Can anyone help me with a running a 3-phase Juki at home?

[williaty]

13 hours ago, DrmCa said:

Are you certain that you are feeding 200-240 voltage? I do not mean to insult your intelligence but you did not mention whether you have a tester or not, and I do not know whether you are relying on the VFD's display.

I have a Fluke 87 V meter that I've been using to confirm the actual output. Unsurprisingly, the programmed value doesn't exactly match the measured output. I can turn it down to as low as 140V phase-to-phase and the SC-1 still gives the overvolt message.

[williaty]

Oh wow, lots of replies I've missed! I'll try to answer everyone's questions in a summary:

 

1) Yes, the fallback plan here is simply to strip the fancy functions off and power this with a $100 servo motor if there's no way to get the computer running.

2) I am aware of rotary phase converters but there's two major drawbacks. The cheapest ones I've found still cost way more than I paid for both machines put together. The rotaries also make continuous noise and this is for an in-residence business, not a factory so the noise matters.

3) I've been calling around to various Juki dealers and they've all said they either refuse to deal with automated machines at all or refuse to deal with 3-phase automated machines after prior bad experiences.

4) I've asked one shop what it'd cost to buy the current generation control box and motor to refit the machines and I'm still waiting on their quote. I suspect the answer will be more than I can afford though.

 

Part of the problem with both a new control box and with the rotary phase converters is cost. While I'd love to have some of the features the computerization offers (mostly needle-down which I can get from a cheap servo anyway, and the reverse button near the needle with the auto thread cutter a kinda-nice idea), the fact is that I'm not in a full production factory and I'm not too short of time in the day to get my work done. Sure, I'd love to save a little time per piece because who doesn't like more profit, but in reality I'm not going to make enough more money with a more efficient machine to pay off $1,000 in electronics (or less, I know used rotaries are a little less than that) in a timely manner.

[DrmCa]

Going out on a limb here, but does a VFD give out a pure sine wave or a bunch of sharp pulses? If the latter, then you may get away with routing the 3 phase through a transformer close to 1:1, to smooth the output back to the sine wave. The machine may not be fond of harmonic interference from the thyristors or PWMs inside the VFD, and that may be throwing E11.

By the way, is E11 supposed to be thrown for overvoltage only, or for undervoltage too?

[SARK9]

For what its worth, one of the larger sewing machines I have came with similar automated functions....a Mitsubishi Limi-Stop Z servo that was all 3 phase....it had the usual factory stuff...backtack, needle position, foot lift, reverse...the mechanical stuff was pneumatic but the actuator valves were controlled by the electronic brain on the main unit. What you may find interesting was it was powered by a *static phase converter*  and plugged into a typical household 220V outlet. The small HP requirements for your machines may make that reasonably economical compared to an actual roto-phase setup. The bonus is, no motor running the whole time you need the 3ph power. I've used one static phase converter in the past (came with a new Powermatic model 72 table saw I bought) and I never felt like it was underpowered when ripping long 2" Honduras Mahogany boards down to width. I use a couple of 5hp roto-phase motor conversions to power the machine tools my current shop, and you may find the droning of the motors a bit annoying if they are indoors with you.

-DC

Edited January 19, 2022 by SARK9
phantom letter

[williaty]

On 1/19/2022 at 6:26 PM, SARK9 said:

For what its worth, one of the larger sewing machines I have came with similar automated functions....a Mitsubishi Limi-Stop Z servo that was all 3 phase....it had the usual factory stuff...backtack, needle position, foot lift, reverse...the mechanical stuff was pneumatic but the actuator valves were controlled by the electronic brain on the main unit. What you may find interesting was it was powered by a *static phase converter*  and plugged into a typical household 220V outlet. The small HP requirements for your machines may make that reasonably economical compared to an actual roto-phase setup. The bonus is, no motor running the whole time you need the 3ph power. I've used one static phase converter in the past (came with a new Powermatic model 72 table saw I bought) and I never felt like it was underpowered when ripping long 2" Honduras Mahogany boards down to width. I use a couple of 5hp roto-phase motor conversions to power the machine tools my current shop, and you may find the droning of the motors a bit annoying if they are indoors with you.

-DC

hmm.. this has me curious. Static phase converters synthesize the 3rd phase to get the motor started and then drop it, right? So the motor runs off 2 out of 3 phases and that's why you see a power reduction when using a static converter. If I understand it correctly, I mean. I wonder if that'd work with this thing since it has "open phase" as one of it's error codes. I suspect it might see that phantom 3rd phase drop out and get pissed.

