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jhe.1973
02-23-2015, 11:03 PM
Hi Everyone,

Sometime back, I am quite sure that I have seen suggestions on this forum that VFDs are available to obtain 440 3PH from a 220 single phase input.

I have e-mailed three retailers and only had one reply that they don't handle any that will do this.

Can anyone shed some light on this? I have a friend that I am trying to help and so far, no luck in finding anything.

His requirement is only a 3/4 HP lathe so we're not talking much of a load.

Thanks in advance for any help!

JRouche
02-23-2015, 11:07 PM
Im thinking there will need to be a transformer prior to the VFD. JR

J Tiers
02-23-2015, 11:17 PM
Many 115V 1P input to 230V 3P output types, but I am not aware of one as you describe.

jhe.1973
02-23-2015, 11:32 PM
Im thinking there will need to be a transformer prior to the VFD. JR

That's what I am starting to think now also.

I saved the sites for 3 different suppliers back when I was looking for myself and thought one of them had a VFD that would do it.

Something about my memory not what it used to be perhaps - nah, I'm still young!

Yaah right!

:D

Tundra Twin Track
02-23-2015, 11:34 PM
I am sure SMVector Lenze AC Tech has VFD to convert to that voltage and made in USA.

becksmachine
02-23-2015, 11:43 PM
Im thinking there will need to be a transformer prior to the VFD. JR

How about a transformer before a RPC rather than a VFD? Or after a RPC?

Dave

sch
02-24-2015, 12:02 AM
An approximation, that is close enough to work, is available in the UK: http://stores.ebay.co.uk/drivesdirectinvertersltd_W0QQ_fsubZ5
Not cheap, but will do the job if a rotary can't be whomped up.

These are 240 1ph to 415v 3ph VFD at ratings well above the 3/4hp desired. I suspect the larger ones assume a 3ph input but didn't click on these.
I have never seen these in the US, but in Europe where 220-240v 1ph is the
standard power supply there is a small demand for these inverters to run 400-440V single voltage motors 3ph motors. This is analogous
to the 115 to 230V VFD sold in US.

PStechPaul
02-24-2015, 12:07 AM
For only 3/4 HP you can use a 500 VA (or larger) 220-220 transformer connected as an autotransformer to get the 440V. Most smaller VFDs will work on single phase (although often at reduced power) so you might need a 1.5 or 2 HP VFD. Another possibility is using capacitors and diodes to boost the 220 VAC to 600 VDC for the DC link. Here is a circuit and simulation results:

http://enginuitysystems.com/pix/240Sine-640DC_Doubler.png

Some capacitors that might be suitable:

http://www.ebay.com/itm/High-Voltage-PolyproMetallized-Film-Capacitor-220uF-600V-/231481845396?pt=LH_DefaultDomain_0&hash=item35e564a694

http://www.ebay.com/itm/Run-Capacitor-LOT-10-100-MFD-uf-370-440-v-vac-volts-Round-Electric-Motor-HVAC-/261104087753?pt=LH_DefaultDomain_0&hash=item3ccb0432c9

A transformer that should work:
http://www.ebay.com/itm/ACME-Transformer-T-2-53011-S-Transformer-1-5-KVA-1-phase-T253011S-/281592283536

sch
02-24-2015, 12:17 AM
Stepup transformer for 220->440V 1ph rated at 1kva feeding a 440v VFD would likely be the cheapest route, provided the VFD accepts 1ph input. Some will, but will be derated about 30-40% from their
3ph input rating. So for 3/4hp motor at least a 1hp VFD would be advised. Some 440v VFD will fault on 1ph input and refuse to work, need to look at the manual to check this. Most likely a
four winding (two primary/two secondary) transformer would work with the two primaries in parallel and the secondaries in series. Needless to say dealing with 440v at multi-ampere capacity
is a dicey thing to do if you are unfamiliar with the NEC.

jhe.1973
02-24-2015, 01:12 AM
As usual, thanks to ya'll so far for the great help!

Steve, I dug this transformer out as you must have been replying. I think this is what you are referring to:

http://bbs.homeshopmachinist.net/attachment.php?attachmentid=4258&d=1546028275

http://bbs.homeshopmachinist.net/attachment.php?attachmentid=4259&d=1546028334

So, will this transformer work? I am concerned about its age seeing as how it doesn't have a ZIP code in the address.

Here is the motor nameplate that I should have posted right away - was having lots of trouble w/Photobucket being SUPER slow!

http://bbs.homeshopmachinist.net/attachment.php?attachmentid=4260&d=1546028433

lakeside53
02-24-2015, 01:16 AM
You have to reverse connect it, and it's 208 not 240 on the input. It's also an auto transformer. Take great care....

