... So, your point that the current draw has to be multiplied by 1.732 kind of makes my goal of reducing consumption by dialing down the fan a counterproductive effort, correct? (By the way, it does happen to be a 10a motor on the fan).
So, where rons recommends a surplus commercial 3ph. in / 3 ph. out VFD, will I get around the consumption issue? I'm a business, not a hobbyist, and my shop has 3 ph. service in place already. I'm not trying to generate it, I'm just trying to manipulate my fan. Is obtaining one of these units the logical way to go for my application?
You pay for POWER, not current. Current is a component of power, but power is power is power, you cannot alter that fact. So you have a 10A 230V 3 phase motor, that must be 3HP. 3HP = 2.24kW of POWER. Regardless of how you get there, you are going to pay for that 2.24kW of power, it could be 17A at 230V single phase, 10A at 230V 3 phase or 170A at 24V single phase, it all comes out the same (I'm leaving out a lot of math to keep it simple). Feeding it with single phase or 3 phase will make absolutely no difference in your POWER consumption.
A VFD only saves energy with a fan in one way. IF you can take advantage of a reduction in flow of your air delivery, AND you were doing it with a VAV box (Variable Air Volume), such as dampers, THEN if you remove the dampers and use the VFD to slow the motor down, it will use less energy because you have removed the losses in the turbulence created by the dampers. That's it, despite all the hogwash people spew about saving incredible amounts of energy with VFDs, it ONLY saves in that specific situation. Now mind you if you were using dampers and you run a lot, it does add up to a lot of energy. Usually a VFD in that situation can pay for itself in 18 months or so. But if you run the fan at a constant flow all the time, the VFD is going to WASTE more energy compared to just fixing any inefficiency in your system.
That inefficiency might be the result of an engineer being sloppy and saying "I could do it with 2HP but a 3HP motor will mean I don't get called back, so put in a 3HP". That happens a lot. In that case you could put in a VFD and dial the flow back to the equivalent of 2HP, saving you energy. But you would save MORE energy by just putting in a 2HP fan.
I know it's probably not what some VFD salesman told you, but it's the truth. I used to sell VFDs, I can attest to the fact that most salesmen have no clue about these issues, they are drinking the kool-aid and they pass it on.