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Old 03-05-2013, 02:36 PM   #1 (permalink)
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VFD as phase converter

I Asked about a Rotary Phase converter here Phase converter - Pirate4x4.Com : 4x4 and Off-Road Forum
And some of yall said go with a VFD.

SO, lets talk VFDs.

I have a lathe with a 10HP / 3phase /208-230-460V Motor (World Motors model # T779A ID# T779-B06-6437-M)

The current setup is wired to 3 phase/ 460 power using a Sumitomo AF-500 inverter.

It has become necessary to change the voltage to 208/230 1 Phase.

SO, I need an inverter sized so it can function as a phase converter at the 208/230 voltage.

SO Can I size the VFD for 10HP?

I think I read somewhere that if you are using it as a phase converter you have to de-rate it by HALF, which means I have to get a 20 HP VFD?
I asked a Drive guy about it and he said I cant feed the drive Single phase PERIOD.

What do I need and what size?
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Old 03-05-2013, 02:49 PM   #2 (permalink)
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VFD as phase converter

Yea you can. I have a 5hp 3-phase 230v fountain running off 230v single with a VFD running it.

You might try calling a local pump company. They will be able to give you more info on this.
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Old 03-05-2013, 02:57 PM   #3 (permalink)
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With an RPC you derate the motor making the 3rd leg 1/3rd (i.e. 5hp 3ph motor is only capable of creating a little more than 3hp in 3ph off single phase power).

Using a static phase converter you derate the drive motor 1/3rd as you're only driving it on 2 windings.

With a VFD, look at the manufacturers specs. Some require derating, some don't.

10hp is a lot, 746w per hp so you need basically 34a of 220v power (746*10/220) at peak. IIRC when looking into VFD's most manufacturers only go up to 5hp on single phase input, but 15hp units exist.

In any case, yes, doable with a VFD, just get a big enough one.
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Old 03-05-2013, 03:03 PM   #4 (permalink)
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Yea you can. I have a 5hp 3-phase 230v fountain running off 230v single with a VFD running it.

You might try calling a local pump company. They will be able to give you more info on this.
What size is the VFD rated?

Is it a 10 HP VFD? Is there anything special about the VFD?
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Old 03-05-2013, 03:16 PM   #5 (permalink)
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With an RPC you derate the motor making the 3rd leg 1/3rd (i.e. 5hp 3ph motor is only capable of creating a little more than 3hp in 3ph off single phase power).

Using a static phase converter you derate the drive motor 1/3rd as you're only driving it on 2 windings.

With a VFD, look at the manufacturers specs. Some require derating, some don't.

10hp is a lot, 746w per hp so you need basically 34a of 220v power (746*10/220) at peak. IIRC when looking into VFD's most manufacturers only go up to 5hp on single phase input, but 15hp units exist.

In any case, yes, doable with a VFD, just get a big enough one.
SO,

This VFD won't work, because it doesn't show a Single phase input?DURApulse - GS3 Drive Units (230 / 460 VAC SLV) Overview
Am I interpretting his right?
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Old 03-05-2013, 03:46 PM   #6 (permalink)
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SO,

This VFD won't work, because it doesn't show a Single phase input?DURApulse - GS3 Drive Units (230 / 460 VAC SLV) Overview
Am I interpretting his right?
Those do have single phase input, but only up to 3hp.

The Hitachi unit I've seen before has a dead link now, hrm. In any case, IIRC, new it was ~$1200. It makes building a 15hp RPC alot more palletable

EDIT: http://www.driveswarehouse.com/p-2125-pc1-100.aspx

There's an option.
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Old 03-05-2013, 04:02 PM   #7 (permalink)
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Those do have single phase input, but only up to 3hp.

The Hitachi unit I've seen before has a dead link now, hrm. In any case, IIRC, new it was ~$1200. It makes building a 15hp RPC alot more palletable

EDIT: PC1-100

There's an option.
I put together a 5 HP Rotary, and am on the look out for a 15 HP motor, but that still leaves me with a VFD Issue.

Who ever had this lathe, ripped out all the controls and went with the VFD, SO ....


with a rotary converter and a transformer, I could use the VFD that is on it, I guess.

It originally had a super sweet vacuum tube control scheme, but that is LONG gone.
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Old 03-05-2013, 05:41 PM   #8 (permalink)
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I have a Bridgeport Interact rated at 9Hp which I run from a 7.5Hp siemens VFD on single phase without any problem.

I fitted a current meter to the VFD and the only time it gets anywhere near 7.5Hp is if you push the emergency stop button - where I think it puts everything it's got into stopping the spindle!

A 1" deep cut with a 1" cutter in mild steel at about 200mm/min gets up to about 7Hp - but I rarely abuse it like that!

Originally, it would trip the over-current cutout on the VFD when it switched on the spindle. By adjusting the acceleration ramp on the spindle controller - it's fine now but will still reach 4000 rpm in a couple of seconds.

I would just buy the biggest VFD you can afford - but don't worry if it's not quite as high as the motor rating - I doubt you will notice!

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Old 03-05-2013, 08:15 PM   #9 (permalink)
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I put together a 5 HP Rotary, and am on the look out for a 15 HP motor, but that still leaves me with a VFD Issue.

