VFD and a centrifugal pump??
VFD and a centrifugal pump??
(OP)
Hello all,
I am an electrician in a can manufacuring plant with a question. Our requirements for cooling water used to be around 100gpm for our ironers. They have done several modifications and now think that we need to increase the flow. I agree that they do need to increase the flow but our superintendant wants to know if we can regulate the flow of a bigger pump and motor with a Variable Freq. Drive.
Supposedly we are replacing a 100gpm pump and a 5hp motor with a 200gpm pump and 10hp motor and he wants to be able to regulate flow by changing pump speed. Is this something you should do with a centrifugal pump??
Thanks,
Kyle
I am an electrician in a can manufacuring plant with a question. Our requirements for cooling water used to be around 100gpm for our ironers. They have done several modifications and now think that we need to increase the flow. I agree that they do need to increase the flow but our superintendant wants to know if we can regulate the flow of a bigger pump and motor with a Variable Freq. Drive.
Supposedly we are replacing a 100gpm pump and a 5hp motor with a 200gpm pump and 10hp motor and he wants to be able to regulate flow by changing pump speed. Is this something you should do with a centrifugal pump??
Thanks,
Kyle





RE: VFD and a centrifugal pump??
RE: VFD and a centrifugal pump??
RE: VFD and a centrifugal pump??
RE: VFD and a centrifugal pump??
RE: VFD and a centrifugal pump??
RE: VFD and a centrifugal pump??
RE: VFD and a centrifugal pump??
RE: VFD and a centrifugal pump??
W.R.T SPEED CHANGE (AS OPPOSED TO IMPELLER DIAMETER, FOR INSTANCE)
Q1/Q2 = (S1/S2)
HD1/HD2 = (S1/S2)^2
HP1/HP2 = (S1/S2)^3
S = SPEED
Q = FLOW RATE
HD = HEAD
HP = HORSEPOWER
VFD's have been used for years to control centrifugal devices such as fans, chiller compressors, and pumps. In the "early" days a marketing ploy was to sell "energy conservation" and VFD/PUMP combo.
I concur you should take a close look at the pump curves and the application. Otherwise, you are "shooting in the dark" at the process outcome. If you are unfamiliar with pump curves, system curves, etc., most drive vendors are glad to help with such applications.
RE: VFD and a centrifugal pump??
Using VFD's you can control the speed of the motor and hence the flow of the pump. The advantage lies in the fact that power decreases by the cube of the speed decrease. Thus a 5% (0.95) speed decrease will cause the power requirement to decrease by cube of the decrease (0.95x0.95x0.95 = 0.86). This is provided that the motor is suitably matching the pump (10HP for 200GPM @ a certain head) and also make sure that the motor you buy is an inverter rated motor.
But you have to check the economics behind this, since the power decrease in a 10HP motor would be lot less than the investment done in buying an inverter and an inverter rated motor, even if you are considering a couple of years for payback.
RE: VFD and a centrifugal pump??