Using an inverter 240v single phase/ 440v three phase

[Bob StrawsonParticipant @bobstrawson49673]

Hello, I'm new to this site and wonder if anyone has experience using a phase converter from 240v single phase to 440v three phase on a lathe with a 3HP motor(single speed).

I'm considering buying a Smart and Brown 1024 VSL. The main spindle motor is 3HP plus a small motor for the variable speed drive and the coolant pump, (.25hp?). It also has an "inch" function. Ideally I would to put the three phase output to the terminal in the machines but is this how they work. I won't need any speed variation function.

Looking forward to hearing your experiences,

Bob Strawson

[Bob StrawsonParticipant @bobstrawson49673]

[john fletcher 1Participant @johnfletcher1]

Morning Bob, if you go onto Homeworkshop.org site there has been much discussion about what you are after. Apparently 415 in and out inverters are not so expensive, some have carried out a mod to convert that type to 240 in and 415 out. Its a very interesting site lots of good information, also you can advertise any thing you might have for sale free of charge.John

[David Clark 13Participant @davidclark13]

If you need to run more than one motor you need a particular type of of converter. I can't remember if it is a static or rotary converter but I am sure someone will let you know.

[KWILParticipant @kwil]

David,

You can use an Inverter type with more than one motor if the second motor is relatively small, ie the suds pump. I do.

[Clive FosterParticipant @clivefoster55965]

My Smart & Brown 1024 VSL runs just fine off one of Drives Direct 10 Hp "whole shop" plug and play inverter boxes. These units have a large short term overload capability so you can use them like a proper mains 3 phase supply with the box running at 50 Hz and using the machines own switchgear to control it. Expensive but its the easy way and lets you install other 3 phase machines without worrying. About the only issue is that the maximum start load when used like this is about half the rated power. So mine shouldn't be used to start any motor above 5 HP or thereabouts. If you use an inverter direct wired to the machine motor it should start an unloaded motor up to its rated power but obviously that is when winding up from zero over a few seconds. There are a few inherent issues with the conversion from 240 to 415 output which tends to reduce overload capacity and therefore starting ability but nothing that sensible over-rating won't deal with. Selecting a 3 HP box to run a 3 HP motor may well be OK but sometimes not and home shop guy is rarely in a position to figure out whether the planned application slips into the sometimes not band. Compressors almost certainly will tho'. My Hydrovane is fine.

The Smart & Brown VSL switchgear and contactor arrangement is comprehensive, effective and to industrial standard. It will take a bit of digging and minor jiggery-poking to re-arrange things to run an independent inverter drive direct to the main motor in the standard manner. VSLs come in 3 wire and 4 wire electrics variants. With the 3 wire system the speed change and pump contactors are effectively powered off the motor input lines so should work OK as standard providing you let the main motor come up to speed first. The 4 wire ones connect the contactor coils between a motor feed line and neutral. Which may be problematical with some converted 240 in 415 out inverters as many aren't well behaved at the neutral (star centre) point. A neutral may not actually be provided. Mine has a neutral but the power rating is very low. Far as I can see its fairly straightforward to go from 4 to 3 wire layout. The standard forward / reverse start and stop push buttons have very high quality switches underneath which should do fine to control a directly connected inverter.

If I were going for direct connection I'd put a 5 HP box on. The VSL has no clutch so needs to run-up under load.

If the VSL is in good condition stop considering and go and buy it. Its as good a machine as you can get in that size. As ever some niggles. A spindle clutch would be nice as would a single tooth clutch in the screwcutting train as per Holbrook, Pratt & Whitney and Hardinge. Metric & imperial threading in the box would be good especially as changing over is a faff as standard, but I have a fix for that. Only one drive for both longitudinal and cross power feed so you have to switch over makes one more thing to forget too. Hafta remember to wipe out under the saddle properly after using coolant as it tends to sweep liquid under the saddle leaving marks and eventually corrosion. All pretty minor against the virtues of massive strength, great accuracy and fundamental simplicity. Mine was clearly rode hard and put away wet far too often over the years but performance is still well up to scratch even if the cosmetics are untidy.

Clive.

