Why are 3 phase motors with VFD so popular in the UK?

I see many posts and articles where people have fitted 3 phase/VFD to their machines. Yet I know of nobody here in Australia who has done this. It’s unheard of. There is a current post where the conversion has even been done to a drilling machine. Why the big difference when both countries have the same power supply? Is it fashion, marketing, or what?

I think it must be “or what”

The advantages are very obvious, and the cost is realistic in the U.K.

… I have just started restoring [well, cleaning-up] a small precision drill with a lovely 1/4 HP 3-phase motor … no way I would change it for single phase !

MichaelG.

Edited By Michael Gilligan on 20/01/2023 21:24:07

I have replaced the 1/2 hp single phase motor with a 1 hp three phase and VFD on the Tom Senior light vertical which the museum inherited. One reason was that the spindle was converted from MT2 to R8 and a bit more power would be useful. The motor speed control is a bonus, with a 6 pole motor running between 25 and 75 Hz, it runs between 450 and 1350 rpm giving the mill, which also has 4 speeds by belt, a good range. VFD's can be programmed to reverse the motor if required and also the acceleration and deceleration can be programmed. Also, a lot of 3 phase ex industrial manual machinery has come into hobby use and it is often easier and cheaper to dispense with the complicated 3 phase switchgear and run from domestic mains which is usually single phase. Three phase motors run smoother than single phase.

Edited By old mart on 20/01/2023 21:32:14

Edited By old mart on 20/01/2023 21:33:01

Not sure why you would say 3 phase/VSD is uncommon in Australia. It is a common topic on many (Aus) forums I visit. Often someone has purchased a used 415v 3 phase machine and wants to run it on 240v single phase at home. Sometimes they want the easy speed control or other features.

I agree. The only mistake I made was going for a 1/2HP motor instead of a bigger one, but hey ho.

I've converted all of my machinery (except a bandsaw) from single phase to three phase with VFD, once you've appreciated how adaptable and controllable they are after the conversion it's total no brainer.

Drilling machine - instant adjustment of speed over at least 5:1 range (20 Hz to 100 Hz no problem). Can set the speed for a 3 mm pilot hole and then lower it to open the hole to 13 mm drill at the twist of a knob, no need for changing belts. Controlled soft start, DC braked stop (legal requirement in commercial usage in UK), and reversible with programmable ramp down/ramp up acceleration for tapping, left hand drills etc. No consideration of number of starts or capacitor life, no centrifugal switches to fail. Single phase motor can be reversed but you have to wait for it to come to a stop before applying power again. No such delay with VFD, the speed profile just follows the pre-programmed parameters.

Milling machine - all of the above plus wider speed range to take advantage of carbide tooling. Extend speed range downwards for face mill or side and face cutters, also as another tool in the box for controlling vibration. Switchable low speed range for set up (e.g. wiggler usage)

Geared Head Lathe - all of the above, particularly the soft start and braked stop (no the chuck doesn't screw on!) Being able to extend the speed range downwards is particularly good when working on large diameter faceplate work with the gap bed out.

Myford S7 lathe - can't have braked stop 'cos the chuck might come off, but otherwise the same as above. Also advantageous when metric threading (imperial leadscrew) to be able to program reverse speed (back to start) at twice or three times forward speed.

Try it, you're missing out!

PS (edited).  Motor start doesn't knock a ruddy great hole in the domestic mains, so SWMBO can keep watching Eastenders (spit!)

Bump DOL reverse start with a screwed on chuck is asking for trouble, whereas programmable soft start with VFD solves this problem.

Edited By Simon Williams 3 on 20/01/2023 22:49:03

I have seen a lot of modelers install VFD's in their shop.

They seem to be popular here (US) too.

I have resisted using these devices so far, although I could use one on a hacksaw I purchased that has a 3-phase motor.

The reason I don't use these is as follows:

1. I am concerned about the long-term reliability of the electronics.

2. I am concerned about the spikes that VFD's can put on the input and output, which in turn spikes the motor windings and motor cable, which can cause both to fail over time.

3. I am old-school, and I prefer to use as few electronics as possible in the shop.

Some folks have said that given the small horsepower involved, and the limited usage of hobby shop equipment, the reliability and spike issue is not a problem.

I have specified industrial VFDs for many years, and I use an input inductor to prevent line spiking, and an output filter to prevent motor winding and cable spiking.

Industrial VFDs will indeed ruin your system if you don't watch out for the input/output spikes.

Some new motors are "VFD-rated", but most motors I see are not rated for VFD service.

I don't see VFDs in the hobby going away.

As many have mentioned, they are just too convenient (when they work).

