For the last two nights, I moved the compressor into the garage and have been trying to find a good way to run it. This is a Quincy compressor with a 5-10 HP rated pressure lubricated pump.
The compressor is now powered by a 10 HP Reliance motor that I had in NOS condition. I reused the old pulley, which I had to bore out, but with this pulley it only produced 7.5 HP of output since the pulley and RPM stayed the same.
Installation of the motor is shown here:
2) Quiet starts3) Being able to vary speed a little bit, so as to either run super quietly when I do not need much air, which is the usual case, or in case of high demand to use full 10 HP at higher speed. According to my simple calculations, it would run at 5 HP output at 40 Hz, 7.5 HP at 60 Hz, and at 10 HP output at 80 Hz. (the top limit is a little more iffy, but should be close at pressures lower than 145 PSI)
I used the following VFD: Omegapak 10 HP AC Drive bought here for $100
It was a little bit of a PITA, to put it mildly, as it had a very old fashioned control interface. But after some pain, printing out the manual, and going over things a dozen times, I am now at the point where the drive comfortably runs the motor, gives smooth acceleration, deceleration and all that.
As a result, this setup is exceptionally quiet and starts nicely and easily.
The next step would be to try to run it from single phase. (the drive is 3 phase rated)
My plan is as follows. This drive has two separate inputs: one for control circuit H1 and H2, and another for three phase input L1, L2, L3. It also has full amperage contacts for the DC bus, + and -.
So what I want to try, is this: feed DC bus directly, through + and -, from a completely separate rectifier and a huge 2,200 uF, 700V electrolytic capacitor. (two 2200 uF, 350V caps in series actually). Feed the control circuit H1/H2 from regular household 220v.
If I am right, and if it works, it would give enough juice to the DC bus to not phase fault during zero crossings.
I will see.