed, but most people don't have a variac. I had one for years that I got at a flea market for $5 but it was stolen. I've been plumbing the depths of Craigslist and garage sales to buy another one, but people have caught on as to how handy they are to have around and the ones that go up for sale are overpriced or some cheap Chinese stuff that I don't trust.

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    Quote Originally Posted by Jraef View Post
    Agreed, but most people don't have a variac. I had one for years that I got at a flea market for $5 but it was stolen. I've been plumbing the depths of Craigslist and garage sales to buy another one, but people have caught on as to how handy they are to have around and the ones that go up for sale are overpriced or some cheap Chinese stuff that I don't trust.
    They are all over eBay, "grand old" US makes most of all.

    Both of my small ones came in the door with Precise grinders. The big one is Chinese, bought new. Gets the job done.

    How easy is it to screw-up the build of a Variac? And why would anyone expect a US firm to bother to make such low-tech, low-volume, uber slow turnover items in the USA, present-day costs and burdens?

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    I've actually owned a couple of Variacs over the years. I use to buy and sell used musical instruments for a living. Eddie Van Halen used Variacs to lower the voltage to Marshall amps to get what he describes as the "brown sound". In guitarist circles Variacs would bring $100 easily. So I came across a deal on one and bought it for resale. Luckily I didn't try the Marshall trick because I thought you raised the voltage, not lowered it, and was afraid to try it. This was a common misconception and supposedly many Marshalls were damaged because of it. Apparently Eddie knew of this, but thought it was funny, so he never revealed that he was lowering the voltage. At least that's what I heard.

    The last 10 years I've owned a pawn shop and bought another Variac about a year ago. Sold it on Craigslist for ~ $75.

    Now that I could actually use one for the first time in my life I don't have one.

    Thermite, to answer your question as to what I'm going to do with it, I'm going to flip it, either for trade or cash, because that's what I've done for a living for over 30 years.

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    Thanks again.

    I have a decent variable DC power supply that goes up to 30V or so that I use for a slot car track. Then I could do 120V AC and later 240V as ya'll suggest. I can to that tomorrow night.

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    Quote Originally Posted by thermite View Post
    T

    How easy is it to screw-up the build of a Variac? And why would anyone expect a US firm to bother to make such low-tech, low-volume, uber slow turnover items in the USA, present-day costs and burdens?
    Variacs (Trade name, by the way, like kleenex ;-)) have rather information dense resistive carbon wipers to accommodate spanning multiple windings and the attendent "circulation".

    Sounds like something easily under engineered when copycat market pressures are dominant.

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    Quote Originally Posted by Jraef View Post
    Agreed, but most people don't have a variac. I had one for years that I got at a flea market for $5 but it was stolen. I've been plumbing the depths of Craigslist and garage sales to buy another one, but people have caught on as to how handy they are to have around and the ones that go up for sale are overpriced or some cheap Chinese stuff that I don't trust.
    I have a few, I get 'em for a couple bucks at estate sales. Dirty ones go for cheap. Nice shiny ones cost money. All of them work the same, and there are rags and water everywhere.....

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    I'm not sure how this degraded into a political septic field, but the original poster's question didn't deserve it.

    To test a 480v unit on 240 single, is simple, as many of our simple posts identify. I actually run all my 480v VFDs on single phase, from 120 or 240v mains using a dry transformer wired backwards- primary to the source, secondary to the VFD.

    To just test to see if it powers up, you can use a 250vA control transformer, just so long as it has a 120/240v secondary and a 240/480 primary... as it was noted above... '4 way'. If you don't have one in your shop, it's time to get one, because it is a veritable 'swiss army knife' for electrical testing and isolation.

    Many VFDs will run on single phase... there are some that just won't, and some that're smart enough to complain ("Phase Loss Protection"). There's also some that'll complain, but the fault can be disabled. If you wanna RUN it on single, just make sure that you don't load the VFD over about 50-70%, because the VFD's input rectifiers and capacitors will be under a fair amount of strain... rectifiers from the higher current-per-leg, and capacitors from the ripple.

    While capacitor reforming IS a valid concern, I've NEVER been in a circumstance where it was a problem with any of my VFDs... and ALL of MY VFDs were surplus pull-outs that came to me on a pallet, and I paid mebbie ten bucks a piece for 'em. Not a single one got reformed, and the only ones I wasn't able to use, were the ones that were smashed in critical places, or missing desirable pieces....

    But if you MUSt reform (and I have done it with many of my antique radios)... just creatively wire the VFD's power supply in series with a common incandescent lightbulb... start with a 3w nightlight, leave it on for an hour or two, then switch to 1 15, then 30, then 50, then 100... then go to full power. It'll either be fine, or it'll die.

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    I just saw this. Thanks Dave. I just bought a control transformer as you described. As you say, I'm sure it will come in handy for testing other things as well.

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    Quote Originally Posted by ptsmith View Post
    I just saw this. Thanks Dave. I just bought a control transformer as you described. As you say, I'm sure it will come in handy for testing other things as well.
    Yep, they do. They're great for wiring 1:1 to provide isolation from mains for testing electronics that might be... 'leaky'... and it's always nice to have the wiring options to put power at whatever range you can dream up.

    You might well find, that after messing with that VFD, that you like how well it does what it does, and that you've got just-the-perfect-use for a full variable drive system. You might find that after converting one machine to use that VFD, that your other machines need that same improvement...

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    You're preaching to the choir. ;-) I have 2 Hitachi VFDs that are single phase input. So I have no use for this one and only bought it because it was a good deal. Or at a least I think it was. Maybe not seeing how I was the only bidder.

    WEG VARIABLE FREQUENCY DRIVE CFW700A13P5T4DBN1 7.5HP VFD 380-480V NEW | eBay


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