Views on what is the best way forward

[normspanners]

I have a large compressor pump that I am going to drive off single phase I have a large 1ph motor off a large ind steamer/power wash not sure of the kw cause I cant see the plate but I would guess 2.5 ish .
Obviously the gearing will have to worked out, as I want the pump to run fairly slowly to keep the noise down.
I also have a large 4-5 kw 3ph motor and an inverter speed controller.
I was thinking of running the compressor unloaded up to speed before the load cuts in, and to do the main filling with the pump on two cylinders, then swap the pump onto one cylinder at a predetermined current load, to do the final high pressure pumping , to get it to 11 bar ish, without incurring high hp pumping current.
My question is, what is best a 3ph on an inverter, ramped to save on massive inrush or a large 1ph dol as such.
What would be the most efficient method ? are the inverters quite effiecient /cost effective for long term use.

 

[rtbcomp]

Would you gain anything by switching to one cylinder? You'd still require the same peak torque but only once a revolution instead of twice.

 

[Rig Pig]

An inverter will reduce the load on start up, we use them on some massive 185 kva electric motors that would just kill the generators if you tried to star delta them. Unloading cylinders may help but you will still have friction from the moving parts, wouldn't an engine and unloaders be better for high output and a small single phase pump for low output and maintaining pressure?

 

[normspanners]

You'd still require the same peak torque but only once a revolution instead of twice.

Not exactly as the flywheel effect would help carry the piston over tdc allowing the mass to accelerate inbetween and store energy for the next single compression.
I have done this before and it considerably reduced the power (current ) used by the motor at the point of unloading the one cyl, allowing the pressure limit ( limited by current draw) to be raised to a much higher point.
It means that the machine is simpler and quieter also I do not have to have two pumps and motors and the associated control gear etc.