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three phase to single phase motor swap

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Dougie Swan01/06/2018 13:09:21
187 forum posts
40 photos


Apologies if this has been asked before but I did a search and got no results

I have a harisson m300 that until last week was powered by an inverter, I always new the day would come when it went pear shaped and so it came to pass

My question is this, can I swap the three phase motor for a single phase one, I have read that they dont like to be switched on and off a lot but I work with lots of different motors in catering equipment and they seem to cope with it ok

Has anyone any experience of this and if so can you give me some advice

A new inverter is probably out of the question as I just dont use the lathe as much as I used to and when I did it ran away with the power

Any advice would be greatly appreciated


Edited By Dougie Swan on 01/06/2018 13:10:09

Nick Hulme01/06/2018 13:23:30
743 forum posts
37 photos

M300 with a single phase motor?
Ha'p'orth of Tar?

Dougie Swan01/06/2018 13:26:04
187 forum posts
40 photos

What exactly does that mean?

Brian Sweeting01/06/2018 13:34:43
442 forum posts
1 photos

Looking at it seems the M300 did also come with a 230v single phase 1.1kW motor but due to the lower power the usable speeds drop by 50%.

not done it yet01/06/2018 13:50:26
4994 forum posts
20 photos

Less than a hundred quid for a cheap chinese VFD. Better ones are available.

Motors are generally rated by starts per unit time (usually per hour) but that may be modified dependent on whether starting off-load or under a load. Soft starts ameliorate this problem somewhat.

A 3 ph. motor is always preferable to a single phase for size/power ratio, quietness and smoothness in operation.

Electronic inverters are quite reasonably efficient and do not consume more than a couple of Watts, or so, when idle.

Firstly - are you sure the motor is good? Is it 230 or 415 volts? If 415, can it be simply wired for delta configuration or can the star point be easily split?

SillyOldDuffer01/06/2018 14:11:11
6313 forum posts
1382 photos

Nick means fitting a single-phase motor to an M300 will spoil a rather nice lathe. I agree - staying 3-phase is far more desirable if you can. A new VFD can be had for between £100 and £400 and even the cheap units can be programmed to 'stop it running away with power'. You can even get high-voltage units so you don't have to mess with star-delta, though they are more expensive.

Single phase motors have several disadvantages, stop-start beiing only one of them. They're not awful, just not very good. A tad inferior rather than useless.

In the last 20 years VFDs have made getting 3-phase easy. Now it's rare to convert a 3-phase machine to a single-phase motor. But the lathe will still work if that's what you want to do.


ChrisH01/06/2018 14:45:45
878 forum posts
29 photos

Dougie - the full phrase is along the lines of don't spoil the ship for a halfpenny's (pronounced ha'penny's) worth of tar. Goes back to the days of sailing ships where planks of wood were sealed against water ingress with tar.

Having just converted my mill/dill to 3ph motor with inverter control I quite agree with all the above comments saying get another inverter. Talk to Inverter Drive Supermarkets (no connection - just satisfied customer) and ask them to suggest an inverter to suit your existing motor - you may be surprised with the reasonable cost!


Dougie Swan01/06/2018 15:06:12
187 forum posts
40 photos

Thankyou for all the sensible replies/advice

I'm going to send me inverter back to drives direct to see if it can be repaired then take it from there

Thanks Again


john fletcher 101/06/2018 15:27:16
622 forum posts

Provided the windings can be re configured in Delta, your motor will be OK, this usually can be done in terminal box in a few minutes. Several of my friends have bought Huanyang inverters from Ebay for about £110, some came from Leicester others from Germany. All are happy with what they bought. Not sure about those £400 pound jobs, do we really need such sophistications for home workshop use. I wired my friend Harrison lathe using the original controls, he bought the bit from Maplin who are no long trading.The inverter on my lathe is at least 30 years and it keep on rolling along, it was second hand when I got it, off an discarded printing machine.One hears a lot about motor running hot when on slow speed, well I've check mine and nothing untoward has taken place so far. This maybe the case in industry , I have see motor with external blowers for cooling,I have one of those cheap laser type temperature guns via ebay it works well.Three phase motor are simpler than single, less moving parts consequentially are more reliable. if you buy a Huanyang I have simplified programming list which you can have a copy of by sending me a PM with your email address. I'm told there is a good DVD thing on YouTube showing programming a Huanyang inverter. John

Martin Johnson 101/06/2018 15:50:32
129 forum posts
1 photos

Aside from the basic horsepower question in replacing 3 phase with single phase, there are some other issues to consider:

Starting torque - not great with single phase, but very good with a 3 phase started directly on line. Spinning up the drive train, spindle, faceplate? etc. on a Harrison takes some grunt. Can be got round with a clutch, but maybe a VFD would be an easier route? The catering equipment you have seen started on single phase motors probably didn't have the mass of a Harrison to spin up?

Starts per hour - the high current at start up heats up the motor, so the more starts per hour you make, the hotter it gets. Can be significant when you are making a tricky component. You can either fit an oversize motor - go up at least one rating on the power, or try and find a specialist motor designed for such abuse (alternatively search for rocking horse poo).

Hope that explains some of the issues.


Bazyle01/06/2018 16:54:00
5462 forum posts
206 photos

The M300 is a 12in gear head lathe mostly equipped with 3 phase because the primary buyers were small industry and schools. However Warco and Chester have sold thousands and thousands of far eastern 12 in gearhead lathes with single phase motors for home use. They work ok. Just look at their specs to see what size motor they use.

Unlike an old plain bearing lathe with small motor that had to have its bearings warmed up in slow gear before the poor little motor could get them to go fast a gearhead uses thin oil (if some twerp hasn't filled it with EP90) so shouldn't have that problem.

If you have been using an inverter the motor is probably already set in delta configuration.

Ian S C02/06/2018 11:49:06
7468 forum posts
230 photos

My 13" belt head lathe has a 1,5hp single ph motor, and it struggles at times until warmed up, specially now in the winter, a rear head lathe of similar size would require at least 2hp to get any work done rather than just nibbling away.Stick with the 3ph if at all possible.

Ian S C

Zan04/06/2018 13:53:04
185 forum posts
13 photos

I converted my 3 phase Colchester to inverter run on 240 v the main control box which had to be rebuilt to contain the inverter needed 30 odd wires all needing to be correctly connected. You are considering going the other way. It's not just about the motor, all the control gear, contractors switches, pump etc may not work on 240 v. I agree with earlier comments, get a new inverter, a lot simpler and better in the long run.

Don't forget as well the inverter must not have any switch gear between it and the motor, if any are there the inverter is so easily destroyed. So in addition, these will all have to be provided and connected up safely along with any override emergency stops, so you will need contactors, all in all a big job.....

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