This information is part of the Modelica Standard Library maintained by the Modelica Association.

The friction losses are considered by the equations

  tau / tauRef = (+w / wRef) ^ power_w    for w > +wLinear
- tau / tauRef = (-w / wRef) ^ power_w    for w < -wLinear

with

tauRef * wRef = PRef

being the friction torque at the reference angular velocity wRef. The exponent power_w is approximately 1.5 for axial ventilation and approximately 2.0 for radial ventilation.

For stability reasons the friction torque tau is approximated by a linear curve

tau / tauLinear = w / wLinear

with

tauLinear = tauRef*(wLinear/wRef) ^ power_w

in the range -wLinear ≤ w ≤ wLinear with wLinear = 0.001 * wRef. The relationship of torque and angular velocity is depicted in Fig. 1

Fig. 1: Friction loss torque versus angular velocity for power_w = 2

See also

FrictionParameters

If it is desired to neglect friction losses, set frictionParameters.PRef = 0 (this is the default).