That's a Dahlanger wound 2 speed motor. I has a similar motor on an Emco lathe. With a vfd just select the higher speed (which will be 1725 rpm +/- on 60hz), and use the vfd to slow it down (or speed up) No serious loss in performance over switching the two windings - you still have 0.2kw at 30hz - 850 rpm (instead of 0.27). If you connect it in the low speed config you'll have lousy torque at 120hz and not much more headroom to increase speed (if that's important).

The Artful Bodger
02-24-2015, 01:54 AM
Why the four windings?

I think there is a bit of confusion going on here, I am certainly confused.:confused:

jhe.1973
02-24-2015, 02:36 AM
You have to reverse connect it, and it's 208 not 240 on the input. It's also an auto transformer. Take great care....

That's a Dahlanger wound 2 speed motor. I has a similar motor on an Emco lathe. With a vfd just select the higher speed (which will be 1725 rpm +/- on 60hz), and use the vfd to slow it down (or speed up) No serious loss in performance over switching the two windings - you still have 0.2kw at 30hz - 850 rpm (instead of 0.27). If you connect it in the low speed config you'll have lousy torque at 120hz and not much more headroom to increase speed (if that's important).

Lousy torque is just what my friend was complaining about and he thought it was due to his running the lathe on 220V. I think he has a phase converter of some sort but I have to talk w/him more about his installation.

Trouble is he is 9 driving hours away so I can't just pop over.

He also says he thinks of electricity as a black art & doesn't know much about it.

I looked at the digital inverter that Steve supplied the link for, and I think that might be the simplest solution for him & whoever he has hook it all up. That is if they export to us in the colonies.

:D

metalmagpie
02-24-2015, 10:47 AM
Having to power 440V two speed motors is common. I went through that recently. What I did was to first make 240VAC three phase using an RPC, then used 3 single phase transformers to step the voltage up. There are other ways.
metalmagpie

sch
02-24-2015, 11:42 AM
jhe: the transformer you pictured is a 3 phase transformer which can be used as a 1 phase transformer, but inputting 220-230v into the secondary rated at 208 will result in
as much as 486v on the 440v side, which may be a bit much for your 415v motor. There are ways around this which I will omit for now. Your transformer has two iron
cores, so if used as a 1ph device, it will not handle the full 1kva rating, probably considerably less. So IMO, is marginal for what you need. I don't think it is an autoformer
but an ohm meter could verify that.

When I mentioned "four windings" I was thinking of common isolation types which have two primaries and two secondaries which are series or parallel connected to provide
120/240 on one side and 120/240 or 240/480 on the other. 1phase assumed.

Stuart Br
02-24-2015, 12:05 PM
There is a way you can use a 230V VFD on a 415V motor if you can tolerate reduced torque at higher frequencies.
This is done by setting the base frequency to 29Hz. I have been using this technique successfully with my Colchester Chipmaster for a number of years, with no issues with torque for hobby use.

Detail from a UK supplier on how to do this at https://www.inverterdrive.com/HowTo/240V-Supply-to-a-400V-AC-Motor/

lakeside53
02-24-2015, 12:50 PM
Lousy torque is just what my friend was complaining about and he thought it was due to his running the lathe on 220V. I think he has a phase converter of some sort but I have to talk w/him more about his installation.

Trouble is he is 9 driving hours away so I can't just pop over.

He also says he thinks of electricity as a black art & doesn't know much about it.

I looked at the digital inverter that Steve supplied the link for, and I think that might be the simplest solution for him & whoever he has hook it all up. That is if they export to us in the colonies.

:D

If he's using a Static phase converter to run single phase 240 to a 440 motor ? yep.. torque will suck. ;)

IF by chance he has a rotary converter, then he should just get a 3 phase step up transformer and have it wired with appropriate fusing by someone that knows what they are doing. 120v nibbes... 440 will kill you...

If you go VFD, it is not a general purpose phase/voltage converter... in general it needs to be wired directly to the motor and uses LV inputs for forward reverse, stop etc. Just dropping it on the input powers wires is not a solution.

If it was mine... I put on a single speed 3 phase 1hp 240v motor and an Hitachi (because I like them over many others) SJ200 VFD. Done.

jhe.1973
02-24-2015, 01:03 PM
I have sent inquiries to both of the U.K. suppliers that have been so graciously provided in this thread. I will let all know of the results as soon as I hear back.

