Finally a way of using cheap 380v motors for DIY builds?

Like most of you guys, I have seen some of the tantalizingly cheap deals on awesome powerful and manly 380v industrial spindle motors and had to pass them up because there was no cost effective of powering them at home or in a small shop.

I bet I am not the only one who searched without joy or success for an affordable step up transformer to convert 220 to 380v or 460v. I only ever found devices that did the opposite this side of a $1,000.

I came across plenty of VFDs which converted 110v to 220v and allowed 1ph in with 3ph out and thought, why can't someone make one with 220v in and 380v out? The 380v devices use less amps so there was little difference anyway. But... there was nothing.... until today..... when I came across this:

https://www.ebay.com/itm/11KW-15HP-3...gcAAOSwdSRaF99

Could this be the answer? Can we finally starting digging in the grown-ups bargain bin?

Quote:

---

Originally Posted by Goemon

Like most of you guys, I have seen some of the tantalizingly cheap deals on awesome powerful and manly 380v industrial spindle motors and had to pass them up because there was no cost effective of powering them at home or in a small shop.

I bet I am not the only one who searched without joy or success for an affordable step up transformer to convert 220 to 380v or 460v. I only ever found devices that did the opposite this side of a $1,000.

I came across plenty of VFDs which converted 110v to 220v and allowed 1ph in with 3ph out and thought, why can't someone make one with 220v in and 380v out? The 380v devices use less amps so there was little difference anyway. But... there was nothing.... until today..... when I came across this:

https://www.ebay.com/itm/11KW-15HP-3...gcAAOSwdSRaF99

Could this be the answer? Can we finally starting digging in the grown-ups bargain bin?

---

There have been a few VFD Drives that you can do this with, this one you are looking at has a max output of 25amps, you input supply amps, will have to be much greater than this to be able to run it, just as 120v to 240v you need double the input amps to what ever the output motor size is, you have to also look at the Hz rating this has a max of 300Hz if that suits your spindles then you would be fine, that an expensive VFD Drive, most likely work out cost wise to use a 240v Drive and motor

If you live in NA the voltage is 120v / 240v for single phase

Quote:

---

Originally Posted by mactec54

There have been a few VFD Drives that you can do this with, this one you are looking at has a max output of 25amps, you input supply amps, will have to be much greater than this to be able to run it, just as 120v to 240v you need double the input amps to what ever the output motor size is, you have to also look at the Hz rating this has a max of 300Hz if that suits your spindles then you would be fine, that an expensive VFD Drive, most likely work out cost wise to use a 240v Drive and motor

If you live in NA the voltage is 120v / 240v for single phase

---

That 25a output will be for 380v. It should be enough to run anything that could be run safely on a 50amp 240v 1ph residential outlet.

That same vendor offers a 230v 1ph in to 230v 3ph output at 50amps. When my electrician was adding an extra 50amp 230v outlet for me last week, he said that was pretty much the limit in my area. He told me he had installed some 240v to 480v and 240 to 380v transformers for customers but they alll over $1500.

Have you seen other VFDs with 220v in and 380v out? I couldn't find any when I last looked.

I see the value of these things as having the flexibility to buy some of the 380v Colombo used spindles. You rarely ever see a good deal on a used 220v ATC spindle but used 380v spindles are worthless. Anyone that could use one would probably buy new gear.... until now...

Also, if you were building a mill, I have seen 380v 4 and 5hp 40 taper industrial CNC spindle heads for $500 to $1000. Obviously the preference is to buy 220v spindles but it sure would be nice to have more options...

if you buy more 400 volt capacitors, you can run a 480v vfd, such as early AB 1305 drives, on 240v single phase by connecting one line to all three of the three phase input at the terminal block, and the other to the center of the two (or 4, or 6, 8, etc) 400v capacitors (which are connected in series for 800 volts) this is the same method used for almost all power supplies that have a single switch to convert from 120 to 240v operation.. you can either de rate the vfd or buy more capacitors.

i have heard someone has been doing this modification and selling them on ebay, and i've done it myself with an older AB 1305 drive. if you have three phase i believe you can connect one phase to the midpoint of the capacitors and the other two phases to the terminal block and you will probably not have to derate the drive much.. but i don't have three phase to experiment with at the moment.

