Hello, I need to supply the exact value for pump and motor inertia for a transient simulation but I´m not clear as to which definition is used by Hammer, as some authors use diameter and others use radius in the definition.
We are modeling a pump driven by a Weg motor, with Inertia of the order of 33,000 lb ft^2, which is rated for 3710 kW at 382 rpm. If I use the calculator to estimate the total inertia (pump and motor) I get 4947 kg m2 or 117000 lb ft^2 or about 3.6 times larger than the supplied value of the manufacturer (granted, without pump, which we estimate to be about 10% of the motor, so it shouldn´t affect the estimate so much).
My question is, if the manufacturer is using 1/2 mR^2 = 33,000 lb ft^2 for inertia, should I enter a value of about 1.1x this value? What may be the cause of the large difference with the value estimated by the calculator?
Thank you in advance!
Hello Juan,
HAMMER uses radius for the moment of inertia (WR^2). This link has details on some of this. If you information from the manufacturer, I would recommend just using that value rather than using the calculator.
Regards,
Scott