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.
I bought it without the motor, it had a 7.5 HP 58 year old motor that
I did not care for anyway, which gave me a nice price reduction from
the seller, who happened to be a super great guy.
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:
I have been working on powering this compressor from a VFD. I am
hoping to accomplish several things with a VFD:
1) Running from single phase
2) Quiet starts
3) 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
I decided to solve one problem at a time, and tried to use it from a
real three phase input (phase converter).
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.
- posted 13 years ago