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Pete.
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You wire the inverter directly to the motor for most VFD's. Some can act as a 3 phase converter though.
There's a heck of a nice toolroom lathe going for sale in Bristol for £600. Might be a bit of a brute for what you want though and quite a trek down the M5, but you'll not see another one like it, and you could probably sell the taper attachment on US eBay for the same money.
http://www.homeworkshop.org.uk/index.php?option=com_adsmanager&view=show_ad&adid=15124&catid=2
There's a heck of a nice toolroom lathe going for sale in Bristol for £600. Might be a bit of a brute for what you want though and quite a trek down the M5, but you'll not see another one like it, and you could probably sell the taper attachment on US eBay for the same money.
http://www.homeworkshop.org.uk/index.php?option=com_adsmanager&view=show_ad&adid=15124&catid=2
SBK
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yes mate .
Hopefuldave
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Only just seen this thread, been a bit busy trying to find a.new home for.my workshoppery, which includes a 3-phase lathe....
There *are* a few ways to get a 415v machine running from a.domestic supply, star to delta and a 240v invertor is probably easiest (although the.new control wiring needs thought). My lathe is 415v only so I hacked an old 415v in ABB invertor to run from 240, it is specced for 5hp on 415, copes well with a 3hp motor on 240 (that it thinks is 415...). Another way is to use an old 415/240v welder transformer to step up the input voltage, same derating by 30-50% for single-phase input.
Another way is a 240v inverter feeding a 3-phase 240-415 transformer, kind to the motor, too, as the transformer takes the edge off the inverter output.
More or less all VFD inverters have a soft-start programmable, which is kind to the machine motor and gearing AND the mains supply - apply the derating for single-phase input and compare the revised rating to the lathe's motor, away you go! Only warning I'd give is beware of multi-speed motors, they need some finesse to get working properly without risking VFD damage - it can be done, though, I managed it!
If you may add other 3-phase machines it could be cheaper (but noisier) to use a rotary convertor (a 3-phase motor running as a rotary transformer) - and make 415 with a step-up transformer - but VFDs are getting cheaper, especially used, and motor prices are rising with copper prices hikes.
Dave H. (the other one)
There *are* a few ways to get a 415v machine running from a.domestic supply, star to delta and a 240v invertor is probably easiest (although the.new control wiring needs thought). My lathe is 415v only so I hacked an old 415v in ABB invertor to run from 240, it is specced for 5hp on 415, copes well with a 3hp motor on 240 (that it thinks is 415...). Another way is to use an old 415/240v welder transformer to step up the input voltage, same derating by 30-50% for single-phase input.
Another way is a 240v inverter feeding a 3-phase 240-415 transformer, kind to the motor, too, as the transformer takes the edge off the inverter output.
More or less all VFD inverters have a soft-start programmable, which is kind to the machine motor and gearing AND the mains supply - apply the derating for single-phase input and compare the revised rating to the lathe's motor, away you go! Only warning I'd give is beware of multi-speed motors, they need some finesse to get working properly without risking VFD damage - it can be done, though, I managed it!
If you may add other 3-phase machines it could be cheaper (but noisier) to use a rotary convertor (a 3-phase motor running as a rotary transformer) - and make 415 with a step-up transformer - but VFDs are getting cheaper, especially used, and motor prices are rising with copper prices hikes.
Dave H. (the other one)
brightspark
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the reason second hand 3 phase motors are rising with price is because of the converters 
u couldnt give them away before they were available
u couldnt give them away before they were available
Wedg1e
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My Boxford VSL came from a school in Retford, I bought it from the guy who took all their lathes, he had a garage full of them!
The gearbox selectors were stuck fast, having apparently not moved in years. There is some wear on the bed and leadscrews etc. but tolerable for my purposes... it suffers from the usual Boxford affliction of chipped paint.
My Bridgeport 1ES mill was from a college in Bradford or Barnsley, I forget which: it was one of the first things I ever bought via Ebay, when you could still get bargains. Although it was missing two covers from the base (and, frustratingly, had no vertical head with it) it was (still is) in pretty good condition for what is now a 33-year-old machine. It only came with one cutter, a vice and the over-enthusiastic college safety guard. There is sod-all play in the leadscrews, a couple of the feed handles got broken by the carriers but apart from that it was £265 well-spent
Wedg1e
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the reason second hand 3 phase motors are rising with price is because of the converters
Too right: I sold the 3-phase motors from my dust extractor and bandsaw for a pound each
as that's all anyone bid for them.Hopefuldave
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Hi Mark,
Shouldnt be too much trouble unless you want to switch motor speed on the fly, if so you need a VFD with 'gate block' to drop the VFD output while you change - on mine there's a microswitch on the 3-speed switch lever to do this. The other issue is that the motor current may be very different for the two speeds - a lot of VFDs can be set up with two or more sets of motor parameters under control of one of the digital inputs so they cope with this.
