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> Sign-convention with torques on an axis?
post Dec 6 2007, 09:46 AM
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Hi there again!

I've got a question about the equation of "conservation of angular momentum". Normally it's (in words):

cause = driving_torque - load_torque = effect = acceleration + friction + reset_torque

So how do I have to translate this into Modelica with its flow-variables for torques?

Modelica.Mechanics.Rotational.Inertia tells me with

J*a = flange_a.tau + flange_b.tau

that positive load-torques that "flow into" the component (motor) increase the velocity. So adding friction and a driving torque (caused by a combustion engine or electrical motor) and neglegting the reset_torque I get:

flange_a.tau + flange_b.tau + inner_torque = J*der(omega) + beta*omega

Is that right?

What astonishs me is the equation in Modelica.Electrical.Machines.BasicMachines.Components.AirGap*:

flange_a.tau = -tau_electrical

Do I interpret this correctly when I see in it the equation above with flange_b.tau=0 and J*der(omega)=0 and beta*omega=0???

Thanks for your comments...

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