VFD Pumps
VFD Pumps
(OP)
Can anyone tell me what VFD pump is? Why do you use it? Can it be modeled in WaterCAD?
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RE: VFD Pumps
http://www.mcnallyinstitute.com/13-html/13-08.htm
RE: VFD Pumps
Its used in places where three phase is not available where you need three phase power to power a three phase pump. Normally, you would size the pump seperately and use a VFD to supply the 3 phase from the single source, but this is a cost-effective alternative.
RE: VFD Pumps
AC power is converted to DC power, then the DC supply altered, and then the DC is converted back to AC in order to control the speed of the motor. It doesnt convert 1phase to 3 phase.
The basics are shown here:htt
RE: VFD Pumps
RE: VFD Pumps
You can use them to slow a motor down and, if the motor is a pump driver, you will slow down the flowrate and reduce the differential head of the pump.
See "pump affinity" estimate equations to predict the results the decrease in rotational speed has on flow and head. The basic premises are,
The New_Flowrate = Old_Flowrate * New_Speed / Old_Speed
The New_Head = Old_Head * New_Speed^2 / Old_Speed^2
The New_Power = Old_Power * New_Speed^3 / Old_Speed^3
The relationships are valid where pump efficiency does not change and where system flowrate is also roughly proportional to the change in pump's differential head.
http://virtualpipeline.spaces.msn.com