Thanks Julie
I already own the machine and I will be moving it from my workshop that has 3 phase to my home workshop that only has single phase. What I can gather from the replies is that to get 27A 3 phase I need to have a rotary inverter that needs an 81A single phase supply. There are other machines too that are lower power and only one will be used at a time.
I have several choices:
A few digital inverters for the low hp machines.
A larger rotary inverter for the larger machines.
A diesel generator to cover the lot.
Two smaller diesel generators that are wired together and use one or both.
A combination of any of the above.
You really need to check the ratings as I doubt the numbers you are using are correct, my husband has a 3 phase Harrison lathe at home in his workshop (+ Mill etc etc) this has a 1.8hp three phase motor and we run this via a 13A fcu (fused connection unit) through a rotary converter, if yours is 7.5hp - ~4 × the size of ours, then at most I would expect 4 x 13 or 52A in reality.
We have a boost energy systems unit, and it states that the boost 6 needs 40A fuses - I think that is 6hp
A single phase motor of 7.5 hp would have a flc of around 50A
Does it have an inverter fitted to the motor?
These run at a lower current than converters as they generally have the ability to remove apparent losses
(a motor has an efficiency, but also a "power factor" this means that although 10A is flowing, only 7.5A is effectively powering the motor - a power factor of 0.75 in this example, however an inverter directly on the motor could translate this to a pf of around 1 - so we actually would only need 7.5A in the supply cable with the inverter rather than 10A without)
This isn't necessarily the case if you use an inverter just to supply a fixed three phase supply.
Generally you would struggle to run a converter of 80A on a domestic supply.
Inverters are kinder to the supply than rotary converters, but some have a minimum load.
We had the same issue as you, one rotary converter for the whole workshop, convert each machine to single phase, add an inverter to each machine etc.
Husband likes the flexibility to just start the converter on no load, leave it running and start/stop machines just as if we had a proper 3 phase supply.