You could, of course, leave it in the high speed and use the VFD to vary speed - most do it that way, but I wanted to retain the look and feel of my 3-speed motor x 2 x 2 (so 12 speeds) lathe and maintain torque/power at reduced speeds by using the motor as it was designed...
If the Warco motor definitely is 220/415, that's handy as you'll find a 240-in, 240-out VFD a lot less spendy than a 240 to 415!
Be aware, though, parts for older far-eastern imports can be hard to find, the 1440 will be some years old and the importers may no longer deal with the factory, they all chop and change sources... A thorough inspection should be part of the buying process! It's worth enquiring about parts availability, too, maybe you can get a spares price list? Ask about things like feedshaft worms and gears etc, the bits that aren't simple to make your own.
Dave H. (the other one)
Shouldnt be too much trouble unless you want to switch motor speed on the fly, if so you need a VFD with 'gate block' to drop the VFD output while you change - on mine there's a microswitch on the 3-speed switch lever to do this. The other issue is that the motor current may be very different for the two speeds - a lot of VFDs can be set up with two or more sets of motor parameters under control of one of the digital inputs so they cope with this.
You could, of course, leave it in the high speed and use the VFD to vary speed - most do it that way, but I wanted to retain the look and feel of my 3-speed motor x 2 x 2 (so 12 speeds) lathe and maintain torque/power at reduced speeds by using the motor as it was designed...
If the Warco motor definitely is 220/415, that's handy as you'll find a 240-in, 240-out VFD a lot less spendy than a 240 to 415!
Be aware, though, parts for older far-eastern imports can be hard to find, the 1440 will be some years old and the importers may no longer deal with the factory, they all chop and change sources... A thorough inspection should be part of the buying process! It's worth enquiring about parts availability, too, maybe you can get a spares price list? Ask about things like feedshaft worms and gears etc, the bits that aren't simple to make your own.
Dave H. (the other one)
Thanks Dave,
I've had a closer look at this lathes motor and it is plated 415v so it looks like I will need a 240v to 415v inverter, although it states on the motor plate star delta and gives wiring details inside the cover. I have attached a couple of photos in the hope someone can make some sense of them. I am afraid this is starting to go over my head. I had a look at the price for 240 - 415 inverters - seems to me that replacing the motor with a 220v 3 phase and a 240 -220v inverter is the much cheaper option, or am I missing something?
I've had a closer look at this lathes motor and it is plated 415v so it looks like I will need a 240v to 415v inverter, although it states on the motor plate star delta and gives wiring details inside the cover. I have attached a couple of photos in the hope someone can make some sense of them. I am afraid this is starting to go over my head. I had a look at the price for 240 - 415 inverters - seems to me that replacing the motor with a 220v 3 phase and a 240 -220v inverter is the much cheaper option, or am I missing something?
Why would you go this way and have to buy a 240 volt 3 phase motor and inverter why not just buy a 240 volt motor?? I think I know the answer but I will await replies with interest
Hopefuldave
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Mark, I can see where the confusion comes in...
As I.suspected, it has a pole-switching motor to get the two speeds - makes it trickier to run from 240, but not impossible.... As for why, stepless speed control, dynamic braking to name just two
That motor, like the dustbin-sized BTH I have, is 415 only, so you'll need to feed it 415 to get a worthwhile amount of torque/power.
Method I use is to hack an older 415 3-phase input VFD - older is.better in a couple of ways, most importantly they used.two banks of reservoir capacitors, so it's relatively easy to modify 'em by moving the 240 neutral to between the banks. This is known as a voltage doubler, and fools the VFD into seeing 480 coming in so it'll deliver enough out to drive the motor to full current - Sounds easy, and it is *if you know what you're doing*
Downside is that it increases the ripple current in the capacitors, shortening their lives, and you have to derate the VFD some - I'm using a 5hp (3.8kw) VFD on a 3hp (2.2kw) motor, works pretty well - plus it cancels all the approvals (CE, UL etc.) - if you consider doing it this way, find a friendly radio ham or such to help if you're unsure what to put where! This is, incidentally, how a lot of the 240 to 415 VFDs are modded from straight 415 by certain vendors...
My used 415v VFD cost me all of £25 from ebay, the 415 input ones aren't as desirable...
Another way, use a 415 VFD, but feed it 415 single phase, using a redundant dual-voltage welding transformer to step up the voltage - again you need to derate the VFD as you're only using part of the 3-phase rectifier. Yet another, a 240 VFD with a 3-phase transformer on the output, a 3kva isolating transformer will do it, e.g. Delta in, star out.
Hope that makes sense!
