Thread: fitting single phase motor to old 3 phase lathe

Many people will have done this.

The alternative is to purchase a single phase to 3Phase converter also called a Variable Frequency drive.
This allows you to change speeds without changing belts plus a whole lot more.
It does rely on you either having a knowledgable and budget cost sparky OR some familiarity with Mains Power.
If you can do it yourself it could cost about the same as for a single phase motor - if not it could cost 2-3 times more than a single phase motor.

I've used Conon motors on some machines and found them to be reliable
see 0 75KW 1HP 1400PM Shaft Size 19mm Electric Motor Single Phase 240V | eBay

if its an ex-school lathe, there is a high likelihood its a woodfast ?

its dead easy to change to single phase, but like BobL mentioned the way to go now is to convert it using the method he describes, variable gives some great advantages. if it does happen to be a woodfast lathe you can give them a call and there is a chance they will have a kit to do the job, costs about 1k but don't quote me on that (might be 1600), that cost might include it being taken in to them and having them do it as well. i remember (not very well as you can tell) because i spoke with them only a couple of months ago about the exact same thing. and they used to advertise kits converting their lathes for while just prior and for a while after they started selling their variable models. but last i spoke with them (not long ago) they can still accommodate you.

cheers
chippy

p.s. i think the cost i am talking included a 3 phase motor. my query involved changing it back to 3 phase so it could have the variable

Different electrical system here but I have looked into it.

As a side note, many equipment manufacturers make their equipment dual phase capable. My Grizzly band saw is wired for three phase but is single phase machine. What happens for single phase is that L1 and L2 are used with L3 ignored in the switch. For single phase, L1, L2 and ground are wired to the power cord. The single phase motor is wired to L1, L2 and ground. For three phase, L1, L2, L3 and ground are wired power cord and motor.

There are a couple of other considerations.
~ If the off / on switch is of the magnetic variety, L1 usually supplies the electrics for the magnetic part of the switch. The magnetic switch prevents the machine from restarting if power was lost. Your three phase electrical system is different than ours and magnetic switches may behave differently than ours.
~ If the lathe has an electronic speed control, ignore everything above because I don't know.

The main issue is to get a single phase motor with the same "frame" designation. It should bolt right in.

OK, sorry to bump this after some time, but I'm looking at going the VFD option. However.....in talking to Conon Motors, he's raised an interesting point, that being if you use a VFD on a 3 phase motor, then that motor's power output is diminished ( due to the lower voltage ), so a 415v 1HP rated 3 phase motor running on a VFD being powered on 240v is probably going to be more like a 0.58HP output.

So I'm looking at buying a new and bigger 3 phase motor ( 3HP which would be equivalent to 1.73HP on the VFD ) and a VFD along with a new pulley to fit the larger motor which in total will come to ~$500. Then i need to get an electrician to hook it all up.

The VFD will then also be the ON/OFF switch - however I'm thinking I'd like some kind of Knee/foot operated switch, especially to turn it off incase of an emergency etc.

I'd then need to build a new stand, engine mount etc and use some maths to figure out the various speeds given new pulley on the motor, and what Hertz on the VFD = what speeds on the lathe!

I figure if I can spend $500 and have a big cast iron lathe with VFD, then that's probably money well spent, as it seems something of similar size, robustness and with VFD tends to have atleast price tag that starts with a '2' and has 3 zeros. Happy to post photos of the beast if anyone is interested.

Any opinions? Just trying to get some feedback before I drop $500 to make sure I'm not making a mistake!


Cheers

Seb

Originally Posted by Sebastiaan76

OK, sorry to bump this after some time, but I'm looking at going the VFD option. However.....in talking to Conon Motors, he's raised an interesting point, that being if you use a VFD on a 3 phase motor, then that motor's power output is diminished ( due to the lower voltage ), so a 415v 1HP rated 3 phase motor running on a VFD being powered on 240v is probably going to be more like a 0.58HP output.

That's not the way it would be done.
What you need is a motor that is able to deliver full power using 240V 3Phase (3P).
As these motors are the standard 3P motors used in 110V SP countries they are relatively common and many 3P motors can run on both 240 and 415V 3P
It turns out that 415V 3P motors that are connected in a so called "star" or "Y" connection mode can often be reconfigured to "∆" connection, and will this deliver full power on 240V 3P.
Sometimes this can be done inside the mains connection box on the motor, while on other motors the reconnection may require internal motor surgery (not recommended for DIY) but can usually be done by a motor rewinder.