It is similar to how my dad used mechanical dials/readouts on all of his shop equipment, and would not use a digital readout on anything to save his life.

I use digital (electronic with LCD screen) vernier calipers for all sorts of things in the shop, and I would not do shop work without them. I use digital vernier calipers as poor-man's DRO's on the lathe and mill, with great succes and very low cost.

My dad straddled the line with some of his micrometers, which had mechanical digital readout, like the old rotating drum clocks, where the drum rotates to different digits.

My dad swore off all things electronic and computer.

I am not able to avoid computers and such, but so far I don't have any VFDs.

I did buy a nice little kiln controller with SCRs.

Some times you just need and want electronic controls.

I do envy those who have nice DRO on the lathe.

I have to spread my hobby money across foundry and shop machinery, and so I have to be selective about which luxuries I buy.

.

Edited By PatJ on 20/01/2023 23:16:54

All of the advantages I appreciate, but that still doesn’t explain why no one in the ME community that I know of has a single such conversion. Prolific loco builders I know have ordinary, single phase lathes and mills. Chinese geared head 6” lathes are common but there are many with Myford and Hercus belt driven lathes. I’m not sure what forums Jon Holmes was referring to. I frequent only this and MECH. Could it be that model builders just get on with it, whereas many, especially here on ME Forum, are primarily machinery enthusiasts, who like to “hot up” their machines for its own sake?
Two members, long deceased, had a three phase supply to the house for ex-industrial machines.

Perhaps people in the antipodes really are years behind the times! Dons crash helmet and prepares to take the flak, and the dog out for a walk. Only joking, honest.

The advantages are only obvious if you have' the knowledge' Michael.

Always keen to learn.

Please could you or someone else briefly explain the advantages of three phase?

I can at least grasp the advantages of VFD~ also applicable to single phase i believe.

Extremely sketchy on three phase, was not well covered in science lessons way back when.

From what i recall domestic mains is one phase of the three phase supply @ the sub station ?

Why would my dril press work better on 3 phase?

Thanks.

Hi Simon

I think I must be one of those secret squirrel model engineers that are lurking about in darkest Australia.

I have three phase and VFD on my ML7 ( Newton Tesla ) plus a number of other sets planned for installation on other small machines.

On the ML7 the advantages are very smooth operation and variable speed control ( within reason ).

Why is it less common in Australia? - I think possibly it is due to the cost ( high ) and availability ( low ) of small three phase motors. VFDs on the other hand are reasonably inexpensive ex China and not to expensive to ship. Cost for importing a motor on the other hand can easily exceed the cost of the motor.

Oddly I suspect the motors may be available locally, just very hard to find ( It's a small market . The motor for my ML7 was purchased locally some years ago but whether the firm is still operating or making small motors I am not sure.

I have also contemplated changing my big 3 phase machines to VFD operation for the same reason as with the ML7 - i.e. smother operation and some greater flexibility in control. In these cases the the motor stays the same and the VFD is three phase in and three phase out. Again these VFDs are quite reasonably priced for fairly large motors, 7.5 HP in,my case.

Is it essential - NO. Is it nice to have - YES. Will the machine do the same things as it did before - YES.

Is it worthwhile - QUESTIONABLE. Only the individual can decide.

Pero

.

Sorry, this will have to be brief … I’ve just had my sleep disturbed at 04:00 and need to get back to the land of nod.

The fundamental advantage [on which all the others depend] is that 3-phase is smoother

… like comparing a single cylinder motorcycle with a Triumph Triple

MichaelG..

I think it is the cost factor here in Australia for good quality VFDs and motors. Cheapos are available from China but quality is ahem variable.

In the UK you can buy an already set up VFD and motor for Myford for way less than it costs to buy the same quality components here in Oz and set it all up yourself. When stuff is cheap and easy , people will do it.

Personally I haven't felt the need. Using carbide tooling I leave the Myford in top speed belt setting almost all the time and on the odd occasion I have to change it or engage back gear, so what? 30 seconds lost. Smoothness of three phase is nice but not something I feel the need to pay good money for. Heavy steel bench firmly bolted down and to the wall and carefully balanced pulleys is good enough for me.

It is a mystery to me why anyone would feel the need to be constantly adjusting the speed of a drill press. I leave it on about the 800rpm belt setting for 90 per cent of work that I do, drilling one or two holes in steel or aluminium from about 1/8" to 1/2" diameter. Changing the belt on the odd occasion to drill a tiny hole or a very big hole, well another whole 30 seconds wasted.

