"Ned Simmons" wrote in message
...
On Sun, 05 Oct 2008 23:11:20 -0400, GeoLane at PTD dot NET GeoLane at
PTD dot NET wrote:

I'll be picking up my Bridgeport 2 HP 2J in a couple of weeks, so
it's time to start working on a rotary phase converter.

Others have given you good advice on rotary phase converters, but I'll
give you my take. Having run Bridgeports on rotary converters, static
converters and VFDs, a rotary would be my last choice. A VFD is much
more convenient, even with a 2J variable speed head, and a static
converter is more than adequate. RCM dogma says that you can't plug
reverse a BP with a static converter, but I did it for many years, as
does a friend of mine with 3 mills in a commercial shop.

What is "plug reverse"?

The reversing issue on a static converter:

On static conversion, the motor can be reversed via the BP switch, as long
as the leads being interchanged are L1 and L2 -- or so I think. AND, of
course, the starting caps placed between L1-L3 or L2-L3.

The problem with static converters is that they seem to strain the motor
after startup, unless they are switched out, and balanced run capacitors are
switched in.

But if this is done, then I agree, static conversion, at least for one
motor, may be preferable -- altho, you will have to de-rate that motor.

Another 3 ph motor elsewhere on the grid would help "re-rate" the motor, but
then you have the curious scenario where the statically converted motor is
acting like an rpc!

So I would say that if you only have one motor, and you don't mind de-rating
it, static conversion would be preferable to an rpc.

But otherwise (1 motor, no de-rating), an rpc would proly make more sense.
I'm thinking of statically converting a compressor motor.

AND, interestingly enough, I have a residential central air unit that I just
discovered has a 3-ph compressor with... you guessed it.... static
conversion!!

Which is possibly why the compressor is so goddamm noisy, cuz of the
inherently imbalanced start capacitors, that are never switched out, of
course. Will be a chore to wire this up properly....

I've had two VFD's for some time, but haven't hooked them up yet -- thinking
of making a kalamazoo 9x13 hydraulic the first guinea pig -- but then I
could only put the blade motor on the VFD.

I'm still in rpc-mode.
VFDs, tho, are theoretically Da Bomb.
--
DT



--
Ned Simmons