The reason for using a bigger motor is more related to running at reduced speeds as the power delivered by a 3P motor using a standard VFD is proportional to frequency.
At 25Hz the speed is reduced by half compared to 50Hz and so is the power. At 12Hz the speed and power will be about 1/4 of the standard 50Hz speed.
I would not recommend going lower that this speed for continuous use as the motor may get too hot.
At higher speeds the motor power stays more or less constant up to about 100Hz (double speed) and after that the power drops off due to frictional effects.
This gives you a thereoatical speed range of 12 to 100 Hz which is a range of ~8:1, for intermittent use you can go from about 10 to 125HZ or 12:1.
In practice you will find the power at 12Hz is probably too low to do useful work so the practical range will be more like 25 to 125 Hz which is 6:1

There is a way to reduce the low power effect by purchasing a VECTOR VFD (VVFD).
These delivered considerably more (but not full) power at lower frequencies - but does not remove the motor heating problem.
There are two kinds of VVFD, sensor and sensorless. They cost a lot more and the sensor based units require extra wiring and fidling.
In practice I found that my lathe motor could deliver the same power at 12.5Hz with a sensorless VVFD as a regular VFD would deliver at 25Hz.

The use of a larger power motor means the power frequency problem is further reduced. If a 1HP motor can deliver 1/2 HP at 25Hz then using a 2HP motor will deliver 1HP at 25Hz.

So I'm looking at buying a new and bigger 3 phase motor ( 3HP which would be equivalent to 1.73HP on the VFD ) and a VFD along with a new pulley to fit the larger motor which in total will come to ~$500. Then i need to get an electrician to hook it all up.

Before you buy the VFD talk to an electrician. Not all VFDs are the same and he may not be comfortable with using the VFD you have purchased (after all he/she has to guarantee the work) and it will take time (hence money) for him/her to get up to speed with an non-familiar VFD as instruction manuals typically run to many dozens of pages e.g. my Honeywell VFD has 3 books running up to several hundred pages.

The VFD will then also be the ON/OFF switch - however I'm thinking I'd like some kind of Knee/foot operated switch, especially to turn it off incase of an emergency etc.

I would not recommend using the VFD as the ON off switch. The VFD should be protected from dust by placing it inside a vented enclosure OR placed away from dust.
This means it will not be (as easily) accessible as a nearby switch.
I recommend using a remote on/off switch and variable speed control.
Another reason for this is that switches on VFDs are usually too small and lack mechanical and visual positivity - you need to be able to see that the switch is on/off.

Here is my setup - this has a standard VFD set it My metal work lathe uses a sensorless VVFD.
On this WW lathe the VFD is on a stand attached to the bench above the head stock - ideally it would be even further away that this but my efficient dust extraction system means that it is relatively dust free in this position
The on off switch and the speed controls are on the white plastic box below the pulley cover.
There is also an emergency mushroom switch on the lathe stand at thigh level.
On mine this just cuts the power to the VFD but there even better ways of doing this especially as some VFDs still allow the motor to coast when the mains power is cut - this one doesn't do that

Thanks Bob. Looks like I have some more research to do! Not least of which is checking with my Electrician ( Have emailed him today ). I will definitely be getting a remote on/off switch......I do like the addition you have of the variable speed knob outside of the VFD unit too.......I'll save my questions about how to do that for another post!

This is the VFD I'm looking at: 2 2KW 3HP 10A 240V AC Single Phase Variable Frequency Drive Inverter VSD VFD | eBay
This is is the motor I was going to pair it up with: 2 2KW 3HP 1400rpm Shaft 28mm Electric Motor Three Phase 415V | eBay

The guy at Conon ( who i've spoken to on the phone, and has actually been quite informative and helpful ), said this combo would work, but now you have me thinking it might not because the motor is 415v 3phase, not 240v 3phase ( or atleast it won't work without noticeable power loss compared to a 240v 2phase equivalent ).

I'm not tooooo worried about power loss, so happy to get a slightly bigger motor to compensate if need be. As long as I can run a reasonable range of speeds......I'm not going to be turning any crazy big bowls or anything nuts that I'll need super slow speeds for anyway.

Originally Posted by Sebastiaan76

The guy at Conon ( who i've spoken to on the phone, and has actually been quite informative and helpful ), said this combo would work, but now you have me thinking it might not because the motor is 415v 3phase, not 240v 3phase ( or atleast it won't work without noticeable power loss compared to a 240v 2phase equivalent ).

I've purchased stuff from Conon and their stuff is basic but reliable enough. The one thing I don't trust is what their eBay web pictures say. Some of the pictures on one model link out to a different model with different RPM and HP.
Never the less, the link to the 1400 Rpm 3HP motor does link to a picture which when magnified shows this nameplate.

Motorplate.jpg
The info in the red circle almost certainly says that this is a 220V ∆ motor and 380V Y 3P motor.
If it runs on 220 V 3P it will also run 240 3P at full power.
AND
More importantly the conversion between the two can be performed by switching connectors inside the mains junction box on the outside of the motor.
This will take the sparky 30 seconds to perform.
BUT
I would not take the website picture as gospel and get the supplier to confirm in writing the at the motor is a 220V ∆ / 380V Y motor

I'm not tooooo worried about power loss, so happy to get a slightly bigger motor to compensate if need be. As long as I can run a reasonable range of speeds......I'm not going to be turning any crazy big bowls or anything nuts that I'll need super slow speeds for anyway.