Quote:

---

Originally Posted by Goemon

That 25a output will be for 380v. It should be enough to run anything that could be run safely on a 50amp 240v 1ph residential outlet.

---

I almost misunderstood you there, and was about to tell you that you can't get 25 Amps 3 phase 380V from 240V 1 phase 50 Amps, but then I realized what you were saying. :)

Quote:

---

Originally Posted by Goemon

Have you seen other VFDs with 220v in and 380v out? I couldn't find any when I last looked.

---

Yep. Lots. Search for 220V to 380V VFD on Aliexpress. There are lots. Also the one you linked to is only 300 Hz.

Quote:

---

Originally Posted by Goemon

I see the value of these things as having the flexibility to buy some of the 380v Colombo used spindles. You rarely ever see a good deal on a used 220v ATC spindle but used 380v spindles are worthless. Anyone that could use one would probably buy new gear.... until now...

---

Some of those spindles have the option of being connected in Star or Delta, which means that you can rewire them to 220V by switching a few of the connections. Some don't.

The monster I have is 380V, but I plan to run it on 220V instead of limiting the Amps. I did a thread about it on practical machinist.

The Voltage / frequency is constant (straight line at an angle, ie: constant slope) up to a point, so at lower RPM's you are not operating at 380V. Depending on what the power vs speed curve is for the spindle, you would never even notice you were limited to 220V for a large part of the speed range.

I'd like one of those 220 / 240V to 380V VFD's but would still limit it to 220V output so I could get more amps, because I'd rather run it at normal amps and a lower voltage for part of the speed range. Truth is I'll buy something used and cheap most likely, still haven't bought one.

Quote:

---

Originally Posted by Eldon_Joh

if you buy more 400 volt capacitors, you can run a 480v vfd, such as early AB 1305 drives, on 240v single phase by connecting one line to all three of the three phase input at the terminal block, and the other to the center of the two (or 4, or 6, 8, etc) 400v capacitors (which are connected in series for 800 volts) this is the same method used for almost all power supplies that have a single switch to convert from 120 to 240v operation.. you can either de rate the vfd or buy more capacitors.

i have heard someone has been doing this modification and selling them on ebay, and i've done it myself with an older AB 1305 drive. if you have three phase i believe you can connect one phase to the midpoint of the capacitors and the other two phases to the terminal block and you will probably not have to derate the drive much.. but i don't have three phase to experiment with at the moment.

---

Not sure I understand what you're saying. But I'm interested to learn more. Do you know of any videos or step by step examples of this procedure?

What kind of output voltage range can you select on your 480V VFD? I assume you can enter any points on a V/f curve from 0-480? So at lower voltages the power draw from the outlet is less for the same amps.

For someone like myself, who wants to run at 220 / 240 V max output voltage from the VFD with 240V single phase input (so that I can keep the available output amps up) can I modify a 480V VFD to get what I want? I ask because I may be able to pick one up cheap, and that would help me out. I also plan on using the VFD to do the phase conversion, I understand that this means you have to overspec the input current for the VFD unless it specifically states it's a 1 to 3 phase VFD.

I'd appreciate any additional info you could provide on what you did.

Quote:

---

Originally Posted by NIC 77

What kind of output voltage range can you select on your 480V VFD? I assume you can enter any points on a V/f curve from 0-480? So at lower voltages the power draw from the outlet is less for the same amps.

For someone like myself, who wants to run at 220 / 240 V max output voltage from the VFD with 240V single phase input (so that I can keep the available output amps up) can I modify a 480V VFD to get what I want? I ask because I may be able to pick one up cheap, and that would help me out. I also plan on using the VFD to do the phase conversion, I understand that this means you have to overspec the input current for the VFD unless it specifically states it's a 1 to 3 phase VFD.

