single phase VFD
single phase VFD
(OP)
We're testing a 110v single phase Variable Frequency Drive(VFD) connected to a single pump having randomly let's say: R= 10ohm, L= 50mH. and im putting these numbers to fiqure out the relationship between the output frequency from the VFD and the power consumption by the pump, so if u could make a curve or giving me the equations used in here i'll be thankfull.
Regards,
Salman
Regards,
Salman





RE: single phase VFD
What type of motor are you using and what starting method is used?
What type of pump are you using. The power consumption characteristics of a centrifugal pump versus a positive displacement pump are quite different.
The power demanded by the pump depends on the pump speed and the dynamic head.
The power demanded by the motor is the power demanded by the pump plus the motor losses.
The effective impedance of the pump will change as the slip frequency changes.
Measure the power into the VFD with a Watt meter.
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: single phase VFD
OPTIDRIVE
AC Variable Frequency Drive
this is the type im using and it's connected to a single phase pump in a water and oil flow loop. Id like to make things theoretically (deponds on the power consuption, voltage and Impedance of the pump, .. not to the total head ft or flow rating) before taking measurements.
regards,
Salman
RE: single phase VFD
If it is a positive displacement pump, expect the power to vary directly with speed, so at 1/2 speed, it will require 1/2 power.
The only othe power consumption issue will be the conversion efficiency of the VFD and the motor efficiency, both of which will drop slightly with speed. Expect the VFD to be 97% eff at full speed, maybe 90% worst case below 50% speed (but remember, the power has dropped too, so it's a higher loss percentage of a lower value). The motor efficiency is all about the motor specs, but expect that to drop similarly.
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RE: single phase VFD
RE: single phase VFD
xnuke
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RE: single phase VFD
Keith Cress
kcress - http://www.flaminsystems.com
RE: single phase VFD
we here are looking for curves, Powere vs frequency from the VFD, impedance of the pump vs frequency from the VFD. thanks you anyway and if some one could help me with this that's would be great.
Regards,
Salman
RE: single phase VFD
Hope you understand what I want.
Regards,
Salman
RE: single phase VFD
It's all about what the pump is pumping. If it was molasses you can see it would take more power than if it's water. Also, the speed of the pump while pumping whatever it is GREATLY affects the power required. The VFD has to supply whatever that power is - not the other way around. The VFD doesn't dictate the power.
So here we seem to be having you asking what the power will be based on the frequency.
To answer this you need the pump curve from the pump's specification. Then you need to understand the resistance presented by the plumbing of your piping system. You apply THAT to the pump's data sheet showing it's operating curve and from that you see what power the pump will be demanding from the motor at any particular speed. From that you can make your own chart showing the required power delivered by the VFD verses any particular speed you command.
Do you understand this? Did I make it clear enough?
Keith Cress
kcress - http://www.flaminsystems.com
RE: single phase VFD
RE: single phase VFD
If you run a motor at a fixed frequency, the current will depend on:
The load.
The no-load losses.
The load losses.
The load may vary greatly, as Itsmoked points out, the load presented by a pump may vary greatly depending on the application.
You may work backwards from the current and the voltage to determine an impedance at one point in time, but that is more dependent on the load than on the motor characteristics.
For now, forget impedance.
Bill
--------------------
"Why not the best?"
Jimmy Carter