 

Regardless, I'm looking up prices to see if it's worth trying.

Edited January 21, 2022 by williaty

[Matt S]

2 minutes ago, williaty said:

hmm.. this has me curious. Static phase converters synthesize the 3rd phase to get the motor started and then drop it, right? So the motor runs of 2 out of 3 phases and that's why you see a power reduction on one. If I understand it correctly, I mean. I wonder if that'd work with this thing since it has "open phase" as one of it's error codes. I suspect it might see that phantom 3rd phase drop out and get pissed.

It might be that static converters are setup to run a little differently with our electrical grid over here, but as I understand it static converters make an ersatz third phase from the supplied one through a capacitor as you say. That makes this phase lag by roughly 90 degrees, which is "close enough" to the ideal 120 degrees to work okay under most circumstances with a slight loss of voltage and increased noise and vibration due to imbalance. This is the minimum it takes to run a 3ph motor on a 1ph supply and is sometimes called a Steinmetz circuit. It's possible to make a second ersatz phase by connecting a suitable inductor between the first and third, which will lag behind the third (or ahead of the first), which will help the motor to balance a little better and provide a little more power. As more or bigger motors are run simultaneously the closer to 120 each phase will be, and so the better balanced everything is. I ran my 4-motor Fortuna splitter off a static for a few years and you could hear the motors become more balanced as they kicked in in sequence. This is essentially the basis behind a rotary converter -- a big "dummy" motor with no load which is used as a triangular array of inductors with reactances that vary at the right speed all at 120 degrees from each other.

Sometimes static converters have a bank of capacitors which are switched in and out of circuit manually or automatically in order to regulate the voltage drop from L1 to L3 across varying loads, however there is always a "run" capacitor in-circuit when running. They will often though have a larger "start" capacitor to get the motor turning, which is only in-circuit for a few seconds before being switched out.

[williaty]

43 minutes ago, Matt S said:

It might be that static converters are setup to run a little differently with our electrical grid over here, but as I understand it static converters make an ersatz third phase from the supplied one through a capacitor as you say. That makes this phase lag by roughly 90 degrees, which is "close enough" to the ideal 120 degrees to work okay under most circumstances with a slight loss of voltage and increased noise and vibration due to imbalance. This is the minimum it takes to run a 3ph motor on a 1ph supply and is sometimes called a Steinmetz circuit. It's possible to make a second ersatz phase by connecting a suitable inductor between the first and third, which will lag behind the third (or ahead of the first), which will help the motor to balance a little better and provide a little more power. As more or bigger motors are run simultaneously the closer to 120 each phase will be, and so the better balanced everything is. I ran my 4-motor Fortuna splitter off a static for a few years and you could hear the motors become more balanced as they kicked in in sequence. This is essentially the basis behind a rotary converter -- a big "dummy" motor with no load which is used as a triangular array of inductors with reactances that vary at the right speed all at 120 degrees from each other.

Sometimes static converters have a bank of capacitors which are switched in and out of circuit manually or automatically in order to regulate the voltage drop from L1 to L3 across varying loads, however there is always a "run" capacitor in-circuit when running. They will often though have a larger "start" capacitor to get the motor turning, which is only in-circuit for a few seconds before being switched out.

I am fairly sure this is a place where the differences between how the US delivers electricity and how the EU does it probably makes a difference. In pretty much all single-family residences, we get something that gets called single phase even though that's a damned lie. Our connection to the grid is 2 hot legs, each carrying 120V AC relative to ground, 180 degrees out of phase, and a neutral return connected to the center tap of the transformer on the pole outside. So it's a 2 phase system even if Americans refuse to call it that. Our low-power appliances run off one of the 2 legs brought into the house, providing 120V AC between that phase and neutral. Our higher power appliances run off the difference between the 2 120V 180-degree out of phase legs, which of course is 240V. *Most* of our 240V appliances don't use a neutral return at all but a 4-wire connection (2 phases, neutral return, ground) to large appliances is becoming more common so that the low-voltage portions of the appliance can be run off one 120V phase referenced to neutral. Anyway.. that's a digression...

 

So I need to turn the 240V service I have (which is 2 120V phases 180* apart) into 3 phases separated by 120* and producing a phase-to-phase voltage of between 200V and 240V to make this control box happy.