I'd appreciate any additional info you could provide on what you did.

---

i really don't know what you need a 480v vfd for if you only want 220-240v output.
what are you talking about when you say "so that i can keep the available output amps up"

anyhow the voltage doubler modification to the rectifier is easy, take the vfd apart and solder a wire to the circuit board where the two capacitors are in series. apply 240vac to that, and one or more of the input terminals. its literally this simple: https://www.elprocus.com/wp-content/...ge-Doubler.jpg


most any vfd can deliver whatever volts and whatever hertz you want out of it. yes you can progrogram a 480v vfd to deliver 220vac, but it won't be near as efficient, and you'll be blasting the motor with pwm at 700 volts, when you could use a 240v drive that would only send 350volt pulses to the motor.

Quote:

---

Originally Posted by Eldon_Joh

i really don't know what you need a 480v vfd for if you only want 220-240v output.

---

Because I can get one cheap. Wouldn't need one. Perhaps I misunderstood. I thought you were talking about using a 480V VFD (ie: it says 480 on the nameplate) with a 240V input. Or are you talking about converting a 240V VFD into 480V Output?

OK wait, I think I understand, you are saying you can use a 480V VFD (on the nameplate) with a 240V input, but that this is a bad idea if you want to limit the output to 220 or 240V via programming the V/f curve?

I don't really know how they work inside, I realize they convert to DC and then to AC 3 phase. From what I've seen many VFDs will say 380 - 480V input, 0 to Vin output. So what happens when you apply 240V input to one of these without doing the modification?

Quote:

---

Originally Posted by Eldon_Joh

what are you talking about when you say "so that i can keep the available output amps up"

---

I only have so many amps available to me at 240V single phase. Convert that to three phase, now less amps, bump up the voltage, still less amps. I'm saying that I'd rather have the current available at 220V output than the voltage up to 380V. I'm essentially derating the spindle because I don't have the power to drive an 11kW spindle. If you starve the amps available it won't work right, but if you limit the voltage it will be exactly the same for a good part of the V/f curve.

When you set the current output limit on the VFD, you get one value to input, is that correct? For example you can't say, when supplying 100 Volts on the V/f curve at a certain Hz, limit to 25 amps, and when supplying 380 Volts at a higher Hz on the V/f curve, limit to 10 amps? You get one value to input here? Limiting the output current on the VFD is my way to make sure I don't suck more juice than I have. Also with the lower voltage, the max amps I'll have is about what the motor would normally use at full power. Of course, I don't actually plan to push it that far, even derated.

Quote:

---

Originally Posted by Eldon_Joh

most any vfd can deliver whatever volts and whatever hertz you want out of it. yes you can progrogram a 480v vfd to deliver 220vac, but it won't be near as efficient,

---

OK, these are things I don't know. How much does the efficiency change?

Quote:

---

Originally Posted by Eldon_Joh

and you'll be blasting the motor with pwm at 700 volts, when you could use a 240v drive that would only send 350volt pulses to the motor.

---

I don't really understand this. The PWM is a momentary spike? How is this a problem for a spindle that is designed to be run at 380V? Is it an efficiency thing? Are you saying it might be damaged from doing this?

Thanks for helping me to understand this, it's appreciated.

I don't think any of these solutions would allow you to run more powerful equiptment than you have the breaker for. It's not about running a 40hp motor in your garage. It's about being able to take advantage of that deal on a nearly 3kw ATC spindle that someone is selling for $400 because it was needlessly a 380v model and nobody else can run it.

The (very bad) idea I had for running 480v motors at home was buying a bunch of electric car batteries. A VFD that outputs the correct voltage is a much better idea.

Quote:

---

Originally Posted by Goemon

I don't think any of these solutions would allow you to run more powerful equiptment than you have the breaker for.

---

Obviously you can not break the laws of physics. Unless you're batman. Then it may be possible, but only on full moon lit nights.

