This is because with rotating loads, the required motor torque is directly related to the inertia of the load. Note that inertia includes the inertia of the load a fan, for example plus the inertia of the motor and any other rotating components such as couplings or pulleys between the motor and the load. Notice that the inertia equations for induction motors use weight which is a force rather than mass.
R is the radius of the object, from its center to its outer edge. Poor fan installation can cause early failure, which is likely to be costly in terms of the fan itself, as well as the potential loss of production time. As with other rotating machinery, proper fan operation usually requires correct drive alignment, adequate foundation characteristics, and true fit-up to the connecting ductwork.
In a different context, fan start-up can refer to the acceleration of a fan from rest to normal operating speed. Log In. So WR 2 would be inaccurate for a motor rotor then. That would explain why we see WK 2 used. Someone picked out the wrong reference, probably learned it in the same textbook I did way back when and like me, repeated it. Dealing with motors, not cylinders, I don't see it used often and have never needed to really know the difference since then because I always knew what they meant when using the term incorrectly as it turns out for rotors.
Today, I learned there is a difference. Now I can be even nerdier when correcting people in the future! To use the formula for a cylinder, the density of the cylinder must be the same at every point.
If you are using units of weight e. But you must be really careful if you start using expressions for MOI like those above. I've seen people get very wacky results if they leave that out.
People also often screw up if they use non-official units of "pounds-mass" or "kilograms-force" as they try to convert between SI and English.
Again, they are usually off by a factor of "g" if they are not careful when they do this. It is the equivalent unit to the metric kilogram.
In this overlay the shaded area reflects the accelerating torque available from the motor to drive the pump. In other words, this is the point of maximum pump speed while powered by this motor. HP is a combination of torque and speed RPM , with 1 HP equal to foot pounds per second, or 33, foot pounds per minute. Torque at zero flow is especially important for pumps with axial flow or propeller designs. The torque-speed curve of such pumps is such that the highest HP, and therefore the highest torque, is required at zero flow.
An axial-flow pump must be paired with a motor with adequate HP to get the pump moving. The higher the pump inertia, the longer the motor will take to start the pump and bring it to full load speed. This is significant because motors draw current to bring pumps up to speed.
If a motor directly drives the pump, the values of the pump and pump-motor coupling inertias are the same regardless of pump speed.
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