I fitted my ML7 with a Newton-Tesla set, which is electronics plus motor.
My version is just a straight swap plus finding a suitable location for the inverter/controller. If you tell them the machine they know which electronics to pair with which motor.
I say "my version" – I'll go by that to start with. You'll see why, shortly.
The lead from the motor has a special plug for the connector on the electronics.
The main lead is rather short, at least on mine, so I have to use a short distribution-board. That though is a matter of workshop geography so may not apply to yours.
I placed the inverter on the cabinet below the headstock, but that is in the way of oil and swarf so I made it a cheap-and-cheerful plywood shelter that sits in the chip-tray above it. It's there because although I am right-handed, the disposition of the controls is better for using left-handed on the inverter I have. In particular, reducing the risk of accidentally using the wrong Stop button.
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I stressed that clause because the Newton-Tesla systems I subsequently bought for my other machines differ, by having two separate electronics units. Those do need more wiring – not difficult if you are reasonably happy with such work; but it is vital you put the right wire in the right place, of the mains lead and of the cable linking the inverter itself to the control "pendant". Which isn't really a pendant but a box with lugs for screwing it to a surface.
If the set you buy is of that pattern, put the inverter somewhere well out of the way of swarf and oil-spray, as it is not fully-enclosed.
That on my Harrison lathe is high on the wall above the tail end of the bed, with the controller just below it, still well clear of the muck. It also keeps me clear of rotating things – which can't be said for the rather dubiously-designed clutch lever a feature of the L5! Similarly with the set on a BCA JIg-borer – on the wall a bit above and in front of my shoulder when sitting at the machine. The set destined for the milling-machine will also be similarly elevated to a higher plane.
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One thing to watch (having just given myself an expensive repair!)…..
If the motor is the type with open ventilation holes in its ends, fit a shield to protect it from swarf, unless your lathe already has that luxury. Turning some bronze, most of the swarf "corkscrews" were falling harmlessly to the front, and I failed to see one sneak round the rather inadequate shield, and enter the motor. The resulting short to earth did not hurt the motor but damaged the inverter. I can say N-T's repair service is prompt, but obviously equipment like this is not cheap!
While the motor and inverter were away I fabricated a complete back-panel and motor shield – I've put a photo of it on the "What I Did Today" thread.
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Right…
Advantages? There are three, really.
– Very much smoother and quieter running than with the single-phase motor, which tends to make the cabinet (standard Myford one) resonate.
– Better speed control, especially for operations like screw-cutting up to a shoulder. By still using the back-gear, you can have everything moving at a less nerve-wracking rate.
– Ability to adjust the speed during the cut, as sometimes useful such as when noise or chatter may indicate wrong speed for the other conditions. Also when paring-off large diameters.
NB: 1. These motors do not like being run too slowly, and the warning colours on the speed control are for low as well as excessive speed. (Used in conjunction with the headstock gears, I can run the Harrison at about 60rpm with the motor still happy at nearly 1000 rpm.)
NB 2: Don't use the Emergency stop-button as normal stop. The makers warn its frequent use can harm the electronics.
Disadvantages?
I've not found any.
So, I hope this answers your query!