Phase convertor

[Hpps]

I'm moving out of my 3ph workshop into the barn at home which is only single phase. I only have a table saw and old Myfold ML8 lathe that are 3ph, so looking to get a phase convertor to power them until I replace the motors with suitable single phase units.

What are peoples recomendations on these convertors? I see Amazon/Ebay units for under £100 and others advertised on Google for £500. Whats the difference and do I need anything specific?

If it's going to cost £500 then I might as well just change the motors, but for now I'd like to go with the cheapest route for reasons.

Thanks

 

[ChaiLatte]

...looking to get a phase convertor to power them...

...I see Amazon/Ebay units for under £100

Research the correct terminology so you know what you are purchasing. A phase convertor is a very different device to a variable frequency drive.

Take a photo of the data plate of both motors as that will have an influence on what is best for your needs.

Three phase comes in two main flavours, semi-skimmed 230v three phase and full fat 415v three phase. Your present setup is a full fat diet. If the motors cannot stomach semi-skimmed, your purchase will have to account for that.

 

[Hpps]

Research the correct terminology so you know what you are purchasing. A phase convertor is a very different device to a variable frequency drive.

Take a photo of the data plate of both motors as that will have an influence on what is best for your needs.

Three phase comes in two main flavours, semi-skimmed 230v three phase and full fat 415v three phase. Your present setup is a full fat diet. If the motors cannot stomach semi-skimmed, your purchase will have to account for that.

I knew it wouldn't be a simple task

 

[clogs]

really depends on what ur future will be.......
are u going to buy more 3 phase machines........and what their HP will be.....?

I have around 10 x 3phase machine...one is a brill 5HP Atlas Copco compessor that'll have to go.....
no chance of proper 3 phase from the mains....
and def to expensive to swop out motors or buy individual units........
I'll be going the digital phase converter route.........
BUT in my situation, only one machine at a time can be used
plus
it's very important to know what ur 240v mains is capable of supplying....
good luck....

 

[ChaiLatte]

I knew it wouldn't be a simple task

It is and can be a simple task. But in order for it to be so, you need to have some familiarity with the language in which the task is discussed and concepts surrounding the issue.

You have a choice: no study time and high expense against two or three hours study and reasonable expense.

 

[Hpps]

It is and can be a simple task. But in order for it to be so, you need to have some familiarity with the language in which the task is discussed and concepts surrounding the issue.

You have a choice: no study time and high expense against two or three hours study and reasonable expense.

I'll take a photo of the tag on the motors and post them up, hopefully that'll get me some info to point me in the right direction.

Without going into too much detail, I'd like to be told I need to get this, this and this, so I can just get it done.

Time is money, and I have neither.

 

[niall Y]

I was in a similar situation to the OP, with three machines working on three phase. For my present workshop I purchased a Transwave converter, which in @ChaiLatte 's analogy would be 'semi-skimmed'. which, if I understand correctly, uses basic technology with feedback from the motor to produce the third phase.
With prices ranging between £700+ to £500+ it is not a cheap option, but I have found it robust and reliable ( 14 years and counting ). The only downside is that you have to trim the controls to adjust after starting.

 

[Spectric]

Look ahead, if you have three phase machines then a digital phase convertor will provide a three phase circuit in which you can connect your machines and without having to modify them in any way. If you buy more machines then they to can be connected and all you need to be aware of is the total load. If going the invertor route you need one per machine, the motor has to be configurable for Delta operation and the machine might need modifying but you get variable speed which may or may not be needed. Fitting single phase motors might reduce the power depending on the machine, there is a limit with VFD's due to regs and again the machine might need modifying. Also for the FLA of a motor a VFD needs to be capable of supplying double this current.

In simple terms ten machines = ten VFD's or one digital convertor again limited by the power available.

I would also only use quality branded invertors and avoid the cheap asian imports because there is a reason for the price difference, having seen VFD meltdowns due to inadequate protection. I would look at ABB or one of the Japanese suppliers like Mitsubishi.

 

[OldWood]

I'm not in the same postion as HPPS, in that I take it he is working professionally, plus I have the advantage of being an electronics engineer so the terminology is in my zone.

The difficulty with single to 3 phase conversion is doing it at a reasonable cost, which includes the headache that the lower cost boxes - Variable Frequency Drive - at ~£100 but will only do one machine, so HPPS would require two of these. There is the option of a Phase Convertor to do several motors, but I have no experience in those.

The next headache is that 3 phase motors are wired in a manner that copes with the 415vac (Full Fat!) - this can be overcome if the motor is reasonably modern (I have a planer from the 1970's that I am restoring and its main drive motor is modern 'enough') by changing over links in the terminal box such that the motor runs in 'Delta' configuration instead of 'Star' such that the motor will take more current but will run on 240vac from a VFD ('semi-skimmed!'). It is possible to so convert an older motor, but it means opening up the motor and locating internal connections to change - I have done that but you need to know a little about what you are doing tha tackle that.

