Some Schneider 3 phase VFDs can't be run de-rated on single phase. Why would that be?
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    Default Some Schneider 3 phase VFDs can't be run de-rated on single phase. Why would that be?

    I have a 15HP 3 phase ATV212 that I was going to use to run a 5HP single phase motor. Some Schneider VFDs are not rated for that, including mine. "The ATV212 is not capable of supporting single phase input applications." It does have the option to disable input phase loss detection, but the manual says it's for training purposes only, with no motor load.

    Any idea why that is? The VFD rating is triple the motor rating, and I don't have any other use for it, so I'm temped to try it anyway.

    Need assistance selecting the parts required for single phase input to a VFD to run a 3 phase motor.

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    Don't some connect a capacitor from L1 or L2 to the third phase input of the VFD. Not perfect 3 phase. So.

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    Quote Originally Posted by ptsmith View Post
    I have a 15HP 3 phase ATV212 that I was going to use to run a 5HP single phase motor. Some Schneider VFDs are not rated for that, including mine. "The ATV212 is not capable of supporting single phase input applications." It does have the option to disable input phase loss detection, but the manual says it's for training purposes only, with no motor load.

    Any idea why that is? The VFD rating is triple the motor rating, and I don't have any other use for it, so I'm temped to try it anyway.

    Need assistance selecting the parts required for single phase input to a VFD to run a 3 phase motor.
    Rest of the goods can't stand the ripple is why. Just like they said. My older Altivar 71, no longer even spoken of, could do. OTOH, it was a 380 - 480 VAC critter or get f****d, and the big-ass R.E. Uptegraff 15 KVA transformer is now holding down the driveway after five or so years of holding down the back patio.

    I threw ALL the Vee Effing Dees away in favour of RPC, Phase-Perfect, and faaaaar longer-lived Dee Cee drives.

    Not sure it is WORTH it, cheap as the many and several built-for-single-phase VFD can be, but you can build an external replacement to provide smooth-enough DC and at high-enough power to introduce it onto the VFD's "DC buss" thereby replacing the function of a VFD's original front-end rectifiers and capacitor bank, input section outright.

    Not terribly expensive. Just bulkier by 3 or 4 times the space the OEM built-in used.

    The "back-end" that generates and manages the synthetic 3-P fake-sine wave output will no longer give a damn where it got good, clean, and plentiful DC from. So long as that is exactly what it DOES get.

    That part does NOT assure the rest of it as actually the best choice of VFD to run a machine tool, however. The Altivar 71 was. Others were better at running HVAC air-handlers instead.

    I haven't looked at VFD much since scrapping them. They are ONE pain in the ass relegated to the rear-view mirror. Still working on a few more OTHER nuisances, here and there, but VFD are some other sufferer's annoyance now.

    Good luck with it. Do drop us a postcard if you find a real job. Or even a woman that buys her own shoes.


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    The units are fairly small sized for their power range. That, to me, suggests they have limited filter capacitance in them.

    That's fine for 3 phase, which has a maximum of 14% ripple voltage, the voltage of rectified 3 phase never goes below 86% of peak. Single phase goes to zero, and is low for an appreciable part of the AC cycle.

    The capacitance is enough to do fine with the low ripple, and high ripple frequency (180/360Hz for 3 phase 60 Hz input). It is likely not enough to even start to be suitable for single phase 60/120Hz ripple.

    It's a perfectly good way to make a VFD, and can even eliminate the use of electrolytic capacitors, which is great for low temperature operation (MIL).

    Absolutely no good for 60 Hz single phase.

    I did design a unit for MIL use that was done like that. 3 HP unit, good for nearly zero HP on single phase. Which was fine, that 3 phase input was in the spec.

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    Thanks JST.Interesting post. I don't know how big the average 15HP VFD is, but I thought mine was pretty big. 25lb and dimensionally pretty large. But I defer to your knowledge and experience. I don't think I'll try it.

    d11m3x.jpg

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    I looked in the manual (at Schneider). There were two possible sizes for that power of unit, the smaller one is what I assumed. The bigger might have more stuff. Or it may just be that they switch to a new "frame size" and "heatsink size" at that point.

    Size was unclear to me, since both ranges seemed to include your power level, so it could have been either size.

    In any case, that bus capacitor thing is a good reason why a VFD might not be capable of ANY single phase operation.

