To use 3 phase converter, or not to use 3 phase converter?

I will be purchasing a new 7.5 hp two stage air compressor. It will be used around a mostly automotive shop setting. Mostly being used with a good sized sand blast cabinet, usually they require cfm in the high teens.
I have used a 5 hp compressor before, but just could just not keep up. Unless you like running it 100 percent of the time for hours at a time.
So, my question is 71/2 hp compressors come in either single phase set ups or three phase set ups. With the three phase I would need to purchase something like an American Rotary for around 1200 dollars.
Is there any advantage in using the phase converter and three phase air compressor, over the single phase air compressor?
Any savings in efficiency, electricity cost, etc.?
There is a possibility of more three phase equipment coming later, but each machine will be used one at a time.
Also noticed that Quincy air compressors, while a few hundred more, are made in U.S.A. if you believe they are a good choice, I would prefer to buy American.
Thanks Todd

If you are going to add more machines later go with an RPC. I went with a PhaseCraft panel (he is a PM) member. The panel and a good used 7.5hp motor cost me about $250. Coming on 3 years and it's still running fine powering 5 3 phase machines in my small shop.

Power is power, as far as an air compressor is concerned. There is no big advantage to 3 phase, as there is on a lathe, for instance.

If that is the only three phase unit, I would go single phase for it. Why pay for three phase conversion if you get nothing much from it other than the opportunity to spend extra money?

Later, if you get 3 phase machines, you can obtain a suitable 3 phase converter, or use VFDs , at your choice. You can then get the converter suitable for the power levels of the machines.

Thank you both for your input. I have another room that houses my lathe, mill, and surface grinder. Was given to me years ago a phase o matic and for my use seems to be ok. For the garage application, sand blaster, was thinking there might be an energy savings, but I guess not.
Checked the Phase Craft site, and it looks like the basic 7.5 hp panel is now around 750.00. Perhaps I am looking at it wrong. For a few hundred would go three phase, for close to a thousand, including paying installation, will probably stick with single phase compressor.
Thanks again for your time. Hopefully get a couple more replies.
Todd

todd1 said:

I have used a 5 hp compressor before, but just could just not keep up. Unless you like running it 100 percent of the time for hours at a time.

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The volume of the storage tank, cut-in and cut-off pressures are more important factors than upping the hp by 2.5.

The key is sto look at pump displacement and rpm. The old Quincy QR series was among the best compressors made and can be had used pretty cheap. A larger pump running more slowly to acheive the need cfm is better than a smaller pump running fast. 600-700 rpm is ideal. A QR 350 running at 600 rpm is better than a 325 running over 900 for instance. A larger 100-120 gal tank is also better as the air has more time to cool down and drop condensation before it goes through the dryer. I've rebuilt a couple of Quincys and would take them over a new ( except their new QR which costs >5K ). Single vs three phase is only important if you need to run heavy wires which would offset the cost of vfd or rpc- either of which can be had reasonably now too. Dave