Update 1, Siemens SED2 VFD / Quincy 10 HP compressor troubles
- From: Ignoramus3971 <ignoramus3971@xxxxxxxxxxxxxxxxxxx>
- Date: Mon, 29 Oct 2007 07:22:10 -0500
[top-posting to keep information better organized]
I spent some time with the drive last night.
1) Changing V/f curve does seem to change things a little, but not much.
2) I set all sorts of parameters like "acceleration boost", to the
highest values, without much success.
3) Under load, the input voltage (from utility) does not change
much. So voltage drop is not an issue.
4) When starting, the compressor starts spinning, then hits an
"obstacle", and comes to complete or almost complete stop.
I now think that at last part of the problem, as mentioned by other
people wrt phase converter, is with "unloaders". I do not think that
they are correctly functioning.
At the very least, I want to try altering their function so that the
compressor spins freely, such as when running with a gas motor that is
idling. It would, obviously, be for test purposes, but I want to now
try this with the compressor NOT pumping any air.
With the limited time and understanding that I had yesterday, I was
unable to do so. I even disconnected some air lines that led to the
unloader adjustment box. To no avail, nothing has changed.
I will read the manual today and see how I can try to disable
unloaders. (disable in the sense of preventing the compressor from
pumping air)
This story is more difficult than I thought it would be, but I stil
have some optimism.
i
On 2007-10-29, Ignoramus32225 <ignoramus32225@xxxxxxxxxxxxxxxxxxxx> wrote:
I tried connecting the VFD to the compressor. The VFD is a 18.5 kW (25.
HP) rated Siemens SED2 VFD. Its target market is HVAC. The compressor
is a 10 HP motor.
It was kind of unsuccessful. I made quite a few observations.
1) The motor, when VFD turns on, only spins at maybe 60 to 90 RPM. And
struggles to turn the compressor.
2) The VFD has no troubles spinning up an unloaded 1 HP motor (just
for test).
3) I measured DC bus voltage when the VFD was powering up the 10 HP
motor, it was about 220v.
4) I used a straight piece of 10 ga wire instead of a DC choke to
connect the DC bus.
5) If I measure voltage on the output, with my nice multimeter
(knowing that I should not trust the result too much due to square
wave), I get something like 70-90 volts instead of 220. That's what
the read on panel reads if I set it to display voltage.
Logically, a 25 HP VFD should spin up the 10 HP motor.
I looked into the manual, available at
http://igor.chudov.com/manuals/
and found reference to parameter 1300, V/F curve. It talks about
different selections, such as linear V/F, parabolic etc. It says that
linear V/F is better for constant torque and "positive displacement
pumps".
Due to family stuff, I had no time to actually try changing this, does
it sound as though this could solve it? The wikipedia Pump article
seems to imply that my piston compressor is a positive displacement
pump.
Anyway, it was a somewhat frustrating day in this respect. I will
followup to this once I try it in an hour or so.
i
- References:
- Siemens SED2 VFD / Quincy 10 HP compressor troubles
- From: Ignoramus32225
- Siemens SED2 VFD / Quincy 10 HP compressor troubles
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