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Ignoramus705

On 2007-10-23, Pete C. wrote:
Ignoramus705 wrote:

On 2007-10-23, Pete C. wrote:
wrote:

On Oct 23, 9:01 am, Ignoramus705
wrote:
The 10 HP compressor is now in my yard. Looking good, but needs a
little cleaning.

I will hopefully receive the VFD on Friday or so. It is a Siemens SED2
18.5 kW rated drive. Assuming it works, I have to set its parameters
and here's where I need a little bit of wisdom.

Specifically, my question is how do I set the acceleration ramp-up so
that it works nicely with the unloaders. My own thinking is that I
should accelerate slowly almost up to the speed when unloaders kick
in, and then accelerate as fast as I can once unloaders do kick in and
the pump starts pumping. Any idea what is the speed when unloaders
kick in?

thanks

i

Hi.
Just for reference, our 5 hp, 220 volt 3 phase, compressor seems to
have zero ramp up. At least it's not detectable when it starts. Seems
to go from zero to full speed instantly. The tank is 60 gal. So,
really don't think acceleration on your compressor should be a
consideration.

Best regards,
Paul

Presumably you're feeding your compressor "real" three phase power. When
using three phase from a VFD functioning as a phase converter from
single phase power in a residential setting a little soft start helps
reduce the lights dimming and SWMBO bitching.

My plan, to be exact, is to put this compressor on a VFD so that it
can be run without any phase converter. My setup features a 10 HP
compressor motor, 15 HP head (spun 33% slower), and a 25 HP rated VFD.

Just to be a little redundant, I did call Quincy today and gave them
my serial number etc, they confirmed that this is a 15 horsepower
head, properly slowed down so that it can be driven by a 10 HP motor.

So, I want the VFD to take 1 phase in, and to make 3 phase out for the
motor to run.

Um, that reply was to the other poster his 3ph compressor with no
VFD or soft start.

Yes, you are right.

Iggy - Are the unloaders speed or time controlled? If speed, your plan
sounds good, if time, get things up to speed in time for the unloaders
to kick in.

I would guess they are speed controlled.

Seems unlikely given the other replies.

Looks like I was wrong here, too.

Either way I doubt there will be much benefit to a ramp up of more
than 1 second. You can always put an amp probe on it and see what
peak current is with zero ramp up and at different ramp rates and
see what is the best fit.

1 second seemt to be the best all around spin up time, to me
personally. Not too slow, not too fast, does not startle people as
much and is gentle on everything.

i

1 Second is probably good, however if this is your winter project, some
peak amp numbers at different soft start rates would make an interesting
post...

I went through this once with my phase converter. I will report my
results once I get somewhere.

i