Speed Torque Curve

[kflee0]

As a pump engineer, I always asked to provide pump speed torque curve to the motor guy but I never know the real reason behind. I figure it must have something to do with motor at start-up, when the pump shaft gets hammered by a large amount of starting torque.

I guess my question is how do you tell if it's ok or not by checking the pump S-T curve and motor S-T curve to avoid pump broken shaft or burn up motor. Does the torque of your motor have to be always more than the torque of your pump at the range of zero rpm to the steady state operation or vice versa???? Can you give us some comment on this?

Also, there appears to be some different thoughts on this between the engineers in my firm. Some thought that start up is the worst case scenario for the shaft and not steady state operation but others thought the opposite way. What are your thought about this?

 

[electricpete]

At any given speed, motor torque minus pump torque is the accelerating torque.

Having motor torque exceed pump curve at every speed is a necessary but not sufficient condition for successful motor starting. If the pump curve comes closer to the motor curve, less accelerating torque is available and the startup takes longer. Longer starting time means more heating of the motor which it may not be able to tolerate. (Note the heating is not soley a function of starting time).


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[BigInch]

Start up is usually the worst case, as the fluid in the system is also experiencing maximum accelerations which can be aggravated further when attempted against high static heads.

BigInch-born in the trenches.

http://virtualpipeline.spaces.msn.com

 

[Artisi]

Have a look at the following link or go to google or

http://www.ask.com

and type in -" pump speed torque curve "- you will come up with a lot of info.

http://www.engineeringtoolbox.com/pumps-speed-torque-d_1114.html

 

[kflee0]

Thank you all for your help.