Have VFD ratings grown to handle 220V 1ph to 3ph for a 5HP motor?

O great electron gurus,
Excuse my ignorance, but when I set up my Bridgeport about 7 years ago, a 1HP VFD for 220V 1ph to 220V 3ph was about the limit. I will plead that I was ignorant even then and just got lucky that the TECO unit I got, has served me well. At the time, I recall the rule of thumb was that a VFD de-rated the motor HP 75% and has never posed an issue. When I bought my 14x60 lathe, the 5HP motor left me with no option but to purchase a rotary phase converter. That worked great, although I still have no idea how I managed to successfully wire it up. Long story short, I just made a trade for a smaller 14x32 Takisawa, but it's still a 5HP motor (two speed). I realize I could just keep the RPC and not worry about a thing, but curiosity gets the better of me.

So as the title suggests, are VFD's successfully producing 220V 3ph output from 220V 1ph input to satisfy the power needs of a 5HP motor? I now see some VFD's listed that appear to perform this task, but since I have a distinct aversion to rampant electrons, my doubts exist that these can be trusted. This isn't a cost based question, just a matter of whether they exist and function. I am just running equipment for light duty, non-production work at home to feed my desire for making chips out of perfectly good metal. I will appreciate feedback for pros and cons, along with any known good manufacturers that work as advertised. I have tried several search terms here on the forum, but have yet to find a similar inquiry, so my apologies if this is a topic that has been clearly discussed.
Thanks

Mark

My 5hp lathe is running on a 220v single phase to 220v 3 phase 5hp Dan Foss VFD. Works great.

rustytool,
Thanks for the reply. Okay, so this isn't a unicorn. I quickly was overwhelmed by the Danfoss site. This is why I have had such difficulty narrowing down what could work. If it's not too much to ask, could you provide more detail as to the specific model and part number. That way I have a baseline to compare specs between manufacturers. I'll keep trying to educate myself, but the extent of choices can make you dizzy when you have zero background in the field.
Thanks

Mark

Really, VFD's don't need to be "designed" for single phase input at a particular maximum rated horse power. Buy a bigger one!

Just be fussy about any "loss of input phase" nonsense.

I like the Toshiba Tosverts. 20 hp or so.
The 7.5 hp lathe, and the 5 hp air compressor each run on such.
5 hp units drive 2-3 hp motors on other machines.

All with single phase input.

CalG,
Okay, I'm missing something obvious, so please bear with me. I appreciate the info, but feel dumber than when I started. The key factor here is that the drive has to be made to receive 1ph input power, correct? It seems like every example I find, except for some dubious Chinese listings on Fleabay, complete with poor English, are all built to accept 3ph input. I have gone to the Danfoss site, Seimans and now Toshiba. I might as well try to read hieroglyphics. I warned you that my relationship with electrons is dubious and to me it is akin to black magic. I have tried to find a selection chart that would allow me to drill down to applicable choices, but no luck so far. That's why I inquired about a specific part number to reverse engineer it.
Thanks

Mark

Mark

Bottom line is that a VFD's first function is to "rectify" Incoming AC into DC so the DC can be controlled via semi-conductors of all types. Semi conductors and AC do not play well together.

So bottom line for a useful VFD is as long as it is "dumb enough" to rectify either single or three phase line power without throwing some phase detection fault (I have not run across one of those yet, perhaps someone with more experience with differing brands and makers will add examples), AND the VFD has sufficient amperage rating to handle the current both on the way in and the way out (even more doesn't hurt, and helps for functions like DC injection braking). The VFD will power your motor "jess fine".

So get a good used industrial 10 HP drive and supply it with 220 V single phase to run your 220V three phase motors!

NB VOLTAGES MUST MATCH! i.e. a 220 Volt VFD MUST be fed 220V (200-240v anyway) No VFD likes to have it's voltages mixed up. Motors on the other hand have some handi relationships. ;-)

CalG,
If I am understanding correctly, you can feed a unit marked as 3ph input with single phase and it will still work? There is no shortage of 10hp drives set up for 220V, so that seems almost too easy. If that is the case, THAT! was what kept crossing me up, I was under the impression that the inverter had to be designed for single phase to start with. Do you just leave an input leg open?
Thanks

Mark

As I study this more, I realize that the lathe I just traded off could have used a VFD due to a single speed, one direction motor. However, the one I have now, would become problematic, due to having a two speed reversible motor and the RPC is actually well suited. I now see where it is frequently brought up that it isn't good to have anything between the VFD and a motor. Losing the forward/reverse lever and being limited to the VFD control panel would be awkward. So now I know more about this and it makes sense why my mill never posed a problem. Obviously one of those situations where God watches over idiots and small children. I really appreciate the input. My curiosity of how things work often leads me down the rabbit hole.
Thanks

Mark

Just in passing

Two of my lathes that are driven by VFDs, with single phase input, are full functional with the apron controls etc. It did take some "playing with electrons" to get all the wires ending up in the correct places, But these Variable Frequency Drives "can do it all"!