[Clive FosterParticipant @clivefoster55965]

Ooops, forgot about the inch function. When turned on the hold in contacts on the main motor contactor are taken out of circuit so the motor only runs when the forward (or reverse button) is held down to keep the contactor coil energised. As soon as you release the button the contactor drops out and the motor stops. Works fine with my whole shop plug and play set-up but clearly won't go with the conventional dedicated inverter connected direct to the machine and controlled via its own switches either on the box or via the remote switch input terminals.

No great worries as the inch function is not something you will miss. In several years ownership I've operated it twice on mine. Once to confirm what it actually did as the manual said nowt and once to show off to a shop visitor who asked what it was. If you need to move things round a bit its far easier to pull it out of gear by setting the direct drive / backgear lever to the middle position and turning the chuck by hand.

Clive.

[Bob StrawsonParticipant @bobstrawson49673]

Very many thanks for your prompt and useful replies, especially Clive whose answer is more comprehensive than I could have hoped for.

I have the wiring diagram from Bracehand Ltd and it does seem quite simple to modify it to three wire if it's four at present.

I just got back from seeing machine for the first time and while I couldn't really see much wear on the slides, possibly because of the lube system, it's certainly been carelessly used with dinks and marks, a bad repaint job and limited tooling, too much of some things and quite a few things missing that I'll need to buy but loads of Hardinge 5C collets. I remember that they used to be quite expensive but are now around £5 each.

One thing; the speed varying motor didn't work and I presumed that it was not wired in as they'd just stuck the wires in temporarily to an outlet, now looking at the diagram I see that it's powered from the main motor. I'm going to assume that it's just something simple anyway, I think.

It's rather scruffy and scuffed but should scrub up ok, the seller and I just need to agree the price which is difficult as they seldom come onto the market. The mk1 version seems more common and go around £2,000 to £2,500 but I really like the VSL better. If anyone has an opinion on that I'd appreciate hearing it.

Thanks again,

Bob Strawson

[Clive FosterParticipant @clivefoster55965]

Hi Bob

Glad to be of help. Easy enuf as I'd done the same looking into things when I got mine. The four wire system has 220 V (nominal) contactor coils so probably easiest to run them off an independent supply direct from the mains. But you must have some sort of electrical interlock to ensure that you can't run the speed adjustment motor unless the main motor is running. Its an expanding / contracting pulley (Reeves) drive and the belt won't like it. Or use a capacitive voltage divider to drop the voltage down from 415 and connect across the main motor as per the 3 wire system. Need to find someone up on such things if you do tho'. I've used the idea elsewhere but cookbook fashion only.

Another thing to check is the condition of the coolant reservoir. Prone to rust out with pinholes round the bends. Which grow alarmingly if shown a welder. Did a temporary fix on mine with glass fibre tissue and too much resin. Which, as usual, looks like being permanent. The beast is far too heavy to pull out from the wall unless I have to.

As to prices my metric version cost me £1,100 or thereabouts by the time I'd got it home from the dealer. Plus £300 odd for a taper turning unit and £150 (ish) for the gears to make up a full metric to imperial conversion set. HPC do stock gears in correct DP near enough the right thickness. Had to get collets too so probably have around £2,000 in it not counting the extra toys which logical man doesn't need but I'm the sort of guy who does. Sounds like it was in better nick than the one you are considering. No dings and negligible wear. I'll try and find a picture if you like.

Clive.

Edited By Clive Foster on 21/07/2015 21:30:46

[Bob StrawsonParticipant @bobstrawson49673]

Hi Clive,

I'm sorry to be taking up a lot of your time.

The seller of the machine I'm looking at started at £4995! Came down easily to £3800 but can deliver to me in South Devon. I'm not sure how far he'll go but I would like it. There are 90 odd 5C collets and a set of Multibores too, not that I like those much although they do go up to 1.25" dia. It has no gears except the three on it, 35/120/127 so I will need a few of those. That, with a three and four jaw chucks is it! There's a MK 1 on eBay at £2700, or offers.

Thanks for the info on the speed varying motor, I had a Raglan years ago with the same idea but lever operated and of course the Hardinge is the same but motorised, I've had a few of those, fabulous machine but limited in many ways. And the DAF cars which I seem to remember had problems, you can't put too much power through them, the pressure spring on the idle side winds up and slips.

I'll let you know what happens, I hope I don't do anything silly, again!

Bob

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