VFD for 120V-1Ph in to 125V 3-Phase Motor? [AEG from an Emco Super 11]

Hi everybody,

I have a newly acquired Emco Super 11 with an AEG motor running on household (single phase) 120V. The motor is actually a 115V 3-Phase unit using a capacitor to run off the single phase input. I'm planning to convert to VFD eventually so I'm wondering -- has anybody has done that?

It seems a VFD with 120V/1Phase-in to 120V/3-Phase-out is a bit of an oddball. I can't find one specifically rated for 110-120V 3-phase output.
Also, I'm a bit confused on this point since the catalog entries only specify input voltage. e.g. CFW300A06P0S1NB20 | Weg | AC Drives -- why is that?

A couple other questions:
The original gang switch flips the motor from Delta-connection (slow speed) to Y configuration (Dahlander for high-speed). Which configuration do you use with a VFD? -- Delta?.
Could you run that on 220V 3-Phase output given the Delta-configuration has the windings in series and the VFD is current limited?

Thanks ahead of time.

-Dave

A motor like that is so rare and oddball that nobody would bother making a VFD for it.

However you COULD just program a 230V VFD to only put out 115V at the proper Hz, in this case 60Hz. Any VFD I have worked on is capable of that, it just may take some time to read how to do it in whatever they would call something like the "Custom V/Hz pattern" chapter of the manual.

Why does this three phase motor have what appears to be a starting capacitor listed on the nameplate?

Jraef said:

A motor like that is so rare and oddball that nobody would bother making a VFD for it.

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Weg surely did. For-real, not as a listing mis-print. I had one. Galco had done a close-out at silly-low pricing. At 1 or 2 HP, the target market may have been sumthin' else, though. Industrial sewing machines, mayhap?

My "plan" for it was to be able to do a qick and dirty "test" of used 3-Phase motors off an ignorant 120 V extension cord where 3-P wasn't "remotely" in-reach.

Didn't have to fully power-up motors above its lowly pay-grade. Just show if a very slow, slow-ramp indicated they had all their windings still in decent order.

Only 3-P motors I've bought since were brand-new, and/or under Warranty, so that part didn't get much use before it was pitched in the bin with the other VFD's.

Wiser move for the OP, though is probably to either run it as-is, ELSE change the motor to something a tad more SANE if not also more powerful, concurrent with a decision as to whether RPC or VFD (or even Dee Cee?) makes more sense.. for HIS needs and use pattern.

Not sure but I suspect it's the same motor (or a small variant of the one) used for 3-phase applications in EU markets -- just badged to indicate it's legit for single-phase input. Caps are 2x100 Bosch motor capacitors in parallel. I sent an email to AEG and Emco for additional info but I'm not holding my breath I'll get anything back.

-D

Yes, somebody on the Emco group also suggested that. I will probably go that route -- there are 120V input VFDs but to your point, they don't seem to have any extra bells and whistles (i.e. braking ).

bigwave said:

Yes, somebody on the Emco group also suggested that. I will probably go that route -- there are 120V input VFDs but to your point, they don't seem to have any extra bells and whistles (i.e. braking ).

Click to expand...

VFD's don't brake for shit in small sizes with austere capacitor banks, regardless.

Absent external resistors or costlier beach-sand to route the power off-VFD to a local-area "pooled" DC bus, they simply don't have the resources for it.

"4Q" DC Drive by comparison can pass its full rated power-in rating back OUT to the "local" grid. No local capacitors in the game atall.

Might piss-off yer next-door neighbours, same shared pole or vault pig, but they surely can brake well!

'minds me of my ex. All teared up coming out of a high-end ladies shoe store as specialized in hard-to-find sizes.

"Nobody has 4 1/2 - 5 extra wides. I have feet like a DUCK!"

"Yah well. You sure do SWIM good!"

"And maybe NOW we know why yer Dad was State swimming champ?"

Jraef said:

A motor like that is so rare and oddball that nobody would bother making a VFD for it.

However you COULD just program a 230V VFD to only put out 115V at the proper Hz, in this case 60Hz. Any VFD I have worked on is capable of that, it just may take some time to read how to do it in whatever they would call something like the "Custom V/Hz pattern" chapter of the manual.

