On Oct 29, 1:13 am, Ignoramus32225 ignoramus32...@NOSPAM.
32225.invalid wrote:

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".

I assume V and F in that case refer to voltage and frequency. You have
to reduce the voltage as you reduce the frequency, because the motor
has a lower impedance at lower frequencies as it is predominantly an
inductive load.

A "positive displacement pump" is one where fluid cannot leak
backwards through the pump. So a compressor is a positive displacement
pump, but a fan would not be.

It sounds like you probably have a problem with the settings on the
VFD.

Best wishes,

Chris