Variable Torque Loads

[ulrichj]

I am looking at modeling typical industrial loads. Variable torque loads seem to be the most challenging and finding information on the behavior of these loads specific to my needs is not that easy. Does anybody have any suggestions for good resources on the mathematical modelling of these with a view to developing software? even if someone has an individual example of pertaining to a particular fan or pump it would help.

 

[electricpete]

As a first approximation:

Pumps and fans should follow torque proportional to speed^2.
Find the torque associated with the rated power at rated speed and ratio from there.

Maybe that part is not intuitively obvious... but as a double-check:
Power=Speed*torque ~ Speed^3. This is well-know pump law.

One of the reasons that is an approximation is that a particular pump may not consume rated power at rated speed due to different fluid density than assumed. There is a simple relationship between power and fluid density...

I'm thinking that power varies directly proportional with density, but you should doublecheck me on that one.

 

[Marke]

In some cases, you will also need to overcome some sticktion at start so you get an inital higher torque requirement to get things moving. Mark Empson

http://www.lmphotonics.com