Just a couple of months ago I set up my own 440V line for a couple of Hardinge lathes that I have had for 8+ years. :o

I used a 440/220V 3ph transformer (eBay) that I wired in reverse to the output of my shop built RPC.

I never bothered to balance the phases of the RPC for the last 30 or so years and have had no problems. The 440V lathe is working fine (seems to run OK) but I have open circuit voltage readings of:

Left leg to ground 289V

Right leg to ground 264V

Center leg to ground 270V

Between legs:

Left to center 492V

Right to center 445V

Left to right 505V

I made sure to take the 110V control transformer off of the 264V right leg to ground.

Does anyone see any problems with this setup? Is balancing the phases worth the effort?

RWO
02-24-2015, 01:04 PM
Your friend will save money and trouble if he chucks the bastard motor and buys a standard US spec motor and VFD. Fractional hp 3-phase motors are dirt cheap on Ebay as are the VFD's. He might need to alter the motor mount and replace the motor drive pulley, but those mods are not "black art".

RWO

RichR
02-24-2015, 01:06 PM
Hi Jim
I think voltage readings with a load on the RPC would be more meaningful.

lakeside53
02-24-2015, 01:20 PM
More importantly, DO NOT take rpc output or the transformer output measurement to ground or neutral. An RPC creates a VIRTUAL GROUND that is significantly different to your physical ground. for all intents, the output is DELTA. Measure across the phases only. it's get tricky though... Is your transformer delta or Y output? If Y did you ground the output Y point? If you did, then you can reference your derived neutral/ground - refer to the NEC though... this has to be done right.

The output measurements across the three phases aren't great and will affect the ability of your motor to deliver full load without overheating. You probably aren't using full hp though... and as was suggested above, most balancing isn't relevant unless done at target.

If your phase-phase voltages are unbalanced, you should derate the output. Nema recommends a max of 5%, and at 5%, the motor has to be derated to 75% of it's rated power. More reading : http://what-when-how.com/electric-motors/voltage-unbalance-electric-motor/

jhe.1973
02-24-2015, 02:39 PM
More importantly, DO NOT take rpc output or the transformer output measurement to ground or neutral. An RPC creates a VIRTUAL GROUND that is significantly different to your physical ground. for all intents, the output is DELTA. Measure across the phases only. it's get tricky though... Is your transformer delta or Y output? If Y did you ground the output Y point? If you did, then you can reference your derived neutral/ground - refer to the NEC though... this has to be done right.

The output measurements across the three phases aren't great and will affect the ability of your motor to deliver full load without overheating. You probably aren't using full hp though... and as was suggested above, most balancing isn't relevant unless done at target.

If your phase-phase voltages are unbalanced, you should derate the output. Nema recommends a max of 5%, and at 5%, the motor has to be derated to 75% of it's rated power. More reading : http://what-when-how.com/electric-motors/voltage-unbalance-electric-motor/

Here is the transformer as I set it up in a different enclosure. It came from a larger machine's electrical control cabinet:

http://bbs.homeshopmachinist.net/attachment.php?attachmentid=4261&d=1546028745

And here is a close up of the schematic/wiring diagram:

http://bbs.homeshopmachinist.net/attachment.php?attachmentid=4262&d=1546029028

I can't remember if I grounded the XO terminal as it shows! Does this help identify it as a delta or Y?


On edit: Duh, just looking at the 1st photo I can see that I don't have the XO terminal (far left) grounded. What is the effect of this? All machines & enclosures on system ARE grounded.

JRouche
02-24-2015, 07:22 PM
How about a transformer before a RPC rather than a VFD? Or after a RPC?

Dave

Thats what I have for my emco 120 cnc lathe. It has a 380v-3ph transformer. I feed it with an American Rotary 15hp RPC. Works real fine :) JR

lakeside53
02-24-2015, 07:56 PM
You are using this transformer reverse connected, but I doubt it's rated as such. Your "Input" (X side) is Y, but if you ground X0 from an rpc derived source it will mess things up because the pass-through mains power will see ground as source neutral, and that's 120v, so leave it alone.

Do you have a picture of the transformer wiring schematic without the wire covering the H side?

Doozer
02-24-2015, 09:34 PM
There is a way you can use a 230V VFD on a 415V motor if you can tolerate reduced torque at higher frequencies.
This is done by setting the base frequency to 29Hz. I have been using this technique successfully with my Colchester Chipmaster for a number of years, with no issues with torque for hobby use.