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    If you over size it enough, it should work. The "enough" part is something that the mfr has to agree to though. Lots of people ASSUME that 50% de-rate is fine, because it IS fine on SOME drives, especially those with a DC bus choke. But on smaller-cheaper little "throw away" drives like this, that's usually not enough. As a gross general rule, I use a 65% de-rate on unbuffered drives (unbuffered means no DC link choke). This by the way is the case with Allen Bradley PowerFlex 520 series drives; the de-rate for single phase input on a 3 phase drive is 65%, because the capacitors will also get significantly hotter. With the PowerFlex 7 class drives that have a DC choke however, the de-rate is 50%.

    So why will Schneider not do that? It could be that instead of tapping off of the VFD's DC bus and using a DC to DC chopper to derive internal control power for the electronics, they use a separate AC/DC power supply and on a 3 phase drive that is a 3 phase rectifier as well, plus it is always the exact same power supply board regardless of the size of the drive, so even if you de-rate the drive, the internal power supply board is NOT rated for a single phase input and the drive will fail prematurely because there is too much ripple on the CONTROL bus. I'm speculating here though, I don't know if that's the real reason.

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    "But on smaller-cheaper little "throw away" drives like this, that's usually not enough." Why would you say that about Schneider drives? They're on the higher end of the price spectrum.

    In the past someone made the same comment in a thread I started about a Weg drive, which also aren't cheap drives.

    I guess there's too many different brands to be familiar with all of them.

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    It's usually a matter of drive series, not drive manufacturers.

    And power ratings.

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    Quote Originally Posted by ptsmith View Post
    I have a 15HP 3 phase ATV212 that I was going to use to run a 5HP single phase motor.
    You want to convert 240 single phase power to 220 3 phase power to power a 240 single phase motor? Why not just run the single phase motor off of single phase 240?

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    Quote Originally Posted by metalmagpie View Post
    You want to convert 240 single phase power to 220 3 phase power to power a 240 single phase motor? Why not just run the single phase motor off of single phase 240?
    I saw that and figured it had to be a typo....

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    I’ve wondered if some vfd’s might check to verify input on all phases. I haven’t run into any but does anyone know if some do and if so could this be another reason?

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    Quote Originally Posted by ptsmith View Post
    "But on smaller-cheaper little "throw away" drives like this, that's usually not enough." Why would you say that about Schneider drives? They're on the higher end of the price spectrum.

    In the past someone made the same comment in a thread I started about a Weg drive, which also aren't cheap drives.

    I guess there's too many different brands to be familiar with all of them.
    You might look at the Groupe Schneider history and go "WTF?"

    They tend own top-end, middle-market, AND bottom-end el cheapo competitors in the same marketspace, and all at the same time! Altivar is not even their only line of VFD any more than Square-D is thier only line of switchgear and protective devices. Weg is ALSO a broad-market maker, and economy goods more than not.

    Smaller picture the Altivar line alone is stratified into several different types of VFD, only a FEW even intended for machine-tools. To an extent, that is the case with MOST makers.

    As said arredy - it isn't JUST the Company, it's also the product line, and then, the model families WITHIN the product line. And even one model to the next.

    Page TWO:

    VFD's, are too inexpensive to waste the hours of your life trying to outsmart a Design Engineer whose work at tailoring a unit for a narrow range of uses was meant to serve its target by the multiple thousands and multiple tens of thousands of units ..whilst YOU fiddle-f**k about ... with just the ONE.

    Much wiser to peddle the unit to whomever can use it AS IS.. and go find yourself another that YOU can use AS IS.

    See also gender reassignment surgery for another pain vs gain example.

    Then make up your mind and JF "Go for it".

    Either one.

    "Easy for YOU to say!"

    Surely it is.

    I am not he who actually has to give a damn about your choice!

    The way things are going in this country?

    Day may come we see VFD's in the supermarket.. same aisle as six-packs of penises and vaginas by the dozen.

    You'd have to know mass-marketing and cheaper in volume?

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    Quote Originally Posted by Rob F. View Post
    I saw that and figured it had to be a typo....
    Yes a typo. I didn't realize it until now. I meant 3 phase motor.

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    Quote Originally Posted by Pete Deal View Post
    I’ve wondered if some vfd’s might check to verify input on all phases. I haven’t run into any but does anyone know if some do and if so could this be another reason?
    Yes, many have "input phase loss detection". But most allow you to disable it, including the drive I have. So that doesn't appear to be the reason.


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