How much of a problem is 3-phase?

[skotl]

So I've spotted a handful of items for sale on here and in other places, but they're 3-phase.
My tendency is to go "Uugh! I'm not a factory - steer clear!"

Is that unreasonable? Am I cutting myself off from some bargains?

What is involved in getting three-phase from single-phase? What needs to be bought, and how much is it likely to cost?

My garage is fed with a 63A supply, currently broken out to a 5A light, 20A socket ring and a 32A socket for the welder. Can I feed a 3-phase converter thingy from one of these?

Cheers
Scott

 

[piman]

Hello Scott,

a lot depends on the size of the equipment you are interested in. Small machine tools can be easily powered by a solid state converter for not too much cash as long as it has a dual voltage motor. Larger size equals higher cost.

Alec

 

[Rig Pig]

I don't think motors are a problem, you can get true 415v inverters that are simply plug and play. I doubt that they will run a welder or plasma cutter.

 

[Maker]

I doubt that they will run a welder or plasma cutter.

Why not? Like you said, it's true 415v power, surely it would be fine provided you kept it at 50Hz.

 

[steviec_lj]

Watching this with interest, as I've turned down quite a few items simply because they are 3ph.

 

[langy]

I run quite a bit of 3phase stuff and it works so much better than single.
I use a 4hp inverter from Drives direct, had it nearly 10 years now, best £400 I ever spent, they are even cheaper these days

 

[Rig Pig]

Why not? Like you said, it's true 415v power, surely it would be fine provided you kept it at 50Hz.

well, I'm not a spark but big transformer welders are not nice to drive, they have a poor power factor. I suppose if you had a decent quality one speced to the set it may be ok. A mate of mine has a garage with a 3ph ramp that has a whole workshop converter with 'no welders' on the data plate.

 

[skotl]

Thanks guys - it was mainly motor stuff I was considering; a fume extractor initially, and (much further down the road) lathes, milling machines, etc.

 

[AndyStobbs]

Just put single phase motors on and be done with it. A fume extractor motor is smaller than a 3hp compressor motor. My fume extractor is badged 2.2kw on 110v but the actual motor is only 0.75Kw - the rest being used for the electrostatic precipitator.

My lathe had some tiny little 1kw ish single phase motor on it, which I ditched and went for three phase but the point is it wasn't a big motor.

Not sure about the size of my mill motor, but its not on gigantic wiring, and the first thing that happens is a reduction from motor speed to 600rpm before any drive is taken off the shafts.

Three phase motors are smoother, but realistically I'm not turning out aerospace quality components on my half century old equipment.

 

[GrumpyOne]

I know nothing about this kind of stuff but I am intrigued by this thread and the ability to run 3 phase machines off of a domestic supply.
Is a frequency inverter like this one the same thing as we are taking about, would it do the same thing if it's not?

 

[langy]

I know nothing about this kind of stuff but I am intrigued by this thread and the ability to run 3 phase machines off of a domestic supply.
Is a frequency inverter like this one the same thing as we are taking about, would it do the same thing if it's not?

This is the one I have , they seem to have gone up a little http://www.ebay.co.uk/itm/3-HP-DIGI...867?pt=LH_DefaultDomain_3&hash=item5894a47ccb

 

[mr migwire]

I put this in the garage a while back running directly from a spare 25A in the consumer unit, it runs my power hacksaw quite happily and is the same size I had for my lathe, you just have to make sure the item you want to run is dual voltage 3 phase and within the HP rating of whatever invertor you choose.

http://www.ebay.co.uk/itm/281258983718?_trksid=p2060778.m2749.l2649&ssPageName=STRK:MEBIDX:IT

 

[GrumpyOne]

The ABB Single phase Inverter Drive seems to be the same thing, or at least do the same job, but my knowledge is very limited about these things, in fact I don't have any knowledge about them , what I do have is someone that works for ABB and should be able to get me a hefty discount, which is why I am keen for ABB stuff.

