 Sign-convention with torques on an axis? Options Hannes  Dec 6 2007, 09:46 AM Post #1 Member  Group: Members Posts: 29 Joined: 5-September 07 Member No.: 2,176 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_torqueSo how do I have to translate this into Modelica with its flow-variables for torques?Modelica.Mechanics.Rotational.Inertia tells me withJ*a = flange_a.tau + flange_b.tauthat 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*omegaIs that right?What astonishs me is the equation in Modelica.Electrical.Machines.BasicMachines.Components.AirGap*:flange_a.tau = -tau_electricalDo 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...Hannes    