Click to expand...

Wolf has several 120V input VFDs. As long as you can pull off Jraef's suggestion it should be doable.

AC Drives | Variable Frequency Drives | VFD | Inverter

I know the WJ200 has the external brake resistor option as I have a couple of them. Some of the others probably do as well.

WJ200-007MF | Hitachi Drives | AC Drives

One might think the Wye connection was the one to use, but it might not be.

If you use the delta connection, the slower speed one, that will be 1700 RPM at 125V and 1 HP. You will be setting your VFD up to provide 120V RMS at 60Hz, even though the actual VFD is a 230V unit.

So, when set up like that, if you then crank the VFD up to full voltage, it will provide 120Hz, and run the motor at 3400 RPM. The thing is, it will also be 2HP at that speed!

You are not changing the stress on the motor, because of several things. First, the "volts/Hz" is the same, 120V and 60 Hz, so 2V/Hz, and 230V and 120Hz, still 2 V/Hz. Motor current will be the same, voltage double, so power also double.

Second, the motor, even if you limited the VFD to 120V RMS all the time, would be still getting voltage pulses corresponding to the 230V input, so there is no advantage to limiting the voltage.

The advantage you get with this suggestion is that you get better low speed power, you get the full range of speeds, and you also get better high speed power.

There is no downside, so long as the motor really is a 230V design. And either way you are assuming that, since the VFD, with the 230V input, is going to produce pulses that correspond to 230V, no matter what "RMS voltage limit" you program it to.

ptsmith said:

Wolf has several 120V input VFDs.

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Not uncommon, and limiting can work, yes.

But the Weg I cited was NOT a "doubler".

120 (and a bit) in, single-phase. 1 HP @ 120 (and a bit) out 3-Phase.

120 (and a bit) in, 3-phase, 2 HP @ 120 (and a bit) out 3-Phase.

No 220/240 output at all.

thermite said:

"4Q" DC Drive by comparison can pass its full rated power-in rating back OUT to the "local" grid. No local capacitors in the game atall.

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cool controller..but dang those DC motors are $$$$..I think i'm in the 'junior league' category with my little lathe ;-)

-D

bigwave said:

cool controller..but dang those DC motors are $$$$..I think i'm in the 'junior league' category with my little lathe ;-)

-D

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NEW Dee Cee motors can be outrageously costly in the "right type" of design and construction for heavy machine-tool use, variable-speed. "Type T" is the one.

USED? Not bad atall. I snatched-up FIVE in one go off a go-fetch to ERC in Ohio. All of them Reliance. All 180 VDC wound - the ones that are most easily run off 240 VAC single-phase input controllers that are limited by physics to 180 VDC output.

Also the only windings - 180 and below - that Reliance themselves approve for use without a ripple-filter inductor in series.

These are not permanent-magnet treadmill-class goods. So they are physically large. And dreadfully HEAVY.

TANSTAAFL

On the other hand? Treadmill-class goods have actually worked a right treat for several among us on BirdPort size mills and small lathes of similar needs, so...
not 'optimal'. But neither is it all that costly or risky.

JST said:

One might think the Wye connection was the one to use, but it might not be.

If you use the delta connection, the slower speed one, that will be 1700 RPM at 125V and 1 HP. You will be setting your VFD up to provide 120V RMS at 60Hz, even though the actual VFD is a 230V unit.

So, when set up like that, if you then crank the VFD up to full voltage, it will provide 120Hz, and run the motor at 3400 RPM. The thing is, it will also be 2HP at that speed!

You are not changing the stress on the motor, because of several things. First, the "volts/Hz" is the same, 120V and 60 Hz, so 2V/Hz, and 230V and 120Hz, still 2 V/Hz. Motor current will be the same, voltage double, so power also double.

Second, the motor, even if you limited the VFD to 120V RMS all the time, would be still getting voltage pulses corresponding to the 230V input, so there is no advantage to limiting the voltage.

The advantage you get with this suggestion is that you get better low speed power, you get the full range of speeds, and you also get better high speed power.