Going from a 1HP to 3HP motor doesn't worry some folks but I would definitely worry about about it on a WW lathe.
The problem is that when the motor is a full power things can go from bad to disastrous faster than you can blink.
If something catches, instead of a bit of tear out and perhaps stalling the motor, the motor will tear any tool out of your hand and is liable to dislodge the workpiece and throw it fair across a room. It can also more easily break tool rests etc
The most I would go to is about 2HP - that will still run fine with a 3HP VFD and allows for a bit of leeway so the VFD isn't working so hard.

OK, yeah, will definitely check with the Electrician. Also, good to know that 3HP might be a bit of overkill..........so will look for a a 2HP setup ( which will also save some $$ ).

At any rate, here are some pics of the beast, which I hope is worth the effort! Anyone know what brand it looks like? p.s. note the Huon pine turning blank + unfinished Huon pine bowl they guy gave me as well! ( I'll wait until my skill improve before I have a go on that! ).
Edit: the lathe is 1100mm long bed


20160209_200418_resized.jpg20160209_200430_resized.jpg20160209_200441_resized.jpg20160209_200451_resized.jpg20160209_200507_resized.jpg20160209_200534_resized.jpg

The twin posted horizontal support for the outboard end looks very much like the same setup on Woodfast combination machine so I immediately thought it could be an old school Woodfast lathe.
I subsequently did an image search for Woodfast lathe and guess what turned up?
Wouldn't you know it, it is!


See Used Woodfast Heavy Duty Wood Lathe Woodfast Wood Lathes in Campbellfield, VIC Price: $1,500 <219217>

As you can see by the price it's well worth restoring.

The Cadet motor is a very common one from about the 1960s and there were very many of these made
I have a similar but 1/2HP unit on my Hercus MW lathe that I swapped for a 1HP unit.
I also have 1/4HP Cadet motor attached to a squirrel cage fan I found in a skip.
I converted the 1/4HP from Y to ∆ and that is running as shed air extractor for when I run my Forge

Yes, the two lathes look from the same family, and given i know mine came from a school, and Woodfast have a long history of supplying schools, I'd say it's likely that's the case.

Agreed I think it's worth restoring and fixing. It's super heavy cast iron bed, and with 2HP VFD it would be equivilant to a $2k+ lathe when restored in my opinion, and probably only cost $400 - $500 including some elbow grease and paint!

It's a shame you live so far away......I'd love to check out your workshop, it sounds awesome! (hint: feel free to post some pics of it ).

Originally Posted by Sebastiaan76

It's a shame you live so far away......I'd love to check out your workshop, it sounds awesome! (hint: feel free to post some pics of it ).

You want pics? well I have a 24 page thread dedicated to the fit out of my shed addition and reno of the old shed
BobL's shed fit.
There's quite a bit in there about VFDs being fitted to various machines.

OK Bob....I'll admit. there is a slight amount of envy upon seeing your shed! But great work!

Cheers

Seb

I picked up an ex school Woodfast the same as per Bob's pic in January, along with a slightly more recent mechanical variable speed unit from the same school. School had money to replace them and had their regular electrical maintenance people disconnect them in preparation for a scrappy coming to take them for nothing. School mentioned this to the sparky, then offered them to him free of charge if he could arrange to remove them that day. He had them in storage at home for a few months, planning to keep the belt change unit and move the varispeed one on. I found the varispeed unit on ebay and was the sole bidder. When arranging collection, he told me that he had the second and suggested a price for both that was well under what I offered for one varispeed three years ago, so I made sure I had enough cash to close the deal when I went to collect the one I had definitely bought. After looking at the second one, it took a whole three seconds to agree to buy both at his nominated price.
I have both in storage at the mo as I am currently shedless after moving house. Dismantled a 12x16 American barn and bought it with us, but cannot get approval to re-erect it until we start building the new house where we are moving to. One way for rural councils to stop people living in or running businesses from a shed on otherwise vacant land in a residential area. House should almost be finished this time next year, shed should be up end of November this year, have to wait till the stumps or slab for the house are completed before starting on the shed.

So Malb....the question then is.....do you need both?

You also raise an interesting point that I'd often wondered about - i.e. during my sometimes wistful desire to sell up in the city and move to the country I thought how I would go about building a house and living on the block whilst doing it....but it seems you couldn't just put up a shed and live there whilst building then. I wonder if you build a shed on a trailer, i.e. it was a trailer, not a shed, if you could live in that!