 

[brewdexta]

I had a 2HP Mitsubishi 240 1PH to 240 3PH inverter that went with the lathe I sold to maker and I have a similar Allen and Bradley inverter for a Tom Senior M1 mill

good points

• variable speed control and nice things like jog and reverse and soft start - worked a dream on the Chipmaster
  
• Can be used for braking with ballast resistors
  
• Relatively cheap and allow you to use 3PH gear that is generally better and cheaper than 1PH
• New 3PH motors are relatively cheap and no messing with strt/run capacitors

bad points

• You need a dual voltage 3PH motor i.e. it need to be configured to Delta. Older motors tend to be star only (or dive into the windings and find the star point and break it out )
  
• Older motors converted to delta i.e. 1950s/60s motors don't seem to have much grunt in my experience - may be just bad luck on my part
• At lower speeds you do lose power, better to use a back gear on your machine and keep the motor rpm up a bit
  
• You generally need one per machine if your doing stuff like variable speed etc. as you need control wiring and the VFD setting may be individual to that machine, not impossible to share but a bit of a pain

The reason I'm moving to 10HP 240 1PH to 415 3PH inverter are

• I needed variable speed on the chipmaster as I had ripped out the variator that provided speed control and replaced it with a new motor - no longer needed
  
• My new lathe and my mills have built in speed controls so I can move to a whole workshop system where the VFD settings are static
• The new VFD has a soft start input feature to lessen any dimming of lights in the house when big monster motors start up
• I don't have to change any motor settings, plug and play for new and old motors (assuming they came from a 415v world)
• It will drive the main motor and the suds pump on the lathe simultaneously, just start the big-un first so no changes to lathe wiring
  
• I can wire out to as many circa 3HP machines as I like plus the 7.5HP monster as long as I only use one at a time

bad points

• Needs a 50A breaker and associated beefed up cable, I have some 6mm SWA that needs swapping to 10 possibly 16mm. I could possibly get away with a 32A with the soft start but may as well do it right
• Expensive, but I hope to recoup the cost over a few years by only needing one VFD and saving on the machines I buy

Costs come down considerably with HP and also breker/cabling requirments and if Langy is OK with 4HP then I'm guessing most will be fine with that. I've just acquired a big compressor for nowt, not sure of the HP yet however I think even a 10HP VFD may struggle at start up as there's no clutch to lessen the load. We shall see

Cheers
Andy

 

[Rig Pig]

I have 3 phase in my house, I don't know what it would cost to have installed as it was there when we moved in, I have a feed to my workshop giving me similar power to an industrial unit.

 

[brewdexta]

I have 3 phase in my house, I don't know what it would cost to have installed as it was there when we moved in, I have a feed to my workshop giving me similar power to an industrial unit.

I'm jealous

 

[skotl]

This is the one I have , they seem to have gone up a little http://www.ebay.co.uk/itm/3-HP-DIGI...867?pt=LH_DefaultDomain_3&hash=item5894a47ccb

Wow! £500? That would more than wipe out any potential savings in buying used unloved 3 phase kit.

I put this in the garage a while back running directly from a spare 25A in the consumer unit, it runs my power hacksaw quite happily and is the same size I had for my lathe, you just have to make sure the item you want to run is dual voltage 3 phase and within the HP rating of whatever invertor you choose.

http://www.ebay.co.uk/itm/281258983718?_trksid=p2060778.m2749.l2649&ssPageName=STRK:MEBIDX:IT

Ah - that's more like it!

 

[squazy84]

most of our equipment is 3ph and a lot of it built before 1950, the equipment is usually more robust and the motors last a lot longer in my experience,we have 3 ph from the mains so its was a no brainer, we have a large compressor with a 3ph motor starting under load without any form of service apart from lubrication for the last 20 years,in use 6 days a week,both welders are 3ph and the same goes zero trouble built for industrial use and were not expensive to buy,also 3ph is charged at a lower rate in Ireland so its cheaper.

 

[Wedg1e]

This is the one I have , they seem to have gone up a little http://www.ebay.co.uk/itm/3-HP-DIGI...867?pt=LH_DefaultDomain_3&hash=item5894a47ccb

Same as the one I use to run multiple machines, I paid £250 for mine second-hand from an Ebay seller with good feedback, it's been 100%.

 

[Wendelspanswick]

All this talk of static converters and VFD'S has given me a brainwave, I have a 8hp 415v static converter that runs my universal woodworking machine, if I take the output direct from the transformer in the static and feed it into a suitable VFD it would give me a true balanced 3 phase supply with all the benefits of a VFD.
Looks like a suitable VFD with a 380v input would be around the £250 mark.