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Friction

Model of angular velocity dependent friction losses  Description The Friction component models friction losses. For stability, at low speeds the torque is linear with respect to velocity. At higher speeds, a power law is used. Fig. 1: Friction loss torque versus angular velocity for ${p}_{\mathrm{\omega }}=2$ To neglect friction losses, set ${P}_{\mathrm{ref}}=0$ (this is the default). Equations $\mathrm{\tau }=\left\{\begin{array}{cc}0& {P}_{\mathrm{ref}}\le 0\\ -{\mathrm{\tau }}_{\mathrm{ref}}{\left(\frac{\mathrm{\omega }}{{\mathrm{\omega }}_{\mathrm{ref}}}\right)}^{{p}_{\mathrm{\omega }}}& {\mathrm{\omega }}_{\mathrm{linear}}\le \mathrm{\omega }\\ {\mathrm{\tau }}_{\mathrm{ref}}{\left(-\frac{\mathrm{\omega }}{{\mathrm{\omega }}_{\mathrm{ref}}}\right)}^{{p}_{\mathrm{\omega }}}& \mathrm{\omega }\le -{\mathrm{\omega }}_{\mathrm{linear}}\\ -\frac{{\mathrm{\tau }}_{\mathrm{linear}}\mathrm{\omega }}{{\mathrm{\omega }}_{\mathrm{linear}}}& \mathrm{otherwise}\end{array}$ $\mathrm{\tau }={\mathrm{\tau }}_{\mathrm{support}}=-{\mathrm{\tau }}_{\mathrm{flange}}$ ${\mathrm{\tau }}_{\mathrm{ref}}=\frac{{P}_{\mathrm{ref}}}{{\mathrm{\omega }}_{\mathrm{ref}}}$ $\mathrm{\phi }={\mathrm{\phi }}_{\mathrm{flange}}-{\mathrm{\phi }}_{\mathrm{support}}$ $\mathrm{\omega }=\stackrel{.}{\mathrm{\phi }}$ ${\mathrm{\omega }}_{\mathrm{linear}}=0.001{\mathrm{\omega }}_{\mathrm{ref}}$ $\mathrm{lossPower}=-\mathrm{\tau }\mathrm{\omega }$ Variables

 Name Units Description Modelica ID $\mathrm{\phi }$ $\mathrm{rad}$ Angle between shaft and support phi $\mathrm{\tau }$ $Nm$ Torque tau $\mathrm{\omega }$ $\frac{\mathrm{rad}}{s}$ Relative angular velocity of flange and support w $\mathrm{lossPower}$ $W$ Loss power leaving component via heat port lossPower Connections

 Name Description Modelica ID $\mathrm{flange}$ Shaft end flange $\mathrm{support}$ Housing and support support $\mathrm{heatPort}$ heatPort Parameters General Parameters

 Name Default Units Description Modelica ID Use Heat Port $\mathrm{false}$ True (checked) enables heat port useHeatPort Losses Parameters

 Name Default Units Description Modelica ID ${P}_{\mathrm{ref}}$ $0$ $W$ Reference friction losses with $\left|\mathrm{\omega }\right|={\mathrm{\omega }}_{\mathrm{ref}}$ PRef ${\mathrm{\omega }}_{\mathrm{ref}}$ $\frac{\mathrm{rad}}{s}$ Reference angular velocity wRef ${p}_{\mathrm{\omega }}$ $2$ $1$ Exponent of friction torque w.r.t. angular velocity power_w Modelica Standard Library The component described in this topic is from the Modelica Standard Library. To view the original documentation, which includes author and copyright information, click here.