Detail from a UK supplier on how to do this at https://www.inverterdrive.com/HowTo/240V-Supply-to-a-400V-AC-Motor/

I quoted Stuart's post to make the comment that this is worth trying for a 440-480v only motor being supplied with a
230-240v VFD drive. By setting the base frequency to 30hz instead of the normal 60hz, the drive puts put the full
available voltage at the 30hz frequency (instead of at 60hz as it would normally be configured). This gives a 480v motor
all the low end torque up to half speed, and then it operates up to full speed with basically the same torque as had been
available at half speed. If torque has plateaued and speed continues to increace, that means horsepower available is about
half of nameplate rating.

So if your machine tool does not need to run maxed out (what HSM does?) than I suggest this simple VFD parameter
setting tip and maybe save the price of a transformer until at least try to run the VFD with the base speed setting
set to 30hz instead of the regular 60hz. It is not a cop out, it is just smart use of electrical knowledge. What you are
basically doing is giving the 480v only motor power, having the proper volts-to-hertz relationship, from zero up to half
speed. Since you only have available half the voltage that the motor wants, (and it happily takes this increasing voltage
up until half speed), then from half speed up to full speed, you an only give it that voltage. You can keep feeding it with
current at an increasing frequency until full RPM, but because your voltage has plateaued at half, torque will not rise in
proportion with the increasing RPM. This is OK for the motor, and up until half speed, it doesn't know anything fishy is
going on. By setting base frequency at 30hz, you are just changing the voltage output curve that the drive provides to
be at full available voltage by 30hz, rather than reaching the full 230v as the drive reaches the 60hz.

This scenario is exactly the same as running a 240v (connected) motor from a 240v VFD, with the drive outputting
120hz to the motor. Once the drive gets past 60hz, it has no more voltage available, but it keeps putting out current
at an increasing frequency, up to 120hz. The speed of the motor has doubled because the frequency it is being fed
has doubled, but without maintaining the volts-hz ratio (we can not feed it double the voltage, because we only have
240v) the torque can not also continue to rise. So we have a motor running at double speed, but we see no extra
horsepower from it.

To further aid in understanding this volts-to-hertz relationship for motors concept, consider the exact opposite scenario.
If you have 480v available, you can take a 480v VFD and feed a motor wired for 240v with it. In this case, set the base
frequency parameter in the VFD to be 120hz. That means the drive will have a volts-hz curve set to output the full
available 480v at 120hz, instead of the typical 60hz. So the motor (connected for 240v input) will see 240v with the
VFD outputting 60hz. Perfectly normal right? Now as you increase the frequency of the drive over 60hz, and on up to
120hz, the voltage increases also, past 240v and on and up to the fully available 480v when 120hz has been reached.
So the 240V (connected) motor is now running at 480v and 120hz. It is spinning at twice the nameplate rpm and has
twice the horsepower available. And it will run this way in it's normal temperature range.

If you keep in mind the volts-hz relationship and what voltage supply you have, and for what voltage you can connect
the motor you have, you can work out a power scheme that will deliver the torque and speed and power that your
machine requires. These above scenarios illustrate some of the ways that components can be connected to supply
a solution that might work for you.

--Doozer

Rich Carlstedt
02-25-2015, 12:50 AM
I took a 480/240 stepdown transformer -single phase and reversed it to a 240/480 stepup
Then I installed a 480 V Hitachi VFD and used single phase as the input and it works.
You need to de-rate the VFD and transformer
I used a 11 KVA trans, into a 10 KVA VFD to feed a 6.8 KVA motor on 480 V.
No need to do a RPC to 3 phase transformer to 3 phase VFD

Another way is to make a RPC and only feed 240 on one of each of the two windings of the 3 legs and pull 480 off the second winding.
In other words , the RPC becomes a RPC and a stepup transformer at the same time.
You should double the RPC size to do this so the current (s) don't overload the common winding.

Balancing a RPC using voltage readings is a false approach .
You must balance by amperage to justify equal work on each leg !

Rich

jhe.1973
02-25-2015, 03:20 AM
As the heading says, MANY thanks to all of you for taking the time & trouble to post such great advice!

First, I heard from my friend and here is his VFD:

http://bbs.homeshopmachinist.net/attachment.php?attachmentid=4263&d=1546029240

And here are the specifications:

http://bbs.homeshopmachinist.net/attachment.php?attachmentid=4264&d=1546029289

From the two suggestions about setting the base frequency it looks like he is all set to try that. If he needs more torque he can always go to a step-up transformer before his VFD.

So, I think his situation is covered.

Mine has gotten interesting.

I grounded the XO terminal and the OC voltage jumped up to 660, 580, 433 between the legs. When I started the lathe, it came down a bit to 517, 450, 414 on low speed and 552, 483, 420. But the fun really started when I started my 5hp air compressor and the lathe. I got one leg reading of 740 volts before the fuses blew.