I've never seen a 3 phase electric motor that was not reversible. It must have been something special. ;-)

CalG,
That wasn't a typo, the lathe was a Graziano SAG14. You would turn on the motor and it ran at speed in one direction waiting for the clutch drive to be engaged. Forward and reverse were through the clutch drive. It definitely could be wired to turn in the opposite direction, but not needed.

I wish I had the electrical background to feel comfortable trying to wire it up, but I am a realist and would likely succeed only in ruining a nice VFD. Since I have no contacts in the professional machinist realm locally, I am forced to reach out to those such as yourself that are willing to provide help and I appreciate it. I like the thought of something a bit tidier than 100lb RPC, however to accomplish that would require unfairly asking for a lot of help for me to chase windmills. In all fairness, I already have the RPC, it's simple and somehow, I have managed to make it work all these years. IF, you were foolish enough to volunteer your help, I would shamelessly beg for the opportunity to pick your brain for guidance on those pesky little bits with the electrons, if you wanted to get involved in my folly. Thanks again, for the information you have shared.

Mark

Plain and simple what matters is the drive rating. Some drives are designed for single phase input, some three phase and others both. Read and follow label directions and live a happy life.

mike

following the label directions is so boring!

Sure, there are no disappointments, but there are no moments of adventure, excitement, and success either.

What is the bumper sticker? "Good girls don't make history"

If a VFD has a three phase designed input, it is Derated by about 50%. All VFD's are designed for three phase originally. Some manufactures (about a dozen) have jumped on board and implemented single phase to three phase VFD's on the same platform. When I pull the boards apart this is the only difference. Look at the white silicone with the jumping ransistors or whatever they are. These power from R to S. R and T are the single phase input.

This 5hp SP VFD has been running for two years. The IGBT folded and the whole board is getting replaced under warranty. I don't have to send the whole VFD in to get it analyzed/tested. The nice thing is is some VFD the manufactures make it possible for Re and Re. Others don't.

Edit; I can get a single phase VFD that is non-custom for up to 15 hp.

Matt Matt said:

If a VFD has a three phase designed input, it is Derated by about 50%. All VFD's are designed for three phase originally. Some manufactures (about a dozen) have jumped on board and implemented single phase to three phase VFD's on the same platform. When I pull the boards apart this is the only difference. Look at the white silicone with the jumping ransistors or whatever they are. These power from R to S. R and T are the single phase input.

Click to expand...

looks like gimmickry to me. not sure why those components are needed, especially if they are only connecting an unused diode to the other when used on single phase. if single phase is supposed to be from R to S then they make sense. one is an MOV, the other is a 2.2 or 4nF capacitor.


anyhow as i replied to the other thread.. capacitors aren't cheap. the difference between single phase and three phase is about a 2 fold increase in ripple current demanded of the capacitors. that's why you need the 50% derate.

the second reason is the diodes. you would have a 57% derate for the diodes alone, but they are oversized anyway--however the power factor is worse with single phase and the diodes themselves have a little bit of resistance.


anyhow, the mythical 100-150$ single phase rated, 3hp VFD. yes, they work. for maybe a thousand hours at full load. when the capacitors blow up and you size proper ones that will last for 10 to 100,000 hours, you'll find they cost more than the vfd did.


anyhow, there are a lot of VFDs running around that have no "snubber" or film capacitors located anywhere near the igbt. you can save a couple bucks by leaving them out.. until the electrolytic capacitors dry out and their esr increases to the point the igbts blow up..


or you can save a few dollars on the electrolytic capacitors by making the snubber capacitor larger.. only problem being when the electrolytic capacitors dry out due to being run on single phase.. you find that your motor has a 120hz beat frequency all of a sudden. most people will never notice.

--edit: to some extent you don't even need capacitors on the dc bus, if the snubber capacitor is large enough to contain the total energy stored in the (bad) power factor of the motor.. which might be 10-30uf/hp at 240vac. --you just end up with a really massive 60hz torque ripple in the motor.

induction cook tops for instance (as a general rule) do not have any electrolytic capacitors, that's why you can hear and feel the 60hz ripple in the pan..

Matt, johansen,
Excellent info, although at a couple of points my head threatened to explode. johansen brought up an excellent point "the mythical 100-150$ single phase rated, 3hp VFD. yes, they work. for maybe a thousand hours at full load" In the environment of my home shop and with the light duty that the lathe will see, I am the least likely to test the limits of any unit. The way my VFD is set up on my Bridgeport, it's hard-wired and powered 24/7, so it acts like a constant standby power supply/ON switch for the mill.