There is no downside, so long as the motor really is a 230V design. And either way you are assuming that, since the VFD, with the 230V input, is going to produce pulses that correspond to 230V, no matter what "RMS voltage limit" you program it to.

Click to expand...

Interesting.. It seems the main deal for not frying the motor is overcurrent protection for the field windings -- I'm not sure it's 220 inside but another S11 user is running his VFD just like that with no issues. When I get some time, i'll pop the cap off the motor to check the wire gauge. The lathe's gearbox is 2-speed so to max out the speed without changing pulleys or something, I need to get the motor up to 3400 RPM. Having never used a VFD before, I'm not sure what controls they have for current limiting. Bigger concern would be insulation breakdown at higher voltage-- also seems unlikely at modestly higher voltage (any magnet wire/motor experts out there?)

-D

I talked with Wolf Automation and none of theirs are 120'ish out. To your point, I have seen some no-name brands on Aliexpress but not going that route. I only found WEG units with 110 in, 230V out. I found a couple Allen Bradley units that were 110/110, 3P out at 1.5 HP. That would be the only true plug and play but they're spendy and limited to 1.5HP. I'm inclined to try the 230/230 route with current limiting.

-D

PS: ..shout out to Glen at Wolf Automation for great info. I will buy my inverter from them when the time comes.

bigwave said:

..... The lathe's gearbox is 2-speed so to max out the speed without changing pulleys or something, I need to get the motor up to 3400 RPM. ..........

-D

Click to expand...

The suggested system, going up to 230V at 120 HZ will do your 3400 rpm and deliver about 2 HP from that motor at 3400 rpm, when set up for 1700 rpm at 60 Hz and 120V.

Current limits are easily set on most any VFD.

As for the voltage, the wire is not the main issue. Turn-to-turn voltage is not huge, and the varnish on "magnet wire" is not a great insulator, but it does not have to be. The heavy insulation is between coils, and between phase windings, which is where the high voltage is. Having the motor dip-varnished also adds insulating material and improves reliability. Most older motors were made with coils tied, and dip varnished.

JST said:

The suggested system, going up to 230V at 120 HZ will do your 3400 rpm and deliver about 2 HP from that motor at 3400 rpm, when set up for 1700 rpm at 60 Hz and 120V.

Current limits are easily set on most any VFD.

As for the voltage, the wire is not the main issue. Turn-to-turn voltage is not huge, and the varnish on "magnet wire" is not a great insulator, but it does not have to be. The heavy insulation is between coils, and between phase windings, which is where the high voltage is. Having the motor dip-varnished also adds insulating material and improves reliability. Most older motors were made with coils tied, and dip varnished.

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I was actually thinking about doing the opposite and using the double-Wye [Dahlander-config] since those windings would normally see 120 in Delta config but with 240 on the input's (assuming that's the VFD out voltage) I'll get ~140 across any single coil which is not to much of a stretch from the nominal 120V input the the coils are designed to handle. Current spec for the Dahlander at 115V is 15.7A. I figure I can fiddle with current limiting to keep things from getting hot. I think i can adjust the VFD output voltage down a bit as well.

-D

It is no matter.

AS long as you use a 230V VFD, the pulse voltages will be equal to the 230V peak pulse voltage. Even if you turn the voltage down, the pulse width becomes narrower, but the basic pulse amplitude remains at between perhaps 310V and around 340V, depending on your mains voltage. Any spike voltages will be higher.

You might as well go for it.

bigwave said:

I was actually thinking about doing the opposite and using the double-Wye [Dahlander-config] since those windings would normally see 120 in Delta config but with 240 on the input's (assuming that's the VFD out voltage) I'll get ~140 across any single coil which is not to much of a stretch from the nominal 120V input the the coils are designed to handle. Current spec for the Dahlander at 115V is 15.7A. I figure I can fiddle with current limiting to keep things from getting hot. I think i can adjust the VFD output voltage down a bit as well.

-D

Click to expand...

Your windings won't be bothered by 230 VAC instead of 115 VAC so long as the HEAT from total energy under the curve is within bounds - which a(ny) sanely configured VFD can easily assure. You seem to have that need covered well-enough by this point.