Hmmmmmnnnn! Ya think Lakeside53 is on to something?


You are using this transformer reverse connected, but I doubt it's rated as such. Your "Input" (X side) is Y, but if you ground X0 from an rpc derived source it will mess things up because the pass-through mains power will see ground as source neutral, and that's 120v, so leave it alone.

Do you have a picture of the transformer wiring schematic without the wire covering the H side?

This does say something about making sure that circuits are properly protected I guess.

I have a picture now!

http://bbs.homeshopmachinist.net/attachment.php?attachmentid=4265&d=1546029511

Need less to say I have disconnected the ground and I came up w/another brilliant, but warped idea. ( I have an electronics guru friend that says that).

I have this already to hook back up as it once was when I was still moving in here and I had two 3ph systems:

http://bbs.homeshopmachinist.net/attachment.php?attachmentid=4266&d=1546029572

My bet is that this Roto-Phase will be more balanced than my idler motor system. I can easily dedicate this RPC to my 440V line and leave the rest of the shop wired to the system I have been using for ages.

I can let ya'll know how this all works out, but I probably can't get to it before tomorrow evening.

Any other ideas/suggestions will still be appreciated as everything has already been!

Hopefuldave
02-25-2015, 03:40 AM
As a dabbles in the Black Arts, I hacked a 415v-3-phase input VFD to fool it when fed from 240 single-phase, very simple IF you know.what you're doing...
It does mean derating the VFD though, so I used a 5hp VFD for my lathes 3hp, 3-speed, 415v motor - no problems so far...
This is easiest on older VFDs with 2 banks of reservoir capacitors as you can split the banks with the incoming neutral and turn it into a voltage-doubler, newer VFDs have higher-voltage caps in a single bank :-(

dian
02-25-2015, 04:37 AM
"The speed of the motor has doubled because the frequency it is being fed
has doubled, but without maintaining the volts-hz ratio (we can not feed it double the voltage, because we only have
240v) the torque can not also continue to rise. So we have a motor running at double speed, but we see no extra horsepower from it"

so if you double speed and hp stays the same, torque must have fallen by 50%. does it with the 230v not changing?

Doozer
02-25-2015, 08:42 AM
".....so if you double speed and hp stays the same, torque must have fallen by 50%.
I said that the motor will not have any more horsepower. Will it have less from torque falling off? I am not sure.
I do know when I run a motor heavily loaded up past 60hz, that it begins to slow down from the load, despite the
increased frequency I am feeding it, so I assume yes it is loosing torque. I have a small and heavily loaded motor
that actuates a Reeves drive on a lathe, and if I try to run it at 65hz, it begins to slow down and stall out. So there
must be torque loss when the frequency increases out of proportion with the voltage.


"....does it with the 230v not changing?

Not sure what you are asking here.

-D

Doozer
02-25-2015, 08:51 AM
...Another way is to make a RPC and only feed 240 on one of each of the two windings of the 3 legs and pull 480 off the second winding.
In other words , the RPC becomes a RPC and a stepup transformer at the same time....Rich

I have thought about this concept before, but I never could get the wiring correct in my head.
Does this work? Did you ever hook this up? Interested to know.

-D

lakeside53
02-25-2015, 02:37 PM
As the heading says, MANY thanks to all of you for taking the time & trouble to post such great advice!
My bet is that this Roto-Phase will be more balanced than my idler motor system. I can easily dedicate this RPC to my 440V line and leave the rest of the shop wired to the system I have been using for ages.

Your transformer is a typical Delta -> Y. You are using it in reverse and feeding it from the Delta output of an RPC. With care, this is fine.

More on "care" - make sure your meter leads and meter are 600vac rated, and are clean/undamaged. Wear rated gloves if you can. Probing around 600v circuits (remember, 480 rms is 678 peak...) with crappy equipment is a good way to get killed. Much better to turn off the power, attach meter leads, turn on the power for a reading, then off to disconnect.




I reverse feed a 15kva transformer from a Phase Perfect for my 480v distribution; pretty much the same as with an RPC. It's all done " to code", but... code doesn't allow more then 240v in an attached residential shop... so...

Rich Carlstedt
02-25-2015, 11:03 PM
I have thought about this concept before, but I never could get the wiring correct in my head.
Does this work? Did you ever hook this up? Interested to know.