Who ever had this lathe, ripped out all the controls and went with the VFD, SO ....


with a rotary converter and a transformer, I could use the VFD that is on it, I guess.

It originally had a super sweet vacuum tube control scheme, but that is LONG gone.
Ah. So is it still running a gear box for reduction or is it straight drive from that big 10hp motor? 10hp leads me to believe it's straight through but that belt drive leads me the other way.
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Old 03-05-2013, 10:23 PM   #10 (permalink)
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We've got a 20hp pump running on single phase with a VFD, so I know it exists... I also know we paid like five grand for the thing..

On the other hand, in my shop at the house I built a rotary VFD for about thirty bucks with a few freebie contactors and an old motor..


On another note, a VFD really wants to just be running a single motor: you tune it to that particular motor. I just plug whatever I want into the rotary.

VFD's are certainly the class of the league, but they're not the best fit for every shop..

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Old 03-06-2013, 11:43 AM   #11 (permalink)
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I Asked about a Rotary Phase converter here Phase converter - Pirate4x4.Com : 4x4 and Off-Road Forum
And some of yall said go with a VFD.

SO, lets talk VFDs.

I have a lathe with a 10HP / 3phase /208-230-460V Motor (World Motors model # T779A ID# T779-B06-6437-M)

The current setup is wired to 3 phase/ 460 power using a Sumitomo AF-500 inverter.

It has become necessary to change the voltage to 208/230 1 Phase.
Would it be too difficult to swap to a 220 Single Phase motor? (looks like its accessible; and belt driven)
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Old 03-06-2013, 12:19 PM   #12 (permalink)
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Re: VFD as phase converter

All that derate stuff is just a current restriction.

As long as their using diodes on the front end, the single phase will not effect them. After the diodes its just a DC conversion and then the vfd pumps a pulse width modulated DC wave out to your motor.

Just make sure you are powering the control power leads, most of the VFDs build control power from only 2 leads.

We normally use a derate the amperage by half. Toshiba's s11 and s15 VFDs are cheap and will take care of this. The are available up to 20hp.
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Old 03-07-2013, 04:19 PM   #13 (permalink)
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I got my VFD from this place. These are 230 single phase in 230 three phase out: Teco Westinghouse Phase Converter, AC Adjustable Speed Drive Systems, Distributor
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Old 03-07-2013, 09:09 PM   #14 (permalink)
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While 10HP is about the top end of the common range for single phase anything, it is still in the common range. Your VFD is easily possible but you would be looking at a no-name chinese VFD to stay affordable.

For that unit, looking at the pics, you are going to be way ahead in the end by swapping motors. 10HP single phase motors are available. There is some (small amount) of resale value in your current motor. That is your best bet IMO.
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Old 03-08-2013, 03:33 PM   #15 (permalink)
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While 10HP is about the top end of the common range for single phase anything, it is still in the common range. Your VFD is easily possible but you would be looking at a no-name chinese VFD to stay affordable.

For that unit, looking at the pics, you are going to be way ahead in the end by swapping motors. 10HP single phase motors are available. There is some (small amount) of resale value in your current motor. That is your best bet IMO.
I just got a Telemecanique VFD, and i hope I am good to go.
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Old 03-09-2013, 12:07 AM   #16 (permalink)
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I've tricked a few VFD's (allen-bradley 1336 plus) for single to 3 phase by disabling the "incoming line loss" alarm. those drives are getting pretty old now and can be picked up for relatively cheep.
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Old 03-27-2013, 08:41 PM   #17 (permalink)
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Wire sizing.

OK, how do I size the wire.

The motor shows it pulls about 24.6 amps at 230/ 3 phase.

SO, I assume I pull #10 between the VFD and the motor. Sizing the wire for the 3 phase output. OR do I have to size the wire for single phase load?

But what do I pull between the BREAKER and the VFD? I assume 24.6 amps without the power factor.

My algebra is rusty (who are we kidding, it was never good to begin with) what is the formula to back out the power factor?

Thanks.
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Old 03-28-2013, 01:15 PM   #18 (permalink)
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Wire sizing. OK, how do I size the wire.
NEC Article 310.16. There are derating issues that you're probably not familiar with, same with the different wire types. Romex is typically NM, and THHN and THWN are some of the most common types of wire used. You'll notice the chart says #12 THHN copper is good for 25 amps - this is before deration is accounted for. For your uses, figure #12 is good for 20 amps max, #10 is good for 30 amps, etc.

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SO, I assume I pull #10 between the VFD and the motor. Sizing the wire for the 3 phase output. OR do I have to size the wire for single phase load?
Size the wire for the single phase load. You can always increase the wire size, you can rarely decrease. If you're unsure, move to the next size larger in wire. Once you've got it hooked up and running, put an amp meter on it and check each phase to see how much you're actually pulling.

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But what do I pull between the BREAKER and the VFD? I assume 24.6 amps without the power factor.
The VFD should have a nameplate (and if it's new enough, it's own disconnecting means) - check it for the max voltage/amperage the unit will handle. Then remember you're using the equipment for something other than it was originally designed for and increasing wire size won't hurt.
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