Less suction pressure on Blower after Star-delta starter replaced by VFD

A dust collector blower fan motor 18kW, previously run by a star-delta starter, has been replaced with a VFD( Brand: LS, Model: SV-iP5A). Our intention was to save energy by lowering the Frequency SP. The VFD has been set to V/F control mode.
But since the installation of VFD, the vacuum pressure dropped significantly even at 50Hz(Line Frequency). 18kW motor is taking current of about 34A. I could further increase the frequency which would increase Amps eventually motor might get damaged.
One thing I have noticed that the output voltage of VFD is only 360V at 50Hz although my line voltage is 415V.
Some related parameters that I have set are as follows:
FU1-40 V/F Pattern: Linear
FU1-50 Rated Voltage: 415
FU1-31 Base Frequency: 50
FU2-60 Control Mode: V/F
FU1-49 Input Voltage Adjustment: 86%
The last parameter stated above (FU1-49), I don’t know it function. I have tried increasing and decreasing between 73-115%. No improvement on output voltage or suction pressure.
As per my knowledge, blowers, pumps etc. load directly square proportional of its angular velocity/freq.
Why I am getting less suction pressure than previous even at 50Hz?
Why the output voltage is less? Is voltage responsible for less pressure?
Please guide me on this.

Thanks

That's not a complete part number for the VFD. What is the nameplate information from the fan motor?

Also, measure the input voltage to the VFD.

Dravik said:

Also, measure the input voltage to the VFD.

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Input Voltage Measured. 410V

Just curiosity but 415V times .86 (FU1-49)=356 aprox 360V, I was thinking that maybe you have to turn off drive to accept new values.
Maybe I'm wrong.

Check the following
FU1-29 - Should match your line input frequency
FU1-30 - Should match the motor's frequency

Dravik said:

Check the following
FU1-29 - Should match your line input frequency
FU1-30 - Should match the motor's frequency

Click to expand...

They both are 50Hz and set as it is.

Is the motor still wired in a delta configuration?

Check your RMP

You may be in a current limit mode and not breaking into full run mode. If you are in v/hz mode and 360v "I bet your freq is down by that % = speed is down = suction down

Probably a dumb question, but is the motor still rotating the correct direction?

Another question... What are you measuring the VFD output with? or are you looking at its display for output voltage?

A run of the mill multi-meter can't deal with a VFD output.

And another... did you measure the actual shaft speed of the motor? At "50 Hz", is it running nameplate speed? You might be going into a current limit situation on the drive, reducing the actual output.

brian123 said:

probably a dumb question, but is the motor still rotating the correct direction?

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+ 1

If tthe motor is actually spinning at 50hz, the suction pressure should match the previous DOL values. Eitther something else in the process changed (not related to the vfd install) or the motor is not actually spinning at 50hz.

Have you verified all other aspects of the process are the same and that the motor is actually spinning at 50hz?

OkiePC said:

Is the motor still wired in a delta configuration?

Click to expand...

Yes...Motor in Delta Config.

Your drive is most certainly going into current limit and the fan is not running at 50Hz. Simple physics.

On the fixed voltage starter you had before, what was the current limiting device. Electronic or Mechanical overloads? What was their rating?

What is the current limiting setting on the drive? Not familiar with your drive, but most have independent current limit settings other than just the FLA nameplate setting.

What Accel rate do you have the drive set to?