-D

No Doozer, I have not tried it yet , but it is on my agenda.
Standard 3 phase motor has 9 leads. With a 12 lead motor its even easier.
Using a Y layout , I was told to put one leg of 240 into #4 &7
Second leg into #5&8, and then a Cap from 5/8 to the #6 and 9 Leads.
480 3 phase then should be available on #1, # 2 and #3
The three windings on 7 -9 have a internal connection on a 9 wire motor
Because of 480 volts, I would not recommend anyone do it that is not qualified and accustomed
to working with high voltages because it can hurt you...bad
Rich

metalmagpie
02-26-2015, 10:49 PM
Hmmmmmnnnn! Ya think Lakeside53 is on to something?


Here's a tip: when it comes to wiring or bearings, lakeside53 should always be regarded as a very knowledgeable expert.
metalmagpie

jhe.1973
03-04-2015, 12:30 AM
Hi Everyone,

First off, I must apologize for not being able to get back here before now. Just an hour or so after my last post I went down with the first round of explosive vomiting & diarrhea. It lasted for several days & I didn't get out to the shop 'till today!

So I haven't yet hooked up the Roto-Phase I showed.


Your transformer is a typical Delta -> Y. You are using it in reverse and feeding it from the Delta output of an RPC. With care, this is fine.

More on "care" - make sure your meter leads and meter are 600vac rated, and are clean/undamaged. Wear rated gloves if you can. Probing around 600v circuits (remember, 480 rms is 678 peak...) with crappy equipment is a good way to get killed. Much better to turn off the power, attach meter leads, turn on the power for a reading, then off to disconnect.


I reverse feed a 15kva transformer from a Phase Perfect for my 480v distribution; pretty much the same as with an RPC. It's all done " to code", but... code doesn't allow more then 240v in an attached residential shop... so...

lakeside53: Thanks for keeping up with this and for providing your information.

Because my 440 line will be eventually dedicated for 2 lathes, each w/a fairly complex electrical panel, I am going to get some rated gloves for troubleshooting in the future.

Thanks so much!

I have a question concerning your mention of the code & 440 in residential shop. Are you talking about a regional code, or the NEC?

My shop isn't attached, but my friend's might be.


Here's a tip: when it comes to wiring or bearings, lakeside53 should always be regarded as a very knowledgeable expert.
metalmagpie

And I might add. very easy to understand with great advice/experience!

Thanks, thanks, thanks!

;)

on edit: I have two older bakelite cased analog meters in great shape. A 'Simpson' that reads to 1000V and a 'Triplet' that reads to 6000V, so I'm covered.

lakeside53
03-04-2015, 12:41 AM
Max residential voltage : I believe it's the NEC, but your AHJ (local) gets the final word. In my case I was told a flat "no" if it was attached to a residence. I figured I could argue only the appliance used 480, and the source was 240, but dropped that idea when I considered other cans of worms that might open on inspection ;

Meters : check the leads/probes. If in doubt - chuck them out, and replace.

PStechPaul
03-04-2015, 01:25 AM
You can get an insulation resistance tester (or megger) for not too much, and it will check the integrity of the insulation of tansformers, motors, and other components. Many of them are only 500 or 1000 volts, but it's better to use 2500 VDC or higher (5000 volts is often used for 480 and 600 VRMS equipment). If you put the step-up transformer in the same enclosure as the VFD, then it might be considered as 300V equipment if 208 or 240 comes into it. And if your 440/480 volts is center tapped, the voltage to ground will still be under 300V.

tmarks11
03-05-2015, 08:25 AM
You could make things simpler and just buy a replacement 3/4 hp motor for <$100. Gets you away from dealing with super-lethal voltage and all that sort of thing

Note: be careful about the voltage rating of the wire you are using to hook up your transformer, RPC, VFD, etc, as some appliance wire is rated for 300V... specifically, the insulation is only rated to stop the flow of current at the lower voltage.


Your friend will save money and trouble if he chucks the bastard motor and buys a standard US spec motor and VFD. Fractional hp 3-phase motors are dirt cheap on Ebay as are the VFD's.
+++1.

Armilite
03-07-2015, 11:01 PM
These are on ebay for $152 Buy it now.

http://www.ebay.com/itm/3HP-460V-GE-3PHASE-VARIABLE-FREQUENCY-DRIVE-NEW-D7221-/360209254954?pt=LH_DefaultDomain_0&hash=item53de250a2a

jhe.1973
03-10-2015, 03:51 AM
Hi Everyone,

Just to bring ya'll up to date.

I finally got the Roto-Phase hooked up and it worked, but w/a big surprise.

When I start the lathe I get a huge amount of noise from control cabinet. It sounds like it is stripping gear teeth it is that bad.

Once the spindle is turning ( a second or two) the rattling stops and all seem OK.