[Matt S]

8 minutes ago, williaty said:

I am fairly sure this is a place where the differences between how the US delivers electricity and how the EU does it probably makes a difference. In pretty much all single-family residences, we get something that gets called single phase even though that's a damned lie. Our connection to the grid is 2 hot legs, each carrying 120V AC relative to ground, 180 degrees out of phase, and a neutral return connected to the center tap of the transformer on the pole outside. So it's a 2 phase system even if Americans refuse to call it that. Our low-power appliances run off one of the 2 legs brought into the house, providing 120V AC between that phase and neutral. Our higher power appliances run off the difference between the 2 120V 180-degree out of phase legs, which of course is 240V. *Most* of our 240V appliances don't use a neutral return at all but a 4-wire connection (2 phases, neutral return, ground) to large appliances is becoming more common so that the low-voltage portions of the appliance can be run off one 120V phase referenced to neutral. Anyway.. that's a digression...

Yes I think you may be right -- we have "full fat" single phase 240v (the European harmonised standard is 230v, but it's really 240v in the UK and 220v on the Continent and usually around 244-247 depending on loading conditions in my workshop) delivered as a minimum. Usually about 100A from a 25-35SQMM service cable (either direct buried or ducted), or 60A for small houses and flats. In reality it's a single phase from a 3ph generation and distribution infrastructure. It's not unusual to have 100A 240v 3ph service to normal houses and small commercial buildings, and I think will become quite common with the increases in electric vehicle charging, a general move away from gas and oil heating, and microgeneration that's expected. It's already common in mainland Europe. In fact we've got it at this house but only a single phase to the service cutout, as it would have cost a lot more in installation and internal wiring costs when we made alterations. It's significantly cheaper for me to run a converter when I occasionally need 3ph than it would be to wire for it. AFAIK we only get split-phase stuff as temporary supplies on building sites (110v, arranged as 55-0-55 centre tapped to ground).
 

Quote

So I need to turn the 240V service I have (which is 2 120V phases 180* apart) into 3 phases separated by 120* and producing a phase-to-phase voltage of between 200V and 240V to make this control box happy.

We're moving beyond my ken here, as for obvious reasons I only really know how to fanangle our setup. Have you considered a rotary in a "hush box" like for compressors, or maybe installed remotely in an outhouse?

[suncat33770]

Here is 3 phase setup I am using on my 3 phase Dayton grinder.  It works well for the few times I use it.  I really know nothing about how it works I just found it on the internet.....

3phase 1.pdf

[480volt]

Since I’m in the business, I notice when people start using electrical terminology incorrectly. What you get in US homes is single phase power, with the transformer winding between the two legs center-tapped to provide the neutral. As far as I know, actual two-phase power, which requires four wires, is used only in downtown Philadelphia, which has legacy buildings permanently wired that way. It’s supplied via Scott-T wired transformers, since no utility generates anything but three-phase. Look it up if you like, but you and I will never see one.
Three and four-wire description means something very specific in the electrical industry: three-wire indicates a panel or equipment operating on three-phase with no neutral, therefore a single voltage, typically 208 or 480. Four-wire indicates the presence of a neutral, therefor two voltages: typically, 120-208 or 277-480. The ground is never considered as part of the set of conductors.

But none of this has any bearing on the OPs question. The electronics on a piece of three-phase equipment will not be three-phase, and will typically have a transformer wired across two legs. If you’re going to use an RPC, you need to use the legs connected to the panel to feed the electronics. The derived third leg is not 120 degrees out of phase with the others, and this leads to odd, variable voltages when measuring against the other legs. You can correct the phase angle by adding capacitance, but since the correction varies with load, it might not be worth messing with. Three phase motors run just fine without any correction at all. Three phase motors are also reversible by swapping any two legs, so you would need to bump it to verify rotation, and still have the electronics on the correct legs. I really don’t like static converters as they are mainly a means to get a three phase motor running and don’t meaningfully supply the third phase. My own RPC is quiet compared to the tools it supplies, way quieter than my 111w-151 or ASE #9. The only balanced, true three phase source some one mentioned is a motor generator set, but that would be ridiculous just to get a sewing machine going. A VFD might work for the motor, but the electronics package is not going to like it. VFDs also control voltage and frequency by switching on and off rapidly, this produces a square wave not a sine wave, and motors rated for this are labeled “inverter duty”.

Anyway, if the motor is not integral to the accessories, probably easier and cheaper to just buy a single phase motor for it. Otherwise I’d try an RPC. Then you can power a mill, a lathe, big drill press…