Quote:

---

Originally Posted by Goemon

It's not about running a 40hp motor in your garage. It's about being able to take advantage of that deal on a nearly 3kw ATC spindle that someone is selling for $400 because it was needlessly a 380v model and nobody else can run it.

---

$400 for a good used ATC spindle? Hmmm, tell me more.

Well, your 3kw spindle will most likely only be 3kw at full RPM.

Whereas my 11kw derated spindle will be capable of that somewhere at around, 3000 RPM. So yeah, there are advantages if I can get it working, particularly in using larger diameter bits to achieve better material removal rates. If I could have found one with less power for cheap, I would have bought a different one. What it's "about" depends on the person, application, and expectation.

I'm more interested in using it for quick changing bits as opposed to automatically changing bits.

Quote:

---

Originally Posted by NIC 77

Obviously you can not break the laws of physics. Unless you're batman. Then it may be possible, but only on full moon lit nights.



$400 for a good used ATC spindle? Hmmm, tell me more.

Well, your 3kw spindle will most likely only be 3kw at full RPM.

Whereas my 11kw derated spindle will be capable of that somewhere at around, 3000 RPM. So yeah, there are advantages if I can get it working, particularly in using larger diameter bits to achieve better material removal rates. If I could have found one with less power for cheap, I would have bought a different one. What it's "about" depends on the person, application, and expectation.

I'm more interested in using it for quick changing bits as opposed to automatically changing bits.

---

bumping the voltage from 240vac to 700 volts dc and then back down to 380volts ac doesn't, in theory, lose any power.

if you can rewire that spindle for 240vac (if its wye, change it to delta) it would be more efficient to use a 240v vfd to drive your spindle.

so go ahead, use your 480v drive to drive your spindle at the derated watts that you can safely pull from your 480v spindle.

for the voltage doubler modification i described, i would not exceed 40% of the drive's rating and i would pay attention to how hot the capacitors in the drive are getting. keep in mind you can buy more of them and add them to the drive. you can also buy a separate rectifier and run the vfd from the 700 volts dc directly. that way you can blow your capacitors up without causing the drive to fail. (keep in mind you need to pay attention to input amps going into the rectifier, not output amps of the vfd going to the motor) also the rms amps going into the drive are going to be about double what the vfd is actually pulling from the outlet. its the rms amps that heat up the capacitors, and blow your breaker.


if you can buy a 20KW 480v vfd, you can probably drive your spindle at the full 11KW if you add more capacitors. also the capacitors in the drive are probably old and may need replacing anyways.


so the problem with limiting the motor amps at the vfd, is the amps need to be proportional to the rpm. so at full rpm (say the motor is designed for 60hz, then at 60hz) to limit the motor to half the shaft hp, the amps would need to be maybe 60% of name plate amps.

however at lower rpms you can run full nameplate amps into the motor, up to about 40% of the motor's nominal rpm before you've exceeded an arbitrary derate of 50% assuming the vfd and the motor are the same "nominal" KVA/hp.

Quote:

---

Originally Posted by NIC 77

Obviously you can not break the laws of physics. Unless you're batman. Then it may be possible, but only on full moon lit nights.



$400 for a good used ATC spindle? Hmmm, tell me more.

Well, your 3kw spindle will most likely only be 3kw at full RPM.

Whereas my 11kw derated spindle will be capable of that somewhere at around, 3000 RPM. So yeah, there are advantages if I can get it working, particularly in using larger diameter bits to achieve better material removal rates. If I could have found one with less power for cheap, I would have bought a different one. What it's "about" depends on the person, application, and expectation.

I'm more interested in using it for quick changing bits as opposed to automatically changing bits.

---

I wasn't talking about a specific deal I had seen, just giving an example of what might peak someone's interest in using 480v or 380v kit. If I had seen a $400 ATC spindle, I wouldn't be telling anyone else about it until after I bought it...

