VFD Operational Practices
VFD Operational Practices
(OP)
Need some opinions on best operating practices for a pump station where two pumps are fitted with VFDs and the third is constant speed.
The operators normally operate the two VFD pumps at 100% speed rather than operating the fixed speed pump and one VFD.
Isn't the operator's preferred mode burning up a lot of more kWhs over 1 VFD + 1 constant speed operation?
The operators normally operate the two VFD pumps at 100% speed rather than operating the fixed speed pump and one VFD.
Isn't the operator's preferred mode burning up a lot of more kWhs over 1 VFD + 1 constant speed operation?





RE: VFD Operational Practices
RE: VFD Operational Practices
"Our virtues and our failings are inseparable, like force and matter. When they separate, man is no more."
Nikola Tesla
RE: VFD Operational Practices
RE: VFD Operational Practices
"Our virtues and our failings are inseparable, like force and matter. When they separate, man is no more."
Nikola Tesla
RE: VFD Operational Practices
RE: VFD Operational Practices
"Our virtues and our failings are inseparable, like force and matter. When they separate, man is no more."
Nikola Tesla
RE: VFD Operational Practices
No doubt that the part load savings justify the VFDs but this is a base load plant.
Wasn't involve in the selection of 2 VFDs and 1 constant speed mototr but suspect that I would have advocated 1 VFD + 2 constant speed for this installation and saved the cost of the extra drives.
RE: VFD Operational Practices
RE: VFD Operational Practices
VFDs are being put onto fixed flow installations with the promise of energy savings. If the pump always has the same constant flow, it would be better to size the pump correctly and run it with a soft starter. This energy savings concept has conditional requirements. I advocate VFDs for variable flow requirements but question VFDs for fixed flow installations.
Best regards,
Mark Empson
http://www.lmphotonics.com
RE: VFD Operational Practices
If all you want is fixed speed operation, then plan for soft starters to remove most water hammer and that's it.
No reason to use VFD's for fixed speed pump applications except for some minor reasons.
Maybe the use of the VFD's here isn't fully utilized for the system. Maybe speed control still has to be implemented but no-one has realized the benefits yet.
Also agree with you cub3bead. I would have also just installed a single VFD and two fixed speed pumps. Once the VFD is at full speed, then bring on a fixed speed pump and back of the VFD and so for the 3rd pump aswell. Common line though.
This depends on your piping design too though and how the system is designed.
RE: VFD Operational Practices
A logic evaluation to get optimum initial cost, performance and operational efficiency seems necessary.