In view of my cack-handed wrecking of my S7 motor (see separate thread), I am looking at a potential excuse to spend some cash on a 3-phase motor and inverter drive. Always liked the potential for speed control, good torque at low speeds, smoother running etc and was toying with such an upgrade anyway.
I have looked at the advertisers in ME; I quite liked the look of the Newton Tesla package for the S7. Anyone out there got any comments on these or other competing versions? Do I need the 1 HP or will the 1/2 HP do? (The price difference is pretty small so I'd instinctively go for the 1 HP). Anything else I need to think about?
I would suggest seeing what young master Oseman has got for 1hp invertors on Charles&John's site and Ebay for a 3/4hp 4 pole motor. rswww.com for switches and variable resistor. The Newton Tesla drives are expensive bulky and ugly IMHO.
Hi I've just replaced the motor on my ML7 for a 3/4HP x 3phase motor and 1HP
1-3 phase inverter. It runs very well with verylittle vibration. Speed control is almost infinite through the remote control. Be careful to set all parameters on the inverter before use though, to limit top end speed etc. May I suggest Drives Direct for the motor and inverter package. Both of mine are new units and cost me £145 for both !!!! They can be contacted on
01773 811038. Back-up is brilliant with all the advice you will ever need. No, I have no connection to them apart from being a satisfied customer. Cheers Brad.
Alternatively to Marks suggestion of getting a second hand one you can get a new one rated at 0.55Kw or 3/4 hp from RS for £101 plus vat with warranty. Go to rswww.com and type in 431-9178 and this will bring up a 0.55Kw inverter that will run a 3/4 Hp 3~ motor that is more than enough for a S7. Their cost is £101 plus VAT and this is all in with programmer and filters A standard motor will cost you about £70 new or ?? S/H
Add to this a pot for speed control at £3 and a couple of start stop buttons and you are well away.
I have fitted literally 100's of these in the last few years and they are good units.
John S.
Apologies for posting via the RC groups but since Virgin altered all the web servers I can read URME but can't post to it via Agent.
I happen to have a S7 with the 1hp Newton Tesla package and to be honest I can't fault it. The drive is much smoother and quieter than the original motor and the variable speed extremely useful. Is it essential, no of course not but it is a pleasure to use and when you have the function available then of course you use it, extensively :-))
Is it worth the price? I really can't comment on that as mine came fitted to the lathe. I will say though that as soon as time and finance allows I will convert my other lathes to the 3 phase/VFD system; it is that enjoyable to use. One of the advantages of the NT system is that the motor is a direct replacement for the single phase one and doesn't need any messing with mounting/drive arrangements/pulley size - just bolt it on, plug in and go. The required parameters are already set up for you.
I guess like always "you pays yer money,,,,,,,,,,,,,,," In short, the Newton Tesla system I have is superb with excellent back up but only you can decide if it is worth your money. Not being in any way, an electrician, the long guarantee is also "comfortable" for me, my hobby is turning not wiring and chasing magic smoke!
While initially reluctant to take the plunge (see some of my past posts) after extensive advice from here I would not hesitate now to either buy from Newton Tesla or to put a similar system together. I am confident it would be a major improvement over the single phase setup. Yes, as always, I could save money (a fair bit as John has shown) over the NT setup if I want to do some of the work and take the trouble (and I guess a little of the risk) to find out how to set it up and make it work. Being "tight" and "lazy" (in that order), I think for multiple machines I will "mix and match" but, had I only one to do then the pocket might well be raided.
Thanks for the very helpful reply. Of course, the very different (but also very helpful) reply from John S pints in a different direction. As always, the decision is mine, and (as so often in NGs as in life) I am no wiser but considerably better informed....
Like many people I've fitted inverters to a number of bits of kit and think they''re great. I've even fitted one to a Super 7 with forward, reverse and speed control so do ask any questions. I seem to remember that you're not too far from where Andrew Mawson used to live. I'm in that part of the world at least twice a week on business and can drop round to offer help if needed. I'm sure it'll beat Starbucks in the town centre for a coffee.
My mill still needs an inverter but a 7.5 HP 440v in/out one is slightly harder to find cheaply!
I work at home most weeks, so you'd be welcome to drop round for coffee in any case. E-mail me offline (david at dlittlewood dot co dot uk) to arrange & get address.
I would agree with that...I fitted one of the early N-T drives to my ML-7 a few years back. It works fine, but is pricey for what it is. If I knew then what I know now I would have gone the route that John S suggests; you can also pick up drives on the 'Bay from time to time for even less. The one plus side for the N-T setup is that you don't have to think about it - bolt it on, plug it in, and it works.
I got a 'only just' used 3kW Omron inverter from fleaBay for about £75 I think and was amazed firstly how small it is - about a 6" cube. So far (after about a year) it's been no trouble at all and the programming's not a major headache once you read the book. I've arranged it as a sort of 'power pack' so I can move it from machine to machine in a few seconds. (Lathe, mill, bandsaw, pillar drill) They're all wired the same with standard 3~ plugs and my own 'standard' control connection (5way DIN).
As with most inverters it is easy to arrange to use the existing machine control contacts to control the inverter using what they describe as '3-wire' connection - do NOT switch the mains supply to the inverter from the machine contactor. I don't bother with the reverse or variable speed, but it does have a speed pot already on the front panel if I want it.
I'm just not keen on the great big boxes sticking out to catch you as you walk past.
Here are my first and second ML7s:-
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On the first one, the Dewhurst reversing switch was used as an isolator and for the forward/reverse control. The second one doesn't have a built in isolator.
You wont be able to use it for reversing and there is really no need to use it as an NVR either as the inverter should provide that function. Provided that the supply to the inverter goes through some form of isolator eg 13 amp plug then discard the myford starter. If you have the drum type switch, then these can usually be run from the control side of the inverter all at low voltage to give fwd - stop - reverse functions. However many inverters have a keypad that provide this functionality. Wait and see which inverter you get and then decide.
Quite agree, and have the bruises to prove it. However, I solved the problem for my S7 by putting the contactor box (which as it happens is slightly larger than the NT one) at the side, headstock end. It's perfectly accessible, helped by the fact that the stop button is at the right hand end of the box though....
Sounds sensible, Bob. Looking at the Drives Direct leaflet on installation (a download from their website) their external switches look very similar to a subset of my box, but I can see others have built in switches.
If you don't have the basic Electrical knowledge to fit the inverter, set the parameters on the VFD (Inverters) and wire the controls with appropriate interlocks (or have someone who can to advise you), go the Newton-Tesla route. A little expensive but safe.
Gavin O or E-bay units are often older models of VFD and you may not be able to get the instructions allowing you to set it up (change the parameters). Previously owned usually means limited (sometimes no) gurantee. I don't think the prices are always low either. You need to gave a good "feel for the deal"
Drives-direct do some good "packages" and, judging by their adds in ME/ MEW, have "moved up on the supplier ladder". They certainly advertise assistance and control systems. Again, may not be as low priced as other routes - but you'll have "on-line help".
Finally, the RS route is a good bet - assuming you have the basic Electrical knowledge (or access to someone who does). Bear in mind that you'll need a gew more bits and - as RS supplies to the trade - you'll get lottle back-up and you'll need a "trade account" with them. Maplin don't sell VFDs.
Just remember, if you can blow a single-phase motor it's even easier to blow your 3-phase ditto and a VFD if you don't know what you're doing.
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