But it won't start on high - just makes the terrible noise. Plus, even though the spindle isn't turning, the noise continues from the cabinet and I have to kill the power to it (stop button).

I am pretty sure that the noise is from the contactors jumping in and out of the circuit 'cuz the Roto-Phase isn't quite big enough for the entire load. I think the motor is drawing so much the contactors only get what is left over.

Here is a shot of the control cabinet for those who aren't familiar w/Hardinge machines:

http://bbs.homeshopmachinist.net/attachment.php?attachmentid=4267&d=1546029899

The 3 light brown things are the original contactors and I had to add the white face one 'cuz this is a later machine on an earlier base.

My plan is to run a separate 110V line into this cabinet and eliminate the control transformer in the lower right.

When I was piecing this machine together (from 3) I bypassed the transformer this way to check out all the control circuits and straighten out a lot of the improper wiring.

The Roto-Phase seems to run all 3 of the motors just fine, it just has trouble supplying the control circuits.

Anyhow, that's my next experiment!

lakeside53
03-10-2015, 12:17 PM
My guess is that you are trying to use the generated voltage leg (T3) for the Transformer... don't do that.

Unless you really know what you are doing... and even then not a good idea... don't just run a 120v to your system to bypass the control transformer. In addition to dropping the voltage, the control transformer also provides isolation to protect the user. Not sure why you need to remove it anyhow - 240 via t1/l1 and t2/l2 I available as pass though from the rotophase and not affected by the lathe startup.

Doozer
03-10-2015, 01:11 PM
An alternative point view...
I have a 6hp rotary phase converter in my shop that powers about 10 twist lock
outlets on the wall. I wire all my machines so the 3rd leg powers the control
circuit intentionally. That way, if my RPC is not turned on, the machine can't
start at all. Prevents sitting there and humming on 2 phases and not starting.

If your contactors are dropping out, perhaps you run caps are not balanced
properly for the load.

-Doozer

lakeside53
03-10-2015, 06:05 PM
If your contactors are dropping out, perhaps you run caps are not balanced
properly for the load.

-Doozer

Or the rpc just isn't big enough. A hard starting 5hp lathe like mine needed a 15hp idler to start up reliably in high gear. If not, it took way too long to spin up and badly sagged T3. On the same 15hp motor, my buddies 6hp Nardini won't start in high gear unless it's switched to low speed first, and even then... marginal.

I'd connect the transformer to T1/T2, and assuming that eliminates the control problem, do some measurements on T1-T3 and T2-T3 at start up. Balance as needed or get a bigger idler (or use a vfd for soft start).

If you have overloads on your lathe motors, inadvertent single phasing won't be a problem other than the need to reset them.

jhe.1973
03-10-2015, 08:26 PM
My guess is that you are trying to use the generated voltage leg (T3) for the Transformer... don't do that.


Thanks once again for the insight! Lathe/RPC/Transformer is working now just as it should. You were right about taking the control circuit off the generated phase. Reading your post jogged my memory that I was the one that had moved the transformer lead because I had a 660V OC reading w/my idler motor RPC. I did not like exceeding the 600V rating of the wire insulation used throughout the system.

Now the OC reading is 540V and it drops to 515 & 518 for low & high speed respectively.

I am pretty sure that the instructions that came with my first commercial static phase converter decades ago mentioned not to hook up any contactors to the generated phase. I remember the instructions specifically saying to check out which lead(s) on the machine would energize the contactor before applying power to the machine.

Seeing as how this transformer has a tap in each of the coils for 415V output, do you forsee a problem if I wired the leg that is producing the 515/518V to the 415V tap? This is just to get closer w/balancing the phases.

Spindle running readings are now:

Left to center 458 low speed 485 high

Right to center 428 low speed 463 high

Left to right 515 low speed 518 high

Thanks again for keeping up w/this & for the advice!

lakeside53
03-10-2015, 09:02 PM
I wouldn't mess with the transformer taps to try to fix the generated leg. The transformer (assuming it's not overloaded) is simply tracking the input voltages. You need to balance the rpc.

I'm a little confused... your voltage readings indicate that the low speed is drawing more power than the high speed. Can you confirm that again? 458 428 515 (low speed) is pretty horrible "balance", and that is at low load. Any way you can can get readings under a decent load? (yes, it's difficult). You can balance current also, but if you balance voltages motor current will follow anyhow.

Help me out : This thread started about your friend's motor, then switched to yours, and somewhere you mentioned 3 motors. What hp are you driving right now?

jhe.1973
03-10-2015, 10:06 PM
Help me out : This thread started about your friend's motor, then switched to yours, and somewhere you mentioned 3 motors. What hp are you driving right now?

