Which phase converter

[Muskymoto]

I have a Boxford lathe as pictured below ( if picture doesn't work follow link its the 3Rd lathe down the page)

http://www.lathes.co.uk/boxfordmodern/img2.jpg

http://www.lathes.co.uk/boxfordmodern/

It is a 3 phase machine and I would like to be able run it on single phase but still be able to run all the machines functions i.e turn coolant on and of and reverse the motor but without flicking the phase converter on and off

So what im after is a 3 phase inverter that will just supply live into the machine and be able to turn the machine on and off via its controls on the headstock

Im no sure which phase converter to use i.e A rotary one a Digital one or a static one?

Any help much appreciated
Regards

Marcus

 

[JorgensenSteam]

What are typical voltages and frequency where you live?

What is the voltage, horsepower of the lathe motor?

 

[Muskymoto]

50 hz 240v single phase i do believe

 

[JorgensenSteam]

I generally like to operate motors that are above 3/4 hp at 240 volts.

My mill operates at 1.5 hp, 1-phase, 120 volts, but that is a stretch for 120 volts. I get away with that because the motor generally is lightly loaded. If I make a large cut, or use high rpm, the breaker trips.
If I had purchased my mill originally, I would have used 240 volt, 1-phase.

For your 3-phase motor, you will need to find a converter that is rated for the 3-phase motor horsepower you have. Read the converter instructions carefully, as some converters require a derating, for example, if you are operating a 2 hp, 3-phase motor, the converter manufacturer may recommend a 5 hp converter.

I would recommend a 240 volt, 1-phase input unless your motor is 3/4 hp or less. 240 volts requires a two-pole circuit breaker, or two fuses, but generally the current is half for a given motor horsepower as compared to operating it at 120 volt input.

Both the rotary and solid state units work well.
I would find a supplier of converters that are readily available where you are, and then zero in on the exact size converter for your motor horsepower.

I would look at cost and availability, and pick the cheapest method that does what you want. Again, you need to match the input voltage and frequency that you want to use, match the motor voltage and phase on the output, and size the converter per the manufactuer's reccomendation (there is generally a sizing chart from the manufacturer).

 

[rhankey]

If you do not want to rewire or alter the controls of your lathe, then you want a rotary phase converter which will convert your single phase 240V house wiring into 3 phase wiring that you can supply to your lathe. Rotary phase converters use a motor to generate or “manufacture” the third hot wire. Should you need to, you can run more than one 3 phase machine from a single rotary phase converter, sizing the converter for the largest machine you have. You simply power up the phase converter, then use the downstream 3 phase machines as you wish, and when done for the day, you power off the phase converter.

The main thing to watch with rotary phase converters is to only use the "manufactured" hot wire to power 3 phase motors. If the lathe has any single phase 120V or 220V components, like lights, transformers coolant pumps, be sure to attach the manufactured phase to the terminal block of the machine to which none of these items draw their power. Even if you don’t have a wiring diagram, it is usually pretty quick and easy to figure out what hot wire the machine uses for any 120V/240V single phase items. If you find the main spindle motor runs backwards, you simply swap the other two hot wires around, leaving the manufactured hot wire alone.

As for company and sizing, I probably can't help you as you appear to be on the other side of the pond than me. If your local rotary phase converter suppliers work the similarly to those here, I would suggest you simply phone them and tell them what you have and what you may get in the future, and let them tell you what you need. They usually specify a larger phase converter for lathes than they do for mills, even if both have the same size motors, and depending on the approximate age of the motor, they may alter the specs too. As I mentioned, you can run more than one 3 phase machine simultaneously from one converter, so long as the phase converter is sized sufficiently for the largest machine.

Robin

 

[Muskymoto]

ahh great

yes im in England the biggest phase converter company here is Transwave so il give them a bell and see what they say.

I think from what your saying is I can run the coolant pump and the main motor at the same time with the correct phase converter so long as the terminals are the correct way?

oh and of the top of my head I think the motor is two or three horsepower

Cheers
Marcus

 

[RonGinger]

I would never use a rotary phase convertor again. Now that VFDs are relatively cheap, often even less than a rotary, why use a rotary? The VFD will give you variable speed, controlled start up and spin down and will not make any noise while its not running the motor- a rotary will drive you nuts listening to it run. Unless you move it outside, then you have issue with wire runs and weather proofing.

I suspect the VFD will also use less power.

You can wire the VFD to the stasrt/stop buttons on your machine. Thats all low voltage wiring and easy to do. You will have to re-wire the pumps and any other device to be separately powered.

 

[JorgensenSteam]

The only drawback to solid state equipment like VFD's and softstarters is that they do not tolerate surges/spikes very well at all.

Even a static electricity discharge to the controls can zap them.

My biggest problem in industry is VFD failure due to surges/spikes caused by distant lightning strikes to the power lines. I have to specify extensive surge suppression on industrial drives in order for them to last.

A rotary converter will most likely run forever, and will generally tolerate all sorts of power problems, just as a typical motor will.

Both devices have pro's and con's.

 

[RonGinger]

The only drawback to solid state equipment like VFD's and softstarters is that they do not tolerate surges/spikes very well at all.

Even a static electricity discharge to the controls can zap them.

I am surprised at that. I have 4 of them, one for more than 10 years, and many of my friends have one or more, and I have never heard of anyone having a failure. I suppose in an industrial site it may be different, but that certainly does not seem to be the case in home shops.

 

[Swede]

I've run two Hitachi VFD's for over a decade with zero problems. Adding a VFD to a gear head or especially step pulley machine is great... you set the machine's gearing or belts for a mid-range speed (or wherever you work most), and let the VFD do its thing. It'll deliver plenty of torque at low speeds. Kill two birds with one stone - get your 3P power AND dial-a-speed to boot. Being able to dial the spindle up or down on the fly, while cutting, is a very nice feature.

Reversing - no problem, most VFD's either have a reverse built in, or a switch can be attached and the direction controlled via the external device.

As far as the coolant pump, the benefits the VFD give are (IMO) worth the effort to rewire the pump system so as to work on 1P power. Whatever you do, good luck with it.

 

[n4zou]

TORQ provides kits for self starting any 3-phase motor on single phase power so it can be used as a rotary phase converter. Surplus/salvage 3-phase motors can be obtained at near give away prices. The cost to retrieve the copper in the motor is higher than the copper would bring as scrap and scrap yards will not take them if the copper is not removed. With a little scrounging you can obtain an old 3-phase motor and build a rotary phase converter on the cheap.

http://www.torq.com/phaseconverters.htm

 

[Swifty]

I run my Bridgeport and lathe using a rotary phase converter, never had any issues at all with it, although it is a bit noisy and very heavy.

From what I am reading from other posts, you use the VFD to switch the machine off and on. Just want to know what happens when threading on the lathe, coming to a dead stop and reversing leaving the half nuts engaged. This is easy to achieve using a foot brake and reversing the lathe not having to move from the machine. Or have I got the wrong idea.

Paul.