Dave H. (the other one)
As I.suspected, it has a pole-switching motor to get the two speeds - makes it trickier to run from 240, but not impossible.... As for why, stepless speed control, dynamic braking to name just two
That motor, like the dustbin-sized BTH I have, is 415 only, so you'll need to feed it 415 to get a worthwhile amount of torque/power.
Method I use is to hack an older 415 3-phase input VFD - older is.better in a couple of ways, most importantly they used.two banks of reservoir capacitors, so it's relatively easy to modify 'em by moving the 240 neutral to between the banks. This is known as a voltage doubler, and fools the VFD into seeing 480 coming in so it'll deliver enough out to drive the motor to full current - Sounds easy, and it is *if you know what you're doing*
Downside is that it increases the ripple current in the capacitors, shortening their lives, and you have to derate the VFD some - I'm using a 5hp (3.8kw) VFD on a 3hp (2.2kw) motor, works pretty well - plus it cancels all the approvals (CE, UL etc.) - if you consider doing it this way, find a friendly radio ham or such to help if you're unsure what to put where! This is, incidentally, how a lot of the 240 to 415 VFDs are modded from straight 415 by certain vendors...
My used 415v VFD cost me all of £25 from ebay, the 415 input ones aren't as desirable...
Another way, use a 415 VFD, but feed it 415 single phase, using a redundant dual-voltage welding transformer to step up the voltage - again you need to derate the VFD as you're only using part of the 3-phase rectifier. Yet another, a 240 VFD with a 3-phase transformer on the output, a 3kva isolating transformer will do it, e.g. Delta in, star out.
Hope that makes sense!
Dave H. (the other one)
Pete.
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Why would you go this way and have to buy a 240 volt 3 phase motor and inverter why not just buy a 240 volt motor?? I think I know the answer but I will await replies with interest
Because a single-phase motor is the Briggs & Stratton of the electric motor world. It's the simplest way but no the best.
Hopefuldave
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Briggs & Stratton? That good? I take it you're thinking of Western World production..
Realistically, a 3-phase motor with or without a VFD will be quieter, smoother and will give a better finish to the work - a good (non-Chinese!) DC motor can be better, but costs come out a touch higher once you factor in a decent DC controller. Single-phase motors are ok, I guess, for less critical uses, but no speed control, dynamic braking (a real bonus) etc.
One of the best mods for a decent sized 'import' machine tool (if you can find one that's decent quality or treat it as a 'kit' and start with a rebuild), and one of the most common after quick-change tooling, is fitting a 3-phase motor / VFD, it really makes a lot of difference to usability and results... After that it's fitting a decent DRO, I'd say.
Just my ha'pennorth,
Dave H. (the other one)
Realistically, a 3-phase motor with or without a VFD will be quieter, smoother and will give a better finish to the work - a good (non-Chinese!) DC motor can be better, but costs come out a touch higher once you factor in a decent DC controller. Single-phase motors are ok, I guess, for less critical uses, but no speed control, dynamic braking (a real bonus) etc.
One of the best mods for a decent sized 'import' machine tool (if you can find one that's decent quality or treat it as a 'kit' and start with a rebuild), and one of the most common after quick-change tooling, is fitting a 3-phase motor / VFD, it really makes a lot of difference to usability and results... After that it's fitting a decent DRO, I'd say.
Just my ha'pennorth,
Dave H. (the other one)
scottmk1
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Hi, ive just got a Boxford with a 3 phase dual voltage motor, rated at 1.5hp/1.1kw. I'm thinking of buying this inverter with remote controller - http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=181129150673&ssPageName=ADME:X:RTQ:GB:1123
Is this a good deal? Also, if the inverter is to be connected to the motor only, how can I go about powering the coolant pump and work light?
Is this a good deal? Also, if the inverter is to be connected to the motor only, how can I go about powering the coolant pump and work light?
Thanks for all your input, it is soooooo much clearer now
I thought I'd share this with you as it came through the door this morning.
After reading this I don't feel quite so sad about spending £1000 ish on a converter/inverter.
The way I see it is if I get this lathe I either need a:
Static Converter £462(Transwave)
Rotary Converter £792 (Transwave)
or a 240 - 415 inverter £1250 (Drives direct)
or replace the motor and use a 220v inverter £450 - £600 ish
At the moment I am leaning towards the rotary or the Drives direct inverter as I know I will want a mill as soon as I get a lathe up and running.
I thought I'd share this with you as it came through the door this morning.
After reading this I don't feel quite so sad about spending £1000 ish on a converter/inverter.
The way I see it is if I get this lathe I either need a:
Static Converter £462(Transwave)
Rotary Converter £792 (Transwave)
or a 240 - 415 inverter £1250 (Drives direct)
or replace the motor and use a 220v inverter £450 - £600 ish
At the moment I am leaning towards the rotary or the Drives direct inverter as I know I will want a mill as soon as I get a lathe up and running.