I am sure many others are the same. I guess in Australia living with the isolation, high import costs of a small market and the time delay to buy things and have them delivered, there is more of a tradition of just making do with what you have rather than regularly buying new toys to be delivered next day. But that is changing rapidly as internet shopping becomes more the norm so I expect we shall catch up in short order.

I’ve just done a bit of googling and there isn’t much at all in Australia. One mob has a motor for about $400, and VFD for $1000. For comparison I spent $300 on my very clean original ML7 and zero on my beautiful ARL Hercus. The main machinery warehouse for hobbyists, Hare & Forbes, don’t mention them on their site. Had they been displaying and demonstrating them on their big sale days, they might be more common. So in that sense, it is marketing, or the lack thereof. Like Hopper, I’ve never felt the need.

LOL. Except it is not a joke. When I moved back here after living longterm in the USA it was like a journey back in time. It took me several years to gear down to local speed. Which is not necessarily a bad thing. But it did take some getting used to.

Is it to do with the availability of second hand 3-phase machines being a lot more abundant in the UK than down under?

Interesting that you say that Chinese geared head lathes are common, over here I would say those working with that size machine are more likely to be using Harrisons and Colchesters so all come with 3-phase and need a way to run of household single.

Conversions are not just the domain of old machines either. What about the benchtop machines that have fried a DC motor or control board. These don't have any belts or gears to change speeds so it needs to be done with the motor and a 3ph and VFD is the simple solution as well as probably costing less than replacement parts.

The drill conversion is an interesting one and where having the variable speed that a VFD provides will actually allow the user to get on with building faster. Lets take drilling a reasonable size hole, pilot at a high speed, enlarge at a mid speed and deburr/CSK at a slow speed. You could make two belt changes or just turn the pot which is a lot faster and allows you to get on with the actual build. even more advantage if there are multiple such holes to be done

Edited By JasonB on 21/01/2023 07:58:26

Or you can do what I do and run the drill press at circa 800rpm - 900rpm and use that for your pilot hole, larger hole and deburring. No need to change speeds every time you change drill size. Drill speed charts are optimum speeds for industry to balance metal removal rate with tool life. As long as you don't run too fast and burn the cutting edges, or too slow on sub-1/8" drills and snap them, one speed will do 90 per cent of the work we do. Changing speed every time you change drill size is overkill.  I go for months at a time without changing speed.

If I am working on a small model project where I am repeatedly drilling small holes, say tapping holes for 1.5mm or 2mm threads etc, then I will change to a higher speed for the small drills, and use that speed whether I am using a 1mm bit or a 2mm bit etc. Then when I go back to working on motorbike stuff, all 1/4 to 1/2" holes, i change the belts once to 800rpm or so and leave it a that.

Colchesters and Harrisons are rare in Australia. And what there are have been worked to death in professional environments for the most part. And those mid-sized Chinese gear head lathes say 13" swing by 30" long are widely sold and cost about $3,000 (1500 Quid) so they are popular. Pretty good lathes for the most part other than the noisy steel gears in them. The earlier belt drive models run quieter. They mostly come with 1 phase motors.

Edited By Hopper on 21/01/2023 08:18:43

Basics, for Samuel and anyone else who may be wondering:

**LINK**

https://youtu.be/4oRT7PoXSS0

MichaelG.

Smoother running and better control was a good reason to modify my machines (3 lathes and a mill), but another reason was the cost of repairing the original motors/electronics. I did repair the control unit on one lathe myself successfully a couple of times, but it failed again later, and also the DC motor. After looking up the cost of replacement, or the rip-off prices charged to get them repaired, with no guarantees, it was cheaper to buy VFDs and new 3-phase motors, both of which were easy to source from many suppliers, whereas the original parts (in some cases) came from one or two suppliers. Sure, I had to make some modifications to fit different motors, but nothing complicated, and it meant the mill got converted from gear to belt drive - far quieter and smoother running.

In reply to the comments about electronics reliability, it depends what you mean by reliability - you only have to look at this forum to see the number of times the original electronics fails on Chinese lathes. Sure, a lot of VFDs are Chinese made as well, but at least they can be purchased for a reasonable price, unlike the lathe and mill controllers, and I have never had problems with the ones I have.

That said, I for one have had no troubles with my VFDs after doing the conversion, and the machines are much more useable - soft starts, smoother running, speed control, reversible, remote control - the advantages easily outweigh the disadvantages in my opinion.

.

Whether your drill press would work noticeably better on 3 phase will depend on the machine and on your ‘use case’ … but I’m confident that mine will

.

.

It should just need the links swapping to Delta connection and will then run from a small inverter/VFD

… it would be a pity to waste a good little motor like that

.

MichaelG.

Edited By Michael Gilligan on 21/01/2023 08:32:19