Well will you look at that, at post #18 I hijacked my own thread. Busted!

OOPS! I can't read my own writing either. it is 458 408 515. Yeah it is correct & my mistake doesn't help either.

I have passed my suggestions (from all the input here & subsequent searches) on to my friend & haven't heard back yet.

Now my questions are all about my situation - yeah, it's all about meeeee! ;)

When I refer to the 3 motors, they are the spindle (.75/.38 HP, and coolant pump and vari-speed control motor (raises/lowers the c-shaft to change speed). All part of the original Hardinge design & all on the one lathe. The small motors are probably about 1/10 HP or so.

I will be happy to get some load readings, but one of the drive belts is shredding LOTS of rubber powder & fabric plys so I will have to wait until I can get decent belts installed. I was going to change the spindle bearings at the same time 'cuz these are quite noisy. I have what looks to be a good set of bearings, but if I can swing it for new I'd just as soon do that. Trouble is ABEC grade 7 bearings are SUPER expensive.

All this is to warn ya that I might not be able to get back here right away. Just having the machine running and useable (sort of) is a big help.

lakeside53
03-10-2015, 11:05 PM
What's the minimum and max HP listed on the the rotophase? I can't quite read the nameplate in your pic.

jhe.1973
03-10-2015, 11:55 PM
Sorry that I couldn't get any better view of the nameplate. The corrosion is pretty bad, even up close.

The largest motor HP is 1 and Max System HP is 3.

No load amps is 1 and there is no other amp spec.

I should also mention that I have maintained the center leg (white) throughout my wiring as my manufactured phase so I can readily recognize it at any machine I am working with the 3ph. So all my references to left & right legs are always the hot leads of red & black.

There is only one capacitor on the Roto-Phase and I am pretty sure that it has no marking/rating

lakeside53
03-11-2015, 01:29 AM
Should be fine. Tough to tune well for a two speed motor with one set of caps. Measure the output of the rpc (input to the transformer) and let us know. The transformer might be messing with the tuning, but that should settle down under load. I think you are going to have to mess with the rotophase, but you might have to call them. The three I've been into don't have start capacitor etc, and just two run caps.

jhe.1973
03-11-2015, 01:46 AM
Just ran out to the shop. Roto-Phase output:

Left to center 247

Right to center 280

Left to right 248

Plus, while there I checked & the coolant pump is a 1/10hp & the speed control motor is 1/20hp

I suspect that the one cap w/the Roto-Phase is only a run cap.

lakeside53
03-11-2015, 09:44 AM
The balance caps will need to be adjusted to bring down your generated leg. I suspect the rpc being so small is simply set high lightly loaded so it's "within some spec" when loaded. Your loads are fairly small. Any variances in output are multiplied by the transformer.

Running your motor unbalanced means you should derate it (by applied load), so catch 22.

jhe.1973
03-11-2015, 12:14 PM
I'll be contacting Arco Electric to get their suggestions, but it will have to wait until next week. I have a presentation this weekend that I am preparing for now and have to concentrate on that.

Given the type of work that I will be doing on this lathe, I doubt that I will ever come even close to a .75 hp load. I am more concerned as to whether or not the unbalanced phases will affect surface finish, and this remains to be seen.

Thanks for all the help and I'll be posting again when I have some more news.

;)

jhe.1973
12-28-2018, 04:40 PM
I'll be contacting Arco Electric to get their suggestions, but it will have to wait until next week.........................
Thanks for all the help and I'll be posting again when I have some more news.

;)

..............wait until next week..................what a joke! Next week came 3 plus years later..............

I just got off the phone with Arco Electric and the good news is that the unbalanced readings I am experiencing are typical for an unloaded motor. The tech I talked with said that as the motor reaches the rated load of the RPC, the phases should balance out pretty well.

Seeing as how I am unlikely to ever approach the rated motor load and have not noticed any problems since installing the new bearings I found, I've just been living with the unbalance.

Last year I obtained a jig bore that has two motors that are 440 volt only and I wanted to get this unbalanced 3ph thing sorted before I hook that machine up...........................in my spare time!

http://bbs.homeshopmachinist.net/attachment.php?attachmentid=1149&d=1492446566

Mike Burch
12-30-2018, 03:38 AM
I've not read every response to your original post—life's too short—so forgive me if this has already been suggested.

AliExpress have VFDs in great numbers, many with 220v single-phase inputs and 3-phase outputs. Indeed, I have bought two myself, though they are 230v output. If you search AliExpress long enough, you should find one that will do your job perfectly.