I have seen some nice 5hp industrial CNC milling heads in those 4th and 5th axis heads for $500 to $1000 because they were 380v or 480v. Also, any of the good deals I have seen on used 2.2kw Colombo ATC spindles have been 380v or more.

You also get access to some of those high end Yaskawa and Mitsubishi constant power spindle motors. If you were building a mill, a hobby level user could end up with a nice 40 taper spindle and very nice Yaskawa 6000rpm motor for less than one of those Chinese milling heads.

Quote:

---

Originally Posted by Eldon_Joh

so the problem with limiting the motor amps at the vfd, is the amps need to be proportional to the rpm. so at full rpm (say the motor is designed for 60hz, then at 60hz) to limit the motor to half the shaft hp, the amps would need to be maybe 60% of name plate amps.

---

Thank you for your feedback to my questions.

I believe that it depends on the power vs speed graph for the motor, for example I went to the HSD website and pulled the spec sheet for two spindles at random:

http://www.hsdusa.com/bo/allegati/Fi...fnz4100919.pdf

http://www.hsdusa.com/bo/allegati/Fi...4100917_1_.pdf

You can see that the rated current, which is presented in table form at the bottom doesn't change much over the speed range, it's certainly not proportional to the RPM. Of course these spindles don't max out on power at max RPM and are not a straight angled line to max power at max RPM as some of the less expensive spindles are. So I'm just saying that it depends on what spindle you have.

Quote:

---

Originally Posted by Goemon

You also get access to some of those high end Yaskawa and Mitsubishi constant power spindle motors. If you were building a mill, a hobby level user could end up with a nice 40 taper spindle and very nice Yaskawa 6000rpm motor for less than one of those Chinese milling heads.

---

Yes, I've seen a few monster spindles with ATC for cheap as well. The thing you have to be careful of is some of those spindles have specific requirements, like lubrication systems, where even a new lube cartridge will cost more than you got the spindle for at surplus.

I should have said inversely proportional.

a better way of explaining it:

assuming your vfd and motor are rated the same, and you've derated the vfd 50%, you can run any three phase motor up to 40% of its rated rpm at full torque, that is full motor amps, before the vfd exceeds the arbitrary 50% derate on the rectifier side of the system.

or you can run the motor up to 100% of its rated rpm, at up to 50-60% of its nameplate torque, before you've exceeded your vfd's 50% derate. the reason for the 40% rpm limitation at full torque, is because at 40% speed and full torque, the motor is no longer 80% efficient, but more like 60%.


anyhow this is why i'm saying setting a current limit on the vfd output limits you on the low end severely, when there doesn't need to be any derate below 40% of nominal rpm.

Quote:

---

Originally Posted by NIC 77

Thank you for your feedback to my questions.

I believe that it depends on the power vs speed graph for the motor, for example I went to the HSD website and pulled the spec sheet for two spindles at random:

http://www.hsdusa.com/bo/allegati/Fi...fnz4100919.pdf

http://www.hsdusa.com/bo/allegati/Fi...4100917_1_.pdf

You can see that the rated current, which is presented in table form at the bottom doesn't change much over the speed range, it's certainly not proportional to the RPM. Of course these spindles don't max out on power at max RPM and are not a straight angled line to max power at max RPM as some of the less expensive spindles are. So I'm just saying that it depends on what spindle you have.



Yes, I've seen a few monster spindles with ATC for cheap as well. The thing you have to be careful of is some of those spindles have specific requirements, like lubrication systems, where even a new lube cartridge will cost more than you got the spindle for at surplus.

---

I didn't know that. I thought those high end 40 taper spindle cartridges were sealed and self contained units that required no additional cooling or lube while in use. There is always a catch....

I have seen some with space to run coolant through the toolholder but I thought that was like the regular coolant you spray while cutting. I'll make a mental note to ask about that before buying anything like that.

I guess there is a reason why people love those old Bridgeport mills. They have their faults but they are mostly plug in and play if you can figure out how to move one into your garage...