OK I am not too sure how much the single phase would loose quality. I had a Raglan 5 inch with a 240 single phase motor. This cut well and finish was great but it was obviously limited in size and this colchester has DRO and is way way bigger. Now I need to move out of my unit and go back to the garage.
I checked out the motor and its a GEC . seems to be 240/415 so I am hoping I can go the cheaper route. Its a 3.7KW . The lathe has a clutch on it and many many speeds via a gear box so I am hoping start up power does not have to be massively over rated.
Whats the cheapest/safest route I should take??
Hopefuldave
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That looks an easy motor to use... As long as you can find a 240 single-phase input VFD rated for the power requirement, a lot of single-phase stop at 3hp/2.2kw...
If you're not planning on using the full 5hp, you could probably just about get away with a 3hp VFD, and use the clutch, although you may have problems at the highest speeds - a 3hp VFD may not deliver enough current and motor torque if the headstock's a bit tight. A possible way around this, I've heard, is a smaller motor pulley and increasing the rpm with the VFD... Not tried it myself, haven't needed to!
A good addition would be an external braking resistor, so when you pick your VFD see whether it will take a simple resistor or needs a "brake unit" - they'd be a lot more expensive as they're VFD-specific (so manufacturer's prices, not generic Chinese £30 from eBay) and have a "brake chopper" built into the unit, not the VFD.
The motor voltage change is almost obvious - take off the links along one side of the terminal block, to be sure all's standard check for continuity from one terminal to its 'pair', shouldn't be any, then strap the pairs together, you have 240v delta!
Dave H. (the other one)
If you're not planning on using the full 5hp, you could probably just about get away with a 3hp VFD, and use the clutch, although you may have problems at the highest speeds - a 3hp VFD may not deliver enough current and motor torque if the headstock's a bit tight. A possible way around this, I've heard, is a smaller motor pulley and increasing the rpm with the VFD... Not tried it myself, haven't needed to!
A good addition would be an external braking resistor, so when you pick your VFD see whether it will take a simple resistor or needs a "brake unit" - they'd be a lot more expensive as they're VFD-specific (so manufacturer's prices, not generic Chinese £30 from eBay) and have a "brake chopper" built into the unit, not the VFD.
The motor voltage change is almost obvious - take off the links along one side of the terminal block, to be sure all's standard check for continuity from one terminal to its 'pair', shouldn't be any, then strap the pairs together, you have 240v delta!
Dave H. (the other one)
Ok what does this one seem like?? http://www.ebay.co.uk/itm/VARIABLE-FREQUENCY-DRIVE-INVERTER-VFD-NEW-5HP-4KW-c8-/260708447137?pt=UK_BOI_Industrial_Automation_Control_ET&hash=item3cb36f33a1
Its almost disposable price....which makes me think its not going to be up to the job.
. BUT I also know of suppliers who up the price so you think its better quality.. ;(And then there is this one. http://www.ebay.co.uk/itm/UPDATED-7-5KW-220V-10HP-34A-VFD-VARIABLE-FREQUENCY-DRIVE-INVERTER-CE-/251033322334?pt=UK_BOI_Industrial_Automation_Control_ET&hash=item3a72c0835e
Hopefuldave
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Ok, Chinese so they *could* be of indifferent quality, but either should do the job. If you can, get 'em to email you the installation guide before you buy, the quality of info makes a big difference at setup time!
Both use a braking resistor rather than a chopper, check out what resistance and power rating they need - generally the lower the resistance the higher the power and the more braking you can configure - proper *emergency* stops need a high peak power rating, repeated fast "routine" stops need a high average power... As an example, on the ABB VFD I use, a 100 Ohm 1kw resistor does a fine job, for instance a nearish instant stop (a few turns of a hefty all-steel 10" 4-jaw at 200 - 300 rpm, handy when fwd-rev cutting metric threads on an imperial lathe, seemingly instant with collets and a small workpiece -YMMV), repeatedly. The resistor was under £30 including shipping from China... The VFD cost less than that, but was a bit of a lucky break!
Dave H. (the other one)
Both use a braking resistor rather than a chopper, check out what resistance and power rating they need - generally the lower the resistance the higher the power and the more braking you can configure - proper *emergency* stops need a high peak power rating, repeated fast "routine" stops need a high average power... As an example, on the ABB VFD I use, a 100 Ohm 1kw resistor does a fine job, for instance a nearish instant stop (a few turns of a hefty all-steel 10" 4-jaw at 200 - 300 rpm, handy when fwd-rev cutting metric threads on an imperial lathe, seemingly instant with collets and a small workpiece -YMMV), repeatedly. The resistor was under £30 including shipping from China... The VFD cost less than that, but was a bit of a lucky break!
Dave H. (the other one)