Without knowing the approximate ages of the table saw and Myford lathe I don't think any of us can advise as yet. The Myford, which I am guessing is a nominal 1 HP motor (mine is too tight against the wall to read the single phase motor plate), you might be able to pick up a second hand single phase motor, but the table saw might be more difficult.

So motor plate photos please - and if you can get the covers off the terminal boxes (with the power off!) a photo in them would help too as then we could see if there are just links to change over.

 

[ChaiLatte]

...you might be able to pick up a second hand single phase motor...

There is a mechanical challenge associated with a swap to single phase. Older motors will likely be imperial specification, particularly with an imperial diameter shaft and imperial bore drive pulley to suit that shaft.

A modern single phase metric specification motor is not expensive, but making the pulley fit the motor shaft is where the difficulty appears.

 

[Sideways]

But a single Dunlop pulley and taper lock hub to fit your new metric motor is not expensive from the usual sellers.
Provided the old imperial V belt profile has a close enough metric equivalent so that you can change the motor pulley only when you do the motor....
This is a viable option for saws and planers. Not for stepped pulleys on pillar drills.


Frankly : just buy the digital phase converter and be done with it. Save your time and risk of errors. Leave your machines alone.
You would get away with a smaller size running just a saw or lathe but i'd spend £700 to get the 5kW model and be confident I'd have enough capacity for a two motor P/T and a dust extractor. That's pretty future proof for a 1 man shop.

 

[ChaiLatte]

...just buy the digital phase converter... ...spend £700 to get the 5kW model

Could you point to a source for this item at that price please.

 

[Spectric]

People do tend to simplify motor control when it comes to using electronics and the days of basic star delta starters has long passed since the arrival of the digital signal processor. We have so many options available and it has become a complex subject that is difficult to keep up with, one minute we had AC motors with FOC and feedback sensors and now we have sensorless systems and constant change so looking at a VFD you need to see what motor control algorithms it can provide to suit your application and again the cost is reflected in what it can deliver.

 

[Spectric]

Could you point to a source for this item at that price please.

https://www.jfkelectricalni.com/product/digital-phase-converter-5-5kw-7-5hp-240v-in-400v-out/
I looked at this company a while back but never purchased.

The probem with this sector is that three phase is industrial and domestic is 230 and there is some really grey areas when you look at getting industrial quality equipment to convert single to three phase because industry has no requirement and a lot has been left to John Wayne to deliver.

 

[Hpps]

All of the above makes no sense to the none electrical minded like myself. I could just buy a new sinle ph motor and pulley, there are ways and means of making an old imperial pulley fit a metric shaft, which with my engineering background sounds a much simpler task.

And as for power demand of various machines, I only have the table saw and lathe that are 3ph, and I can only use one of those at a time.

But after a quick google RS came up with these, at various prices, would these be the sort of thing to look at?

https://uk.rs-online.com/web/c/automation-control-gear/electric-motors/inverter-drives/

 

[Spectric]

Those ones you mention from RS are invertors and therefore you will need one for each machine, with just two machines it could be the way forward but not if you start buying more three phase machines which do tend to be heavier industrial machines than a lot on offer today.

If you change the motors you will also need to change the DOL starters and if they have brakes they will not function on 230 volts.

 

[Housey210]

Same situation for me years ago. I bought a static transwave phase converter, 15hp, run a radial circuit from that around unit to isolators and three phase quick release outlets to each machine. In the twenty plus years of using failed once and the company just sent me a new plug and go control unit free of charge, wanting the broken piece back. Attention needed on artificial phase and dol wiring though. If choosing now i would go for the rotary version, which would eliminate triming back controller..

 

[Sideways]

https://www.jfkelectricalni.com/product/digital-phase-converter-5-5kw-7-5hp-240v-in-400v-out/
I looked at this company a while back but never purchased.

The probem with this sector is that three phase is industrial and domestic is 230 and there is some really grey areas when you look at getting industrial quality equipment to convert single to three phase because industry has no requirement and a lot has been left to John Wayne to deliver.

Those are the ones. I've only installed one of it's smaller brothers but the quality seemed better than the typical budget chinese inverter and the manual was half decent.
If I hadn't already spent more than this putting vfd's on my individual machines, I would go this route myself.

But for someone not knowledgable about electrics, the installation should be left to a qualified electrician (and domestic part P installers won't have been taught and may never have seen anything like these). Same goes for your single phase motor swap out : you will need to rewire , maybe replace, the DOL starter and alter the thermal cutout. You've lowered the voltage and put all the power through just one phase instead of 3. The current in that single phase will be much higher. Lots of people get this wrong. There is no solution that is easy AND cheap ....

 

[Spectric]

Don't mention domestic installers, we call them failed electricians that are clueless slaves of the domestic world and new builds.

 

[Hpps]

If I swapped the motor for a single phase motor, surely it would just require a new on/off switch an do away with all the old 3ph electrics altogether?

I won't be buying any more 3ph tools as my barn doesn't have 3ph and I don't plan on having it put in. So whatever route I take will purely be for my 2 existing machines only.