saving power by using VFD instead of throttle valve

[usamaegypt]

Hi;
We have a fan drived by a motor 200 KW and has a throttle valve to control the flow. Most of the time the throttle valve opening is 30% . We would like to know how to calculate the power saving in case of replacing the throttle valve by frequency drive.
Best regards.

 

[quark]

Victor,

You have a constant volume flowrate application. Why can't you change the pumps? Is new pump+vsd cost less than new pump cost? BTW, what is the discharge pressure of the pumps?

Jraef,

It is a common practice to control fans with IGVs and VSDs simultaneously for better capacity control(pariticularly with centrifugal chillers). One advantage (worst case) with having dampers though we use VSDs is that when the VSD fails we don't risk our system to overload.

Regards,

 

[DickDV]

NI008, ask your ABB rep to run your system parameters on their energy analysis software.

The factory will have such software and it is remarkably accurate. (It is not designed as a sales tool) ABB's system engineers use the same program for their own calculations.

You will find immense savings, I assure you.

This sounds like a Medium Voltage job. Ask your rep about running these pumps sequentially with a single drive and PFC software (that's Pump/Fan Control). I don't know if it can be done in Medium Voltage but, below 600volts it works very well. Basically, as flow demand increases, the first pump speeds up until it reaches line frequency. At that point, the drive transfers this first pump to across-the-line operation and begins accellerating the second pump. At maximum flow demand, both pumps are at full speed. At flow demand falls, the drive unwinds the whole process down to the first pump running at minimum speed. Each time the system is restarted, the lead pump is changed to balance pump wear.

It sounds like the perfect setup for your system if it can be done at MV.