My stumbling block to understanding is that I was traumatized by being an Electronics Technician during my time in the Navy. I managed to get DC concepts down pretty well because SATCOM and HF radios run on DC internally, but the whole AC theory eluded me. I tried to cross-rate, but somehow they thought I was a great ET and wouldn't let me go Gunners Mate. I still deal with electrons to a moderate extent with the gun systems on the ships, but it's primarily hydraulics and mechanical work. Part of me likes to geek out on technology when I can understand it, or get off my butt to catch up. After all these years, I'm finally going to pull the trigger and set this "new to me" lathe up with a 2 axis DRO. Since I am stripping this thing almost to parade rest for cleaning and repainting, my mind turned to potential upgrades and the VFD concept made me start thinking it could be a worthwhile change.

If it was as simple as connecting the cord and running it, I would be glad to remain blissfully ignorant and go for it. If going through the switches and relays would create headaches, I don't feel it's worth playing mad scientist since my AC diagnostic skills are lacking. I will still be glad to hear any further input to build up the limited knowledge I have on this subject.
Thanks

Mark

Me again,
Okay, I'm going to dredge up my older thread. Thanks to the previous input and information provided by the members here, I have been trying to study up and become a bit more competent with VFD's and a few things have come to light that may make this a viable reality. So if I have studied this and have it right.

1) I can wire the VFD directly to the high-speed on the motor and not utilize the low speed since speed control would be governed by the VFD and would prove unnecessary.

2) I can wire the forward/stop/reverse lever directly to the VFD as an external control input to bypass the keypad for those functions.

3) With an appropriately sized resistor (~300W, 40ohm) added to the VFD, it can act as a brake (when programmed for deceleration)and make the mechanical footbrake redundant, or at least a backup mechanical fail-safe.

4) I can wire the footbrake switch to kill power, acting as an E-stop.

5) Eliminate all other switch functions on the lathe and remove the relays (power on, low/high and the unused coolant pump).

One significant question remains, would I be okay to run 220V 1ph direct to the VFD, or would I be better off to run my RPC to the VFD to provide 220V 3ph? If so, would want to purchase an over-rated VFD for 1ph input, or a 5hp rated using 3ph? I won't lie, if I can eliminate the RPC from the equation and still safely power the system, that would be the preferred outcome. I would appreciate any feedback to confirm that I'm on track and not being a misguided fool.
Thanks

Mark

CalG said:

Mark

Bottom line is that a VFD's first function is to "rectify" Incoming AC into DC so the DC can be controlled via semi-conductors of all types. Semi conductors and AC do not play well together.

Click to expand...

You did tell this to your audio amplifier , did you ?

Crank said:

Me again,
Okay, I'm going to dredge up my older thread. Thanks to the previous input and information provided by the members here, I have been trying to study up and become a bit more competent with VFD's and a few things have come to light that may make this a viable reality. So if I have studied this and have it right.

1) I can wire the VFD directly to the high-speed on the motor and not utilize the low speed since speed control would be governed by the VFD and would prove unnecessary.

2) I can wire the forward/stop/reverse lever directly to the VFD as an external control input to bypass the keypad for those functions.

3) With an appropriately sized resistor (~300W, 40ohm) added to the VFD, it can act as a brake (when programmed for deceleration)and make the mechanical footbrake redundant, or at least a backup mechanical fail-safe.

4) I can wire the footbrake switch to kill power, acting as an E-stop.

5) Eliminate all other switch functions on the lathe and remove the relays (power on, low/high and the unused coolant pump).

One significant question remains, would I be okay to run 220V 1ph direct to the VFD, or would I be better off to run my RPC to the VFD to provide 220V 3ph? If so, would want to purchase an over-rated VFD for 1ph input, or a 5hp rated using 3ph? I won't lie, if I can eliminate the RPC from the equation and still safely power the system, that would be the preferred outcome. I would appreciate any feedback to confirm that I'm on track and not being a misguided fool.
Thanks

Mark

Click to expand...

1. The VFD can slow things down but there will be no INCREASE in torque. The low speed on the motor doubles the torque. You may want to wire the VFD to the low speed and can best of both worlds.

2. Yep.

3. Most VFDs will need a break resistor only if you need to stop the motor VERY, VERY fast - less than on a dime. Test first and add complications only if really needed.

4. Sure.

5. Yep.

Run 220V directly to the VFD. That is what the VFD likes. Make sure your wiring/fuses etc can carry the current - some 20 to 50A usually.

Alex,
Thank you for the swift and thorough reply! It seems I actually have gained some understanding. If the VFD can be wired to utilize the function of the low speed wiring, I will gladly do that to maximize the full function of the lathe and I will have to see which models would offer that feature. Your last line makes me want to confirm that you mean I can input 1ph. That being the case and if what has been shared previously, I should purchase a VFD that is nominally in the 7.5-10HP range to offset the de-rating that many talk about. the motor is rated for. In high speed/5HP mode, the motor is rated for 13.4A, so well within the specs of even more lightly rated VFD's. I'm thinking VFD shopping will need to commence, but with a much better understanding of what to look for.
Thanks again

Mark

And then, there are “DC common bus” units...