I'd still call it a wise precaution to insert a dv/dt filter to insure any spikes are tamed 'coz those CAN be harmful.

Those "reactors" are surely cheap enough, and you need but a very modest one for the very tiny ration of power you are dealing with.

My TCI Sine-Gard to protect a whole load center and all the loads as "might, some day, maybe" be on it is 60 A rated, good for what? Easily 20 or 30 HP, load side?

It cost all of $79 used-but-good off ebay. The Copper in it isn't trivial!

There are whole tribes and nations of less aggressive ones out there, some silly high priced, others more realistically so, ergo CHEAP INSURANCE for an odd old motor you'd rather not have at risk.

You've done the right thing, caution-wise research. Now implement it.

"Wire and forget" errng on the side of caution is a righteous goal for those who basically just want to USE the machinery, going forward. Not re-invent it.

What size amperage wise would a dv/dt filter for that motor need to be?

Probably too big, which is apparently not a good thing, but cheap enough: Trans-Coil Inc TCI Line Reactor / Filter KLC8B 600V 8A KLR8BTB Sine Guard | eBay

ptsmith said:

What size amperage wise would a dv/dt filter for that motor need to be?

Probably too big, which is apparently not a good thing, but cheap enough: Trans-Coil Inc TCI Line Reactor / Filter KLC8B 600V 8A KLR8BTB Sine Guard | eBay

Click to expand...

That one's 8A rated. Here's a 4A at about half the price, free shipping;

Trans-Coil Inc TCI Line Reactor / Filter KLC8B 600V 8A KLR8BTB Sine Guard | eBay

The calculations are "out there" as part of selection & sizing guidance on the websites of "the usual suspects" who deal in new goods, TCI included and "not only".

BEST info source is right in the "heavy" or full technical published .pdf - not the "lightweight" basic brochure - for any given VFD.

Most maker's include a sizing table - line AND/OR load reactors - right there with all the rest of the info.

Typically, dv/dt are sized @ 3% for basic goodness needs, a more agressive 5%, more challenging situations. "Sine wave" claimed goods are generally more aggressive, yet.

And yazz- there is "insertion loss".

Which isn't necessaiy a "bad thing" atall where your utility mains are already running hotter than they were many years ago and/or yer VFD is MORE than capable vs the modest load.

My case, I'm right about where I "should" use "buck" transformers so the output of the Phase-Perfect isn't as aggressive.

My choice of nearly double the dv/dt inductance I theoretically need in choosing the bargain TCI does that cheaper as a byproduct of filtering than what I'd have to spend on Buck/Boost transformer(s) otherwise.

Other stuff on my plate but most of the parts are here already, so "soon" I'll have actual figures:

245/246 VAC utility mains for single-phase in

-> twin chokes, one per leg
-> Phase-Perfect
-> 3-P TCI Sine-guard

-> Square-D 3-P transfer switch (RPC array is the other source choice)

-> 27 KVA EGS-Hevi-Duty 1:1 Delta-in, Wye-out Drive Isolation Transformer.
-> Square-D "QO" 32-pos 3-P load center.
-> 5-Wire Hubbell outlets.

I "expect to be" right close to 220 VAC 3-P Wye (and not "208"..) and ...

...have NO hassles with my houseful of electronics. Which is FAR,FAR, more important to me than protecting Old Iron's Old Motors, not even RUN anywhere near as often as the 'puters, routers, and all manner of appliances, some with VFD's built-in, etc.

A Corcom O/E RFI/EMI filter will be added, service source side of that pair of heavy chokes, "if need be".

We'll wait and see what the Rigol 'scope reveals.

Whereas when wired as autotransformers, as is the usual case, buck/boost are essentially as "transparent" to transients as a Copper wire...

Read "useless" at blocking electrical noise and nastiness, most types we care about.

Naturally the "Dinosaur Current" side of the shop prefers full-isolation boost transformers, plus Corcoms, 'coz SCR DC Drives are nastier switchers than Vee Eff Dee - just at lower pulse-rates.

"YMMV"