On Mon, 6 Oct 2008 11:43:28 -0400, "DrollTroll"
wrote:


"Todd Rich" wrote in message
...
DrollTroll wrote:
Awl --

With single phase, what are the pro's/cons with having a 3 ph compressor
motor with starting caps, vs swapping it out for a single phase motor?

The tradeoff I see is a wiring pita vs. the grunt/mechanical pita and $$
of
a single phase motor, with likely a modified mounting.

I would like to put the starting caps/running caps on relays, that switch
in/out, as well.

How big is it, and have you considered a VFD running your 3 phase motor
off of single phase power?

No, I hadn't. But it is an idea. About 5 hp.

Certainly caps will be cheaper, but wiring relays, start/run is going to be
a pain as well.
Plus, I will have to de-rate the motor, and possibly put a smaller pulley on
it.

Keep in mind that this is a scenario where the motor is starting under
near-full load, which might be some electrical wear/tear on a VFD.

At least I *think* it is starting under full load (tank pressure).
Is there a way to set up an air compressor so that the motor starts under no
load? Only with a clutch, I would imagine, or "almost no-load", where some
vent bypasses the compressor head to air, or sumpn, and then closes.

So much drama....

Many (if not most) compressors do not start under full load. There is
an "unloader" in either the pump output or in the controller.