All that I would say is that 5 inverters would/could be cheaper than the rotary converter.

Cheaper to run, too – no auxiliary motor taking power all the time it is switched on.  No need to turn the power off to change direction, either.

There are lots of useful programming options with VFDs. Variable speed, soft start, braking, jogging, easy reversing, and others.

Having said that I’m not sure about the lathe. Most motors can be re-wired to run 240V three phase, but some machines have peculiar interlocks or dual speed motors, multiple contactors, etc. 400V VFDs tend to be expensive items.

The other option is for a vastly over-sized inverter, which could run all of the motors (without any programming options, of course).

I like my 5 VFDs. Virtually no current draw when idle. Suit my machines and all the ones I have bought have given no trouble. Hence I would not entertain a rotary converter for my hobby workshop.

Others will be along shortly, to differ with my opinion, I expect.

Edited By not done it yet on 14/03/2022 15:55:40

Robert

Given the current prices of name brand VFD boxes from the likes of Inverter Drive Supermarket (my go to) and other reputable suppliers the Transwave converter system is not really cost effective for your proposed use. In your situation as a non-electrical person the big win of a converter is that it is simply plug and play with no need for modifications to the machine electrics.

I'd set up permanent lines to the machines with an isolator in the way rather than swopping at the converter. Lets you put the converter out of earshot. The buzz of the internal motor and transformer can be obtrusive.

I suspect that if you have the set-up professionally installed and signed off you will need separate plugs and isolators anyway to meet current regulations. I like the yellow bodied with red lever control ISO isolators made by Lewden for this sort of thing. Not silly expensive and its obvious whether things are on or off, even from right across the workshop. Can be hard to find tho'

20 amp version here **LINK**

https://www.powerdiscount.co.uk/lewden-iso-20-isolator-20a-4-pole-ip56-59886-p.asp

Same thing under ERL brand **LINK**

https://www.electroreplacement.com/erl-4-pole-isolator-switch-20a-35a-45a-63a-max-415v-ip66

I absolutely don't approve of the round knob isolators because its hard to see if they are on or off from any distance.

If your motors are dual voltage and you can find affordable help with the wiring changes you will only need two inverters. The extra load of the suds pump and mill feed motor swill not worry a decent brand inverter. Especially if you don't exploit the speed changing capability of the VFD and simply use it as a 50 hz source.

That said most dual voltage suds pump motors work fine using the "capacitor trick" to run off single phase supply and its arguable that having a three phase feed motor tracking spindle speed makes life a little easier when milling. Most relatively modern feed motor systems use DC motors run off a transformer connected to one phase of the 3 phase supply which can easily be transferred to the normal single phase mains supply so no need to connect to the VFD anyway.

But you will need to find help if you are not confident with electrics.

Clive

There is a 3rd (4th?) option which is a digital phase converter. These have been discussed here so you should be able to find the thread. They work differently from an inverter because the mains itself is used to supply one phase, with some clever electronics to produce the other two. So the frequency is fixed at 50 Hz but I believe that they can be used as a "drop in" replacement for rotary phase converters (which are horrible in this day and age). Drives Direct i believe stock them for one and should be able to advise.

The plug and play digital phase converters sold by Drives Direct are an effective substitute for proper three phase mains supply. Mine is well over a decade old and doing just fine.

In principle nothing particularly clever about them. Just a normal style of single phase inverter with voltage doubling rectifier on the input. In practical the clever bit is making it work properly and seamlessly. Back in the day lots of folk offered voltage doubled inverters that sort of worked up to a point on E-Bay et al.

Not cheap. Price is similar to with Transwave converters of similar rating.

You can also get rather less costly Chinese made 380 volt nominal output inverters which should be able to run the lathe and mill motors without major wiring changes. Basically just bypass the existing controls and use the inverter buttons instead. They are said to work OK but I'm a little unconvinced as the suppliers seem to be E-Bay type "list and send" folks without proper technical back up.

Clive

In my house built 2 years ago, 3phase to the building was the same price as single phase to the building. With the high density housing going up around us, the electric supplier instructs the electricians which phase the house has if single phase, or if 3 phase, which phase is the kitchen. This is to lower the overall current on any one phase for their peak demands. The advantage for me was 3phase to the garage of course. Recently , older houses with the asbestos main boards, are being upgraded with new meters, and 3phase connections at no additional costs. The new connections put the oven, electric hob if separate, on their own phase, with the rest of the house on the other.

So it may check to see